SYMPOSIUM I

2:00 PM *I2-S3.1 (invited)
Analysis of Microstructure-Transport Relationships in Nano-Ionics for Energy Conversion Applications. (#763) Nicola H. Perry, Ted C. Yeh, Thomas O. Mason; Department of Materials Science and Engineering and Materials Research Institute, Northwestern University, Evanston, Illinois, USA.

Nano-ionics show promise for more efficient and reliable low temperature energy conversion technologies, e.g., as electrolytes and electrodes in solid oxide fuel cells. One challenge has been how to properly characterize grain boundary vs. grain core transport contributions in nanocrystalline electroceramics. The venerable "brick layer model" (BLM) for analyzing the AC-impedance response of polycrystalline ceramics is now approximately 40 years old. The present work updates the BLM family of models by introducing a nano-Grain Composite Model (n-GCM). Unlike the standard BLMs, the n-GCM is applicable to the nanoregime of grain sizes. A fortuitous agreement with the Maxwell-Wagner/Hashin-Shtrikman (MW/HS) effective medium model, for which a closed-form solution exists, permits reliable extraction of local grain core vs. grain boundary properties (electrical conductivities, dielectric constants), including grain boundary (space charge) widths. Case studies have been made on a range of nano-ionics for SOFCs, including cerium oxide, yttria-stabilized zirconia (YSZ), tetragonal zirconia polycrystals (TZP), and (Sr, Mg)-co-doped lanthanum gallate (LSGM). In the case of nanoscale YSZ, a significant enhancement of local grain boundary conductivity was observed. In addition, grain boundary (space charge) widths were obtained that are in good agreement with literature values. Ramifications for the use of nano-ionics in intermediate-temperature SOFCs will be discussed. The general applicability and limitations of the n-GCM will also be presented.

2:30 PM I2-S3.2
Charge Transfer at the Oxygen/Zirconia Interface. (#696) Tadeusz Bak, Centre for Materials Research in Energy Conversion, The University of New South Wales, Sydney, Australia.

The present paper describes the high temperature Kelvin probe and its application for the determination of the charge transfer at the bi-phase oxygen/zirconia interface. This technique is based on the measurement of work function change during oxidation or reduction at elevated temperatures. This paper will report the work function measurements of polycrystalline yttria-stabilised cubic zirconia (10Y-ZrO2) during isothermal oxidation at temperatures ranging between 873 K and 1173 K. The experimental data will be considered in terms of interface phenomena, such as oxygen chemisorption and oxygen incorporation into the lattice and the related electrical effects at the outermost surface layer. It was found that oxidation at 1173 K, results in rapid oxygen incorporation into the zirconia lattice while the surface is free of oxygen chemisorption. Oxidation at 1073 K and lower temperatures results in the formation of an oxygen chemisorption-induced surface charge which prevents oxygen incorporation.

2:45 PM I2-S3.3
In-Situ Surface Photovoltage Spectroscopy of TiO₂ Thin Films in an Aqueous Environment. (#437) David Stephen Warren, Department of Chemistry, University of Otago, Dunedin, New Zealand.

Titanium dioxide is a chemically stable, wide band gap, n-type, semiconductor that has been the focus of much research since Fujishima[1] first reported the use of a TiO2 electrode to decompose water using light (photocatalysis). Photocatalysis relies on the illumination of wide bandgap semiconductors to generate electron/hole pairs that can initiate a series of redox reactions at the photocatalyst surface. Photocatalysis has been studied using a variety of techniques including atomic force micrsocopy, high resolution electron energy loss spectroscopy, gas chromatography, high pressure liquid chromatography, as well as ultra violet and infrared spectroscopies. The latter technique has been used to monitor in-situ chemical changes induced by substances absorb on to the photocatalyst and then follow subsequent reactions occurring upon illumination. There have also been several reports of IR spectral features assigned to electronic sources such as trapped charge carriers. The sampling geometry of attenuated total reflection IR spectroscopy (ATR-IR) has proved to be especially well suited to in situ monitoring. A flow cell mounted above a polycrystalline film deposited on the surface of an ATR prism allows species to be adsorbed on to the film and the process monitored an evanescent wave penetrating a few microns from the ATR prism surface. This leads to minimal spectral interference from solution species and has proved successful using a wide range of adsorbates[2-5]. Surface photovoltage spectroscopy (SPS) is a well established contactless technique that has been used to study surface, bulk and interfacial properties of a wide range of semiconductors and semiconductor devices[6]. The commonest method is the Kelvin probe technique, where the difference between the work functions (contact potential difference, CPD) of a vibrating metal reference electrode and the semiconductor are measured. These measurements are usually carried out either under an ambient gas or vacuum. There have been very few studies involving CPD measurements in a liquid/aqueous environment[7]. We have recently reported an apparent conductor type reversal in polycrystalline films formed from small anatase particles.[8] This apparent type conversion appeared to be related to adsorbed surface water. As an extension of that work, we report here the behaviour of TiO2 polycrystalline films in an aqueous environment using a combination of in situ ATR-IR and SPS measurements. The latter being achieved using a flow cell similar to that used in the ATR-IR data collection. Details of this flow cell and its potential use in monitoring films in aqueous environments will be discussed. [1] A. Fujishima, K. Honda, Nature (London, United Kingdom) 238 (1972) 37-38. [2] S.A. Dickie, A.J. McQuillan, Langmuir 20 (2004) 11630-11636. [3] Z. Gao, P.J. Bremer, M.F. Barker, E.W. Tan, A.J. McQuillan, Applied Spectroscopy 61 (2007) 55-59. [4] S.J. Hug, Journal of Colloid and Interface Science 188 (1997) 415-422. [5] K.A. McComb, D. Craw, A.J. McQuillan, Langmuir 23 (2007) 12125-12130. [6] L. Kronik, Y. Shapira, Surface and Interface Analysis 31 (2001) 954-965. [7] L. Chai, D. Cahen, Materials Science & Engineering, C: Biomimetic and Supramolecular Systems C19 (2002) 339-343. [8] D.S. Warren, Y. Shapira, H. Kisch, A.J. McQuillan, Journal of Physical Chemistry C 111 (2007) 14286-14289.

3:00 PM I2-S3.4
Heterovalent Substituted NASICON-like Phases in RMPO₄-AM₃PO₄ Quasibinary System (RM = Sc, Yb and In; AM = Na and Li). (#491) Andrey Novoselov¹, Anna Potapova¹, Irina Smirnova¹, Felix Spiridonov², Galina Zimina¹; ¹Department of Chemistry and Chemical Engineering for Rare and Dispersed Elements, Lomonosov Moscow State Academy of Fine Chemical Technology, Russian Federation ; ²Lomonosov Moscow State University, Russian Federation.

The discovery of Na_1+xZr₂Si_xP_3-xO₁₂ (later named as NASICON-NAtrium SuperIonic CONductor) by Hong, Goodenough and Kafalas in middle 1970th made a tremendous contribution to development of solid state ionics [1,2]. High alkali ion-based conductivity and good cation-exchange properties of NASICON family members, as well as fast growing market of potential applications such as battery electrodes, fuel cells, chemical sensors and membranes for radioactive waste disposal, have motivated advances in NASICON structurally related compounds. NASICON-like phases in RMPO₄-AM₃PO₄ quasibinary system (RM = Sc, Yb and In; AM = Na and Li) seem to be very promising compositions of high ionic conductivity. Nevertheless, these compounds have complex polymorphism that makes it difficult to obtain NASICON-like ceramics of high phase homogeneity. We have recently reported the way to improve phase stability by solid solutions formation in ScPO₄-Na₃PO₄-Li₃PO₄ quasiternary system, but obtained data on ionic conductivity were still far from expected [3]. Looking for the ceramics of better conducting performance, we have investigated solid solutions in InPO₄-Na₃PO₄ as well as heterovalent Zr-substituted YbPO₄-Na₃PO₄ and ScPO₄-Na₃PO₄ quasibinary systems. Samples were prepared through every 2-10 mol%, annealed during 200-400 h at 800, 850, 900 and 1050°C, quenched in liquid nitrogen and then were subject of powder X-ray diffraction analysis. Ionic conductivity was measured with impedance spectroscopy at 300°C. Ionic conductivity of a solid solutions sample Li_3(1-x)In_2+x(PO₄)₃ (x = 0.68) was measured to be 0.44•10 ² S/cm. This value is comparable to that of well-known NASICON-like Na₃Sc₂(PO₄)₃. We suggest heterovalent substitution according to equation: 3Na⁺ = In³⁺ + 2ν, where ν - is a vacancy in Na⁺ cationic sublattice. Substitution of Zr⁴⁺ (up to 7 mol%) for Yb³⁺ in Na₆Yb₃(PO₄)₅ leads to formation of solid solutions. We propose the following substitution scheme: Yb³⁺ + Na⁺ = Zr⁴⁺ + ν. As-formed vacancies in Na cationic sublattice promote movement of Na cations resulting into values of ionic conductivity of 1.6•10^-2 S/cm for Zr-substituted (7 mol%) Na₆Yb₃(PO₄)₅ sample. Ionic conductivity of 10 mol% Zr-substituted Na₃Sc₂(PO₄)₃ sample was measured to be 3.18•10^-1 S/cm, which is one order of magnitude higher than that of pure Na₃Sc₂(PO₄)₃. Heterovalent Zr-substitution was shown to be a viable approach to obtain compositions with high ionic conductivity. We will present the obtained results, demonstrate established regularity of composition-structure-properties and discuss techniques of obtaining high conducting NASICON-like phases in a heterovalent substituted phosphate system. [1] H. Y-P. Hong, Mater. Res. Bull. 11 (1976) 173-182. [2] J. B. Goodenough, H. Y-P. Hong, J. A. Kafalas, Mater. Res. Bull. 11 (1976) 203-220. [3] M. Zhuravleva, R. Zakalyukin, A. Novoselov, G. Zimina, Mater. Res. Bull. 41 (2006) 2065-2069.

3:15 PM I2-S3.5
Observation of Hydrogen Distribution in Proton Conducting Oxides with Tritium Autoradiography. (#1128) Kenichi Hashizume, Yusuke Oki, Hiroshi Tagami, Teppei Otsuka, Tetsuo Tanabe; Department of Advanced Energy Science and Engineering, Kyushu University, Fukuoka, Japan.

The present work is devoted to visualizing of hydrogen distribution in a proton conducting material, Ba2In2O5, with using tritium autoradiography technique (TARG), which has been applied to show tritium (hydrogen) accumulation on metal surface and/or local surface structures such as grain boundaries and inclusions. A disc-shaped Ba2In2O5 specimen (8 mm in diameter and 1mm in thickness) was prepared with a conventional solid state reaction method using BaCO3 and In2O3 powders as starting materials. Tritium was loaded into the specimen by a gas absorption method under 3 kPa of tritiated water vapor (T/H ~ one-millionth) at a temperature ranging from RT to 873 K for 1 hr. After tritium loading, the surface of the specimen was polished with abrasive papers and Al2O3 powders, and etched by a HF/HNO3 solution for easy observation of grain structures. Then, the specimen surface was coated with a thin collodion film and a monolayer of nuclear photographic emulsion of AgBr in a photo darkroom. The photographic emulsion was exposed to tritium ? electrons emitted from the surface for10 - 20 days at RT. After exposure, development and fixation of the emulsion made with an ordinary photographic technique deposited Ag particles on the specimen surface, corresponding to abundance of tritium within a few ?m, i.e. the penetration depth of the tritium ? electrons, from the surface. Deposited particles were examined using a scanning electron microscope equipped with energy-dispersive X-ray analysis (SEM-EDX). Ag precipitates were successfully observed around grain boundaries and pores on the specimen surface. Under the present experimental condition, however, the number of Ag precipitates on the specimen surface was not enough to conclude that tritium (hydrogen) localized around grain boundaries and pores. Further experiments are being performed under different conditions, optimizing the amount of loaded tritium and the term for exposure. Including such data, the detailed hydrogen distribution in the specimen will be discussed.

AFTERNOON BREAK 3:30 PM - 4:00 PM

4:00 PM *I2-S4.1 (invited)
Development of Photocatalysts for Solar Hydrogen Production. (#1264) Akihiko Kudo, Department of Applied Chemistry, Tokyo University of Science, Tokyo, Japan.

The importance of hydrogen energy has recently been re-recognized because of the interest in clean energy. Hydrogen is mainly produced by steam reforming of hydrocarbons such as methane in industry. Hydrogen must be produced from water using a renewable energy source, if one considers the energy and environmental issues. Therefore, photocatalytic water splitting is still a challenging reaction because it is an ultimate solution to these serious problems. In the present paper, we introduce various photocatalyst materials aiming at water splitting [1]. Alkali and alkaline earth tantalates have arisen as a new group of photocatalyst materials for water splitting into H₂ and O₂ under ultraviolet light irradiation. Among the tantalates, a NiO (0.2 wt %)/NaTaO₃:La (2%) photocatalyst with a 4.1-eV band gap showed high activity for water splitting into H₂ and O₂ with an apparent quantum yield of 56% at 270 nm. The NiO/NaTaO₃:La photocatalyst have demonstrated highly efficient water splitting using a powdered photocatalyst system. Many visible-light-driven photocatalysts have also been developed through band engineering by doping of metal cations, new valence formation, and by making solid solution. BiVO₄, AgNbO₃, and TiO₂ co-doped with Rh and Sb photocatalysts showed high activities for O₂ evolution in the presence of sacrificial reagent (Ag⁺) under visible light irradiation (wavelength > 420 nm). Pt/SrTiO₃ doped with Rh showed high activity for H₂ evolution from aqueous solutions containing a reducing reagent. Overall water splitting under visible light irradiation has been achieved by construction of a Z-scheme photocatalysis system employing the visible-light-driven photocatalysts, Pt/SrTiO₃:Rh for H₂ evolution and BiVO₄ for O₂ evolution, and an Fe³⁺/ Fe²⁺ redox couple as an electron relay. On the other hand, AgInS₂-CuInS₂-ZnS solid solution photocatalysts showed high activity for H₂ evolution from aqueous solutions including sulfur compounds as electron donors even under simulated solar light irradiation (AM-1.5). [1] A. Kudo, Int. J. Hydrogen Energy, 32, 2673-2678 (2007), Pure Appl. Chem., 79 [11], 1917-1927 (2007).

4:30 PM *I2-S4.2 (invited)
Thermoelectric Properties of Cobalt Oxides Having Pseudo-One-Dimensional Structures. (#1266) Tsuneo Matsui, Kouta Iwasaki; Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan.

Recycling of waste heat is an important issue for the efficient use of energy. Thermoelectric materials are viable candidates for recycling of waste heat since they can directly convert heat into electrical energy. The energy conversion efficiency of thermoelectric materials is evaluated using the figure of merit (Z), defined as Z = σS²κ^-1 (σ is the electrical conductivity, S is the Seebeck coefficient, and κ is the thermal conductivity). σS² is related to electric power for thermoelectric generation and is referred to as the power factor. Oxide ceramics have received attention as thermoelectric materials for power generation since they are relatively stable compared to intermetallic materials at high temperatures. In oxide ceramics, Na_xCoO₂ and (Ca₂CoO_3+δ)_x(CoO₂) (generally referred to as Ca₃Co₄O₉) are known to show high thermoelectric properties. Both compounds have Co-O triangular lattices consisting of edge-sharing CoO₆ octahedra in the unit cells, and the high power factor for Na_xCoO₂ and Co₃Co₄O₉ arises from the Co-O triangular lattices. Considering the fact that the electrical properties are affected by Co3d-O2p hybridization that mainly determines the electronic structure around Fermi level, we can expect that other cobalt oxides would also exhibit high thermoelectric properties. Several cobalt oxides, e.g., Ca₃Co₂O₆, Sr₆Co₅O₁₅, BaCoO₃, etc., have pseudo-one-dimensional structures consisting of Co-O chains and alkaline earth atoms, in which CoO₆ octahedra and CoO₆ triangular prisms share their faces and alkaline earth atoms isolate the Co-O chains. The power factors of Ca₃Co₂O₆ and Sr₆Co₅O_15-δ (δ = 0.7) crystals along the Co-O chains are relatively low because of their low electrical conductivity. In these compounds, the concentration of conductive carrier (hole) tends to increase with increasing valence state of Co ions, leading us to investigate the electrical conductivity of compounds with higher valence state of Co ions. Ba₃Co₂O₆(CO₃)_0.7 is a compound that has a pseudo-one-dimensional structure consisting of Co-O chains and the valence state of +3.7 is higher than those of Ca₃Co₂O₆ (Co³⁺) and Sr₆Co₅O_15-δ (Co^3.4+ for δ = 0.7). The electrical conductivity (670 to 430 S cm^-1 in 300-600 K) along the Co-O chains of Ba₃Co₂O₆(CO₃)_0.7 was larger than those of Ca₃Co₂O₆ and Sr₆Co₅O_15-δ . In addition, the Seebeck coefficient was more than 100 μV K^-1, so that the power factor at 300 K reached 0.9x10^-3 W m^-1 K^-2 which is comparable to that of Ca₃Co₄O₉. These results suggest that the thermoelectric properties of cobalt oxides having Co-O chains can be enhanced by controlling the electronic structures. Therefore, further improvement of the thermoelectric properties can be also anticipated in these cobalt oxides.

5:00 PM I2-S4.3
Photocatalytic Activity of Pt-Deposited TiO₂ Powder. (#930) Yasuro Ikuma, Asuka Gamo, Koichi Niwa, Hiroaki Bessho; Kanagawa Institute of Technology, Atsugi, Japan.

TiO2 is known to be a good photocatalysis when it is exposed to U. V. light. TiO2 has to form an electrochemical cell with other materials to be a very effective photocatalyis. Metals especially Pt is a good material for this purpose. One of the methods to connect these materials is to deposit Pt on TiO2. Since TiO2 has to be exposed to outside, the coverage % of TiO2 by Pt will influence the performance of this electrochemical cell. In this study we investigated the effect of deposition method and Pt concentration on the photocatalytic behavior of TiO2 Degussa P-25 (TiO2) and H2PtCl6 were used as starting materials. TiO2 powder was placed in aqueous solution of H2PtCl6. Then H2PtCl6 was reduced to Pt by several methods. The resultant Pt-TiO2 composite was used to produce H2 from water-alcohol mixture while it was exposed to U. V. light. It is found that there is an optimum coverage of TiO2 by Pt. If the concentration of Pt was small or large, Pt-TiO2 composite did not produce H2. Somewhere in the middle, it worked best as a photocatalysis. It is also found that dispersion of Pt-TiO2 composite in water-alcohol mixture is very important for the effective production of H2.

5:15 PM I2-S4.4
Processing and Characterization of Porous Electrochemical Cells for Flue Gas Purification. (#1379) Zeming He,

Zeming He, Kjeld B?hm Andersen, Li Keel, Frederik Berg Nygaard, Mohan Menon, Kent Kammer Hansen Fuel Cells and Solid State Chemistry Department, Ris? National Laboratory, Technical University of Denmark (DTU), DK-4000 Roskilde, Denmark The use of electrochemical cell to convert NOx into N2 is a novel approach for flue gas treatment. Nitric oxide is reduced at the cathode to nitrogen and oxygen anion. The oxygen anions are transported through the electrolyte and O2 is formed at the anode. In the present work, porous electrode materials lanthanum strontium manganese (LSM)-cerium gadolinium oxide (CGO) were first fabricated via the processes of slurry preparation, tape casting and lamination, and sintering. Graphite and wheat powders were used as pore-formers, respectively, to investigate their effects on shrinkage, porosity, and pore size of the sintered materials. The scanning electronic microscope (SEM) observation revealed different microstructures caused by different pore-formers. The electrochemical cells with the multilayered structure of alternative arrangement of electrode LSM-CGO and electrolyte CGO were then fabricated and characterized using same methodology as that of electrode materials. Finally, the cell performance was optimized using composite pore-formers (combination of graphite and wheat powders) to match the shrinkage of the electrode and the electrolyte and to tailor the required porosity for gas penetration.

I2-S5.1
Electrical Conductivity of Titanium Dioxide. (#1263) T Burg, Tadeusz Bak; Centre for Materials Research in Energy Conversion, The University of New South Wales, Sydney, Australia.

This talk will report electrical properties of polycrystalline titanium dioxide by using the measurements of the electrical conductivity at elevated temperatures (1073 K - 1323 K) in the gas phase of controlled oxygen activity [10 Pa < p(O₂) < 75x10⁴ Pa]. The determined electrical conductivity data exhibit a distinct minimum that is related to the n-p transition. These will be considered in terms of the electrical conductivity components related to electrons, holes and ions. It will be shown that increase of temperature results in a shift of the n-p transition point towards higher values of oxygen activity. The effect of oxygen activity on the electrical conductivity will be considered in terms of TiO₂ defect disorder involving oxygen vacancies, which are compensated by titanium vacancies in both n- and p-type regimes.

I2-S5.2
Visible-Light Photocatalytic Properties of Tin Niobates. (#633) Shin-Tae Bae, In-Sun Cho, Dong Wook Kim, Chin Moo Cho, Kug Sun Hong; Seoul National University, Republic of Korea.

Two types of tin niobate-based photocatalysts, SnNb2O6 and Sn2Nb2O7, were synthesized in submicron powder forms from SnO and Nb2O5 by solid state reactions, and their photocatalytic potential to decompose rhodamine B (Rh B) under visible light irradiation was investigated. SnNb2O6 and Sn2Nb2O7 powders were prepared from respective stoichiometric mixtures of SnO and Nb2O5 by solid state reactions. Crystal structures of synthesized products were identified by X-ray diffraction (XRD). The morphology of the powder was observed using a field-emission scanning electron microscope (FESEM). Specific surface area was measured using a Brunauer-Emmett-Teller (BET) surface area analyzer. Diffuse reflectance spectra were obtained using a UV-Vis-NIR spectrophotometer. In order to measure dielectric properties, an impedance analyzer was used. The photocatalytic activities of the tin niobates powders were evaluated via the degradation of rhodamine B (Rh B) dye in an aqueous solution under visible light irradiation using a tungsten halogen lamp with a UV cut-off filter (> 420 nm), and then the amount of remaining rhodamine B was analyzed using an UV-Vis-NIR spectrophotometer. SnNb2O6 and Sn2Nb2O7 decomposed about 78% and 29% of Rh B, respectively, in 10 h, indicating that the former is an efficient photocatalyst. Such a marked difference of photocatalytic performance of SnNb2O6 and Sn2Nb2O7 may be contributed by the difference of specific surface areas of the two types of the powders which influences the contact area between the photocatalyst particles and organic pollutants. Other sources responsible for the marked difference of the photocatalytic performance is ascribed to the difference of the isoelectric point (IEP) to control the degree of surface adsorption of organic pollutants to the semiconductor particles, dielectric constant to control the diffusion layer of the semiconductor particles, and carrier lifetime to control the rate of charge recombination.

I2-S5.3
Characteristic Observation and analysis of ZnO Doped with Carbon Nanotubes in the dye-Sensitized Solar Cells. (#1134) Mi Chen, Horng Show Koo, Yu Jui Wu, Chang Lin Huang, Ming Fong Tai, Lee Han Chiou; Department of Optoelectronic System Engineering, Minghsin University of Science and Technology, Hsinchu, Taiwan.

The physical characterization and analysis of ZnO doped with carbon nanotubes in the dye-sensitized solar cells were demonstrated. The nanostructured and porous ZnO particles were synthesized by a chemical route and drying treatment. Besides, The self-synthesized carbon nanotubes have been purified by microwave digestion method. The purity of carbon nanotubes greatly affect the cell characteristics of the dye-sensitized solar cells. The paste of the nano-sized ZnO particles doped with various weight ratio of carbon nanotubes were coated on the surface of ITO-coated glass substrate, which is the working electrode in the dye-sensitized solar cells. The various weight ratio of carbon nanotubes in porous ZnO particles will lead to the variation of the cell characterization, energy conversion efficiency and Ish, of the dye-sensitized solar cells. These improvements maybe due to the enhanced adsorption of nano-sized ZnO particles and carbon nanotubes for dye and electrolytic solution in the cells.

I2-S5.4
Nickel Oxide Based Catalyst for Global CO₂ Recycling through Methanation Reaction. (#99) Mohd Hasmizam Razali, Department of Science Chemistry, Faculty of Science and Technology, Universiti Malaysia Terengganu, Malaysia.

The catalytic activity of prepared nickel oxide based catalyst by sol gel method of 60Ni-40Ln (Ln = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Gd3+) has been investigated for methanation of CO2 in the presence of H2 to produce renewable energy of methane, CH4. The results obtained concluded that the 60Ni-40Pr catalyst shows the highest activity, with 100% methanation at very low temperature of, 300oC. The result corresponds to the presence of higher specific surface area of 60Ni-40Pr catalyst. The XRD analysis showed that this catalyst has some degree of amorphous properties and the existence of individual phases of cubic NiO and cubic Pr2O3 in the catalyst system, which most probably acts as active site for CO2 methanation. The complimentary results obtained from SEM showed the presents of homogeneous smaller particle size, which support the good performance of 60Ni-40Pr catalyst towards CO2 methanation.

I2-S5.5
Segregation In Niobium-Doped Titanium Dioxide. (#1204) Leigh R. Sheppard¹, Armand Atanacio², Maria Nowotny¹, Tadeusz Bak¹, Kathryn E Prince², Janusz Nowotny¹; ¹Centre for Materials Research in Energy Conversion, The University of New South Wales, Sydney, Australia ; ²Australian Nuclear Science and Technology Organisation, Australia.

There is a growing awareness that properties of functional materials based on ionic solids of non-stoichiometric composition are strongly influenced, or even controlled, by surface properties, which are entirely different from those of the bulk phase. Therefore, the processing of photo-electrodes with desired properties requires understanding of the local surface properties and the establishment of the relationship between the surface properties and the functional properties. This talk will consider the effect of segregation on surface composition of Nb-doped TiO₂.

I2-S5.7
Immitance Studies of DMF Plasticized Salicyclic Acid Doped PMMA Based Gel Electrolytes. (#68) Ikmar Nizam Isa, Department of Physical Sciences, University Malaysia Terengganu, Malaysia.

A gel electrolyte system prepared by dissolving poly (methyl methacrylate) (PMMA) in ethylene carbonate (EC) and propylene carbonate (PC) doped with salicylic acid and plasticized with dimetyl formamide (DMF) has been prepared. The gel was heated to 70 degree centigrade before it was cast into petry dishes. The gel electrolyte was sandwiched between stainless-steel blocking electrodes and the impedance spectroscopy was measured. The activation energy was obtained from the log &sigma versus 1000/T graph. Loss tangent was calculated at every frequency for all temperature. From the tan & delta versus frequency plot, the relaxation time of the ion was calculated and plotted as ln &tau versus 1000/T. The activation energy value was 0.04 eV (0.12 ± 0.04) eV and the activation energy of relaxation was (0.12 ± 0.07) eV. The similarity between these activation energies imply that the protons 'hop' from one electronegative oxygen site in DMF to another.

I2-S5.8
Electrochromic Properties of WO₃/LiClO₄-PC/CeO₂-TiO₂ Prepared by Sol-Gel Coating. (#1030) Chang-Yeoul Kim, Tae-Young Lim, Yu-Sik Park, Hae Jin Hwang; Korea Institute of Ceramic Engineering and Technology (KICET), Republic of Korea.

Electrochromism is the phenomenon of coloration and bleaching of materials like tungsten oxide by applying electrical potential, which was first discovered by Deb. Electrochromic device is comprised of transparent conducting film, electrochromic layer, electrolyte layer, counter electrode, and transparent conducting film. When electrical potential applied, lithium ion is intercalated into tungsten oxide (transparent, bleach state) to form lithium tungsten oxide (blue, colored state). We prepared tungsten oxide thin film by sol-gel dip coating method on ITO glass, and cerium-titanium oxide was also coated on to ITO glass which plays a role as a lithium ion storage layer at the time of reverse voltage. Electrochromic properties of the device were analyzed by potenitstat/galvanostat (Autolab PGSTAT12). Cyclovolatammetry and chronocoulometry method were applied to evaluate current characteristics with electrical potential variations and charge capacitance change with time at ?3V for 30sec, and in-situ optical transmittance properties were simultaneously characterized by 633nm laser.

I2-S5.9
Interfacial Study of Nanoparticle filled Polyetherimide. (#75) Daniel Qi Tan, Yang Cao, Patricia A Irwin, Kevin Schuman, Colin McTigue; GE Global Research Center, USA.

Dielectric properties are very sensitive to the microstructure and defects in materials. For a certain polymer dielectric matrix, addition of inorganic fillers may improve its dielectric properties such as dielectric constant (k), but introduce complexity and defects as well. Nano-sized ceramic particles have received great attention due to their potential to improving dielectric constant, breakdown strength, voltage endurance, and high quality factor at higher frequencies. Nanoparticles, however, render significant particle agglomeration, high interface fraction, and voids/porosity in polymer matrix. This results in both Maxwell-Wagner polarization and lower voltage withstanding. Solving these issues will result in high-k dielectrics with high dielectric strength and thus miniaturization of devices. We have investigated nanoparticle filled polymers aiming at increasing both dielectric constant and strength. In this work, we are focusing on the contribution of interface fraction of nanoparticles to dielectric properties. Particle agglomeration and related interfacial defects were found to jeopardize the breakdown strength. The particle-matrix interface was successfully probed using dielectric spectroscopy. The results show that dielectric properties could be tuned via interfacial engineering.

I2-S5.11
Physical Characterizations of Lead-free Piezoelectric (1-x)K0.5Na0.5NbO3 - (x/5)NayK3-yLi2Nb5O15 Composite Ceramics. (#584) Byeong-Eog Jun, Saes Byul Kim, Byung Chun Choi, Byung Kee Moon, Jung Hyun Jeong; Pukyong National University, Republic of Korea.

The alkali niobates (K,Na)NbO3 based materials have explored as a candidate for substituting the lead-based dielectric and piezoelectric ceramics. The wider compositions of ANbO3 (A = K, Li and Na) displayed phase coexisting i.e. perovskite (Pe), LiNbO3 (LN) and tetragonal tungsten-bronze (TTB) structures in the compositions of K2O-Li2O-Na2O-Nb2O5. The Pe structures seemed to show the distortions with pseudo-orthorhombic symmetry, while the TTB structure rarely showed the orthorhombic distortions by X-ray diffraction analysis. In this report, the physical properties of (1-x)K0.5Na0.5NbO3 (KNN) - (x/5)NayK3-yLi2Nb5O15 (NKLN) composite ceramics were investigated. The LN phase was not included in the NKLN composite ceramics for the Na content of 0 <= y <= 0.4. Where, it is considered that the NKLN ceramics were the two phase composite of Pe and TTB. We discussed the physical properties of the two phases and the three phase composite ceramics by comparing the temperature and frequency dependent dielectric properties in the temperature range from room temperature to 600 ?C and the frequency range from 0.1 Hz to 1 MHz.

I2-S5.12
Investigation of Photocatalytic Reaction for the Titanium dioxide-Phosphor Composite. (#384) Jung-Sik Kim, Jin-Ho Yoon, Chang-Woo Ham; Department of Materials Science and Engineering, University of Seoul, Republic of Korea.

TiO2 semiconductor photocatalysts have the potential to oxidize a wide range of organic compounds, including chlorinated organic compounds, such as dioxins, into harmless compounds such as CO2 and H2O by irradiation with UV light. The addition or doping of small amounts of noble (Pt, Rd, Ag, Au, etc.) and transition metals (V, Cr, Mn, Fe, Ni, etc.) remarkably enhances the photocatalytic reactivity of TiO2. Also, the coupling of TiO2 with other inorganic oxides such as SiO2, SnO2, WO3, In2O3, (Sr,La)TiO3+x, and ZnFe2O4 can change the photocatalytic efficiency and the energy range of photo-excitation. The present study has been performed on the photocatalytic reaction for the TiO2- coated phosphor composite particles. Nanocrystalline titanium dioxide layers were directly coated on the alkaline earth aluminate phosphor, CaAl2O4:Eu2+,Nd3+ particles by an sol-gel processing method and its photocatalytic reaction was analyzed with the degradation of methylene blue (MB) aqueous solution under UV and visible light irradiations. TiO2-coated phosphor powders showed different photocatalytic mechanism, compared with pure TiO2. At UV-irradiation, TiO2-coated phosphor powders showed slow photocatalytic reactivity in the early stage and fast in the latter, compared with that of pure TiO2. However, at visible light irradiation TiO2-coated phosphor powders showed much faster photocatalytic reactivity under visible irradiation than that of pure TiO2 which is almost negligible. In addition, the characterization of the TiO2-coated phosphor powders was done by X-ray diffractometer (XRD), transmission electron microscope, and energy dispersive spectroscopy (EDS). The mechanism of photocatalytic reactivity for the TiO2- phosphor composite will be discussed in points of energy band structure and phosphorescence.

I2-S5.13
Physical Characterization of composite Electrodes Containing Zinc Oxide and Fullerene for Green Energy Cells. (#1137) Mi Chen, Horng Show Koo, Yao Tsung Wang, Tseng Wei Yuen, Lu Su Chen, Cheng Yung Pin; Department of Optoelectronic System Engineering, Minghsin University of Science and Technology, Hsinchu, Taiwan.

With the mature development of silicon materials shortage in market of Si-based solar energy materials and solar cells, novel energy-related materials have been widely researched and made s commercial mass production, the dye-sensitized solar cells is particularly remarkable. This innovative solar energy materials and solar cells have some advantages of low power consumption, low environmental loading, low cost manufacturing in commercial production and comparable to conversion efficiency. This paper demonstrates the physical properties and analysis of ZnO doped with fullerene in the dye-sensitized solar cells. The nanostructured and porous ZnO particles were synthesized by a nanotechnology approach. Besides, The self-synthesized fullerene have been purified by microwave digestion method. The purity of ZnO highly affect the cell characteristics of the dye-sensitized solar cells. The paste of the micro-sized and nano-sized ZnO particles doped with various weight ratio of fullerene were coated on the surface of ITO-coated glass substrate, which is the working electrode in the dye-sensitized solar cells. The various weight ratio of fullerene in porous ZnO particles will lead to the variation of the cell properties, energy conversion efficiency and Ish, of the dye-sensitized solar cells. These improvements maybe due to the enhanced adsorption of micro-sized and nano-sized ZnO particles and fullerene for dye and electrolytic solution in the cells.

I2-S5.14
Monitoring of Electrochemical Copper Removal in Acid- and Alkali-Based Electrolytes for Electrochemical-Mechanical Polishing Applications. (#652) Yong-Jin Seo, Sung-Woo Park, Sang-Jun Han, Young-Kyun Lee, Woo-Sun Lee; Department of Electrical Engineering, Daebul University, Yeongam County, South Jeolla, Republic of Korea.

Copper damascene structures in the fabrication of multilevel interconnection are processed by chemical mechanical polishing (CMP). Recently, electrochemical-mechanical polishing (ECMP) has been suggested as an alternative to the conventional CMP process. The purpose of our present study is to focus certain fundamental aspects of Cu-ECMP. In this approach, we can selectively probe the voltage-activated (not mechanically induced) processes and examine the relative roles of the concentration and operating voltage used in acid- and alkali-based electrolytes. First, the current-voltage (I-V) curves were employed to evaluate the effect of electrolyte concentration on the electrochemical surface reaction of Cu electrode. From this I-V curve, the electrochemical states of active, passive and trans-passive could be characterized. Second, we fundamentally studied the chemical state and element composition of the Cu surface according to the concentration of the electrolyte and the potential variation using X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis. Finally, in this way, we monitored the oxidation and reduction process of the Cu surface by the repetition of anodic and cathodic potential in various electrolytes. From these monitoring, it was important to understand the electrochemical mechanisms in order to determine the optimal process parameter such as operating voltage, current density, and operating time for the ECMP applications. This work was supported by grant No. (R01-2006-000-11275-0) from the Basic Research Program of the Korea Science & Engineering Foundation.

I2-S5.16
Peroxotungstic Acid Precursor Syntheis and Electrochromic WO₃ Thin Film Synthesis and its Characterization. (#1021) Chang-Yeoul Kim, Tae-Young Lim, Min Lee, Eun-Kyung Kim; Korea Institute of Ceramic Engineering and Technology (KICET), Republic of Korea.

Tungsten oxide (WO3) amorphous thin film is well-known as an electrochromic material which changes its color by applying electrical potential. Electrochromic device is expected to be applied for energy saving smart window and anti-dazzling automobile mirror. The precursor coating solution was synthesized by dissolving W metal in hydrogen peroxide (30%). In this study, we controlled the reaction rate of W metal and hydrogen peroxide to obtain the desirable coating solution. That is, we controlled the amount of water and hydrogen peroxide bound to tungsten oxide. WO3 nH2O2 mH2O was obtained by our experiment, where n is about 0.12-0.2 and m is in the range of 2-10. Electrochromic WO3 thin film was prepared by using tungsten metal solution in hydrogen peroxide as a starting solution and by sol-gel dip coating method. The thermal analysis was conducted by DSC/TG method. DSC/TG analysis and XRD pattern showed that tungsten oxide crystal phase formed at 400oC. In the view of electrochemical property, WO3 thin film which was heat-treated at 200oC was amorphous had better than that of the crystalline phase. Crystallization of tungsten oxide decreases active sites of ion intercalation so that current density decreased with heat-treatment temperature. However, thicker film gives more available sites of ion insertion that thicker film shows larger current density and lower visible light transmission.

I2-S5.17
Characteriztion of Electrodepositied Bi-Te and Bi-Sb-Te Thermoelectric Films and Nanowires. (#321) Kyu Hwan Lee, Kyung Hwan Lee, Dong Ho Kim, Ook Joong Kim; Korea Institute of Materials Science (KIMS), Republic of Korea.

Thermoelectric(TE) refrigeration is attracting increasing attention because it can provide rapid cooling response and handle high heating flux devices such as microprocessors. Mimiaturization and integration capability are the major advanteges of thin film TE devices. It is reasonably expected that thin film TE materials will play an important role in microintegrated TE devices. Several thin film deposition techniques have been developed to deposit TE thin films including evaporation, sputtering, chemical vapor deposition, reactive evaporation and molecular beam epitaxy. Theoretical predictions suggest that great improvement can be achieved by nanoengineering materials. For examples, superlattices of PbTe/Pb1-xEuxTe, PbTe/Te, PbTe/PbSe1-xTex, and Bi2Te3/Sb2Te3 show higher ZT to their counterparts. These experiments affirm the feasibility of introducing quantum confinement effects and bandgap engineering concepts to tune the density of states and mobility of the carriers as a means of significantly enhancing thermoelectric power factor (S2?). Moreover, the nanostructured materials can degrade the thermal conductivity (K) by increasing phonon scattering at the various interfaces and atomic mass discontinuities. Even through greater carrier and phonon confinement are expected in one-dimensional nanowires than in two-dimensional superlattice thin film, a few works were reported because of difficult of fabrication and characterization The electrodeposition is a fast, simple and low cost synthetic method, and a good choice for the fabrication of TE superatticed films and nanowires. In this presentation, we will present the optimum condition of electordeposition and TE properties of n-type Bi-Te and p-type Bi-Sb-Te films and nanowires.

I2-S5.18
Rapid, Atomically Smooth Chemical Mechanical Planarization of GaN/SiC Substrates. (#1205) Rajiv K. Singh¹, A. Arjunan², D. Das², S. Lahiri², D. Singh²; ¹Department of Materials Science and Engineering, University of Florida, Gainesville, USA ; ²Sinmat Inc, USA.

Silicon carbide and gallium nitride possess unique properties that makes for high power, high frequency and high temperature electronic devices. These properties have fueled an intense research effort that had led to development of wafers up to 100 mm in diameter.. For rapid commercialization of the SiC/GaN based technology, defect-free atomically smooth surfaces should be produced uniformly over large area in a rapid manner. As SiC/GaN are relatively chemically inert and hard materials, aggressive polishing methods involving very hard particles (e.g diamond,) have been used to achieve high removal rates, but such methods create a high degree of sub-surface damage and scratches. Although slurries, based on softer particles such as colloidal silica have shown promise with optical surface finish, and extremely slow nature of the process ( polishing rates up to 20 nm/hr) makes it unsuitable for commercial applications. We have developed a novel gentle chemical mechanical planarization (CMP) for planarization of The CMP process is characterized use of soft chemically active particles to induce oxidation of SiC/GaN surfaces under appropriate chemical conditions (pH and oxidizers). Due to the chemical action from soft particles, single atomic steps on polished SiC/GaN surfaces have been formed. We have obtained CMP polishing rates up to 500 nm/hr which is nearly an order of magnitude higher than obtained using current state of the art process. The polished surfaces show atomic terracing in both SiC and GaN making them extremely suitable for fabrication of high performance devices. The talk will present the effect of the processing variables on creation of such surfaces and results obtained from devices fabricated on such surfaces.

I2-S5.20
Synthesis of Pure Anatase Titanium Dioxide for Photoelectrochemical Water Splitting. (#933) Koichi Niwa, Tomomi Yoshioka, Yasuro Ikuma; Kanagawa Institute of Technology, Atsugi, Japan.

Renewable energy will be strongly required within coming several years. One of the most promising candidates for energy conversion system is photoelectrochemical water splitting to produce a clean hydrogen energy by applying titanium dioxide. For a high efficiency energy conversion, the crystal form of titanium dioxide is required to be anatase. In this study, pure anatase titanium dioxide was synthesized by sol-gel process using titanium tetraisoproxide. We found that the small amount of sulfuric acid was necessary to obtain a pure anatase phase. If we applied a small amount of hydrochloric acid instead of sulfuric acid, rutile and brookite phases easily appeared. Higher hydrochloric acid content gives higher content of rutile phase of titanium dioxide. The pure anatase phase titanium dioxide powder has a great potential for water splitting catalyst. We synthesized Pt/pure anatase TiO2 structure and photoelechemical water splitting has been achieved.

I2-S5.22
High Efficiency Thin Film Silicon Solar Cell and Module with Newly Developed Interlayer. (#1313) Kenji Yamamoto, Fontier Materials Research Laboratories, Kaneka Corporation, Osaka, Japan.

The paper discusses the development of a novel enhancement of light trapping scheme for a thin film Si based stacked cell and module, where a newly developed interlayer by plasma CVD is inserted between amorphous and microcrystalline Si thin film. This new interlayer leads both intentional controlling the refractive index of it and nothing shunting issues for fabricating series interconnection of large area module. An initial aperture efficiency of 13.4% has been achieved for 910x455mm2 thin film Si tandem module fabricated in a single chamber process of p-i-n microcrystalline cell, which was independently confirmed by AIST. We also proved by numerical simulation that the effect of the interlayer on light trapping towards the top cell is more enhanced with textured substrate. Namely, the optimum combination between the interlayer with lower refractive index and the optimized feature size of the texture of front TCO enhances the internal light trapping of stacked cell.

I2-S5.23
Highly Efficient Thermoelectric Materials: Interaction of layered nanostructures. (#1476) Daryush Ila¹, Robert Lee Zimmerman², Satilmis Budak², Bangke Cheng², Sadik Guner²; ¹AAMU, USA ; ²Alabama A&M University, USA.

Using the ionizing effects of MeV ions we have produced layered structure of nano-materials in order to produce highly efficient thermoelectric materials taking advantage of interaction among nanolayers of nanoclusters of various material systems. Theoretically, the regimented quantum dot superlattice of any material produces new physical properties such as new electrical band structure, mini-phonon bands, as well as new mechanical and thermal properties. Produced material systems for this study are useful both for electrical generation from heat and/or other forms of radiation as well as cooling critical structures, both enhance the applicability to hybrid systems. The performance of a Thermoelectric Generator (TEG) thin film thermoelectric device is quantified by the dimensionless figure of merit ZT = S2 ?T/ k. To obtain large ZT values, we aim to enhance the electrical conductivity and the thermal insulation and increase the Seebeck Coefficient. For some of the materials selected we doped the nano-layers by keV implantation of selected species followed by MeV bombardment. In other selected materials systems we formed nano-layered structures by co-deposition followed by MeV bombardment to form nanocrystals. The interaction among the nano-structures results in the generation of phonon mini-bands reducing the thermal conductivity, while increasing the electrical conductivity. Several materials systems selected for this investigation some of which operate at temperatures around 300K and others to about 1000K. 1- Research sponsored by the Center for Irradiation of Materials, Alabama A&M University and by the AAMURI Center for Advanced Propulsion Materials under the contract number NAG8-1933 from NASA, and by National Science Foundation under Grant No. EPS-0447675. 2- Patent filed/Patent Pending

11:00 AM I3-S2.1
Stopping Heat Flow: Aperiodic Superlattices for Thermoelectric Energy Conversion. (#1194) Mukul Agrawal, Peter Peumans; Stanford University, California, USA.

Periodic phononic bandgap structures have attracted interest because of their ability of stop phonon transport. Periodic Si/Ge superlattices have shown an up to 2-fold reduction in cross-plane thermal conductivity, leading to an almost doubling of the energy conversion efficiency. Practical superlattices contain several hundreds of layers with periodically alternating thickness. The reduction in thermal conductivity originates in part from the reduction of the phonon group velocity near the band edges. Consequently, large benefits of periodic structures are seen at high temperatures. By extending the concept of a phononic bandgap material to aperiodic structures, the phonon propagation characteristics can be molded to a greater extent. Aperiodic one-dimensional structures are used for various application with great success in the optical domain. Here, we present a design methodology to create aperiodic phononic structures that provide an up to 3-fold improved performance over their periodic counterparts in simulations of heat transport. We show that a 26-layer aperiodic Si/Ge superlattice can be designed to achieve a 7-fold reduction in thermal conductivity in the ballistic phonon transport regime. The thickness of each layer ranges from 1-70nm. Ballistic phonon transport is modeled through continuum elastic theory. The temperature-dependent energy distribution of injected phonons, isotropic angular distribution and all polarization branches of phonons have been taken into account. Mode conversion at Si/Ge interfaces is also accounted for. The reason for the higher performance of aperiodic phonon mirrors is the enhanced phonon reflectivity over a broad spectrum of phonon energies, angles of incidence, and all polarizations. The optimization of cross-plane ballistic heat conductivity is a challenging non-convex multi-variable problem. We present a quasi-global optimization scheme that uses the needle optimization technique to hop from one local valley to another deeper local valley and uses Nelder-Mead simplex algorithm to search for the minima in a local valley. Our algorithm results in highly aperiodic mirrors that lower thermal conductivities than their periodic counterparts with far fewer layers.

11:15 AM I3-S2.2
Preparation and Structural Characterization of Thermoelectric Calcium Cobaltite-Based Ceramic Nanofibres via Electrospinning Techniques. (#485) Khairunnadim Ahmad Sekak, Adrian Lowe; Department of Engineering, FEIT, Australian National University, Australia.

Thermoelectrics are materials that have a capacity to convert heat energy into electrical energy through 'seebeck effect' and conversely provide refrigeration capability through 'peltier effect'. Metal oxides, particularly complex layered oxides, receive a great deal of interest as candidate thermoelectric materials since they are nontoxic, thermally stable, have high oxidation resistance, are cheaper, are easier to process and have a wider temperature range. Recently, calcium cobaltite has been identified as a potential thermoelectric material, and its efficiency is believed to be enhanced through structural control on the nanolevel. Electrospinning is a versatile and straight foward techniques to produce one dimensional nanostructure materials. Here, the production of 1-D calcium cobaltite nanofibres through the electrospinning of sol-gels is presented. High quality fibres of consistent diameter are achieved and various techniques have been used to structurally characterize the material. In addition, the effect of composition and calcination temperature on structural morphology has been fully explored, revealing significant variations in phase structure, relative phase amounts and lattice characteristics.

11:30 AM I3-S2.3
Electromechanical Properties and Defect Chemistry of High-Temperature Piezoelectric Materials. (#1023) Holger Fritze, Michal Schulz, Jan Sauerwald, Denny Richter; LaserAnwendungsCentrum, Technical University of Clausthal, Goslar, Germany.

Langasite (La3Ga5SiO15) and gallium phosphate (GaPO4) crystals are shown to exhibit piezoelectrically stimulated bulk acoustic waves up to at least 1400 and 900 ?C, respectively. Therefore, a wide range of high-temperature applications becomes feasible provided that the piezoelectric materials can be operated environmentally independent. Most critical issues are stoichiometry changes due to e.g. low oxygen partial pressures and high losses. Therefore, the paper discusses the atomistic transport and defect chemistry of those crystals and correlates them with the electromechanical properties. First, a one-dimensional physical model is summarized to describe the electromechanical behavior of thickness shear mode resonators at elevated temperatures. The analysis of the resonance spectra showed that the loss of the resonators can be described satisfactorily by mechanical and electrical contributions expressed as effective viscosity and bulk conductivity, respectively. Most remarkably, the mechanical loss in langasite is significantly impacted by the electrical conductivity due to the piezoelectric coupling. That loss contribution shows a maximum at the dielectric relaxation frequency. Minimization of the conductivity or the resonator operation off that frequency is recommended. The effect of the piezoelectric coupling on the loss is negligible for gallium phosphate since it shows an extremely low electrical conductivity. The materials data of the piezoelectric crystals and the resonance characteristics of 5 MHz resonators are presented up to 1050 and 900 ?C for langasite and gallium phosphate, respectively. The mass sensitivity at elevated temperatures is about as high as that of quartz at room temperature. Temperature related frequency fluctuations can be compensated almost entirely by using higher vibration modes. The defect chemistry of langasite is investigated in order to explore the operation limits and options to improve the resonance properties. First, the dominant charge carriers are identified. Undoped langasite shows predominant ionic conduction at elevated temperatures. As long as the atmosphere is nearly hydrogen-free, the transport is governed by oxygen movement. A dominant role of hydrogen is observed in hydrogenous atmospheres since the diffusion coefficient of hydrogen is orders of magnitude higher than that of oxygen. Based on the developed defect model, donors are expected to suppress the oxygen vacancy concentration and, thereby, the loss in langasite. The prediction is proven by niobium doping and found to be valid. Finally, application examples are summarized to demonstrate the capabilities of high-temperature stable piezoelectric materials. For example, the simultaneous determination of mechanical and electrical properties of thin sensor films by resonant sensors enables detection of CO in hydrogen containing atmospheres.

11:45 AM I3-S2.4
Deposition of Thin Films with Large Thermoelectromotive Force Coefficient by Pulsed Laser Ablation. (#653) Sergay Anatolevich Mulenko¹, Anna Paola Caricato², Armando Luches², Francesco Romano², Yuriy Vladymirovich Kudryavtsev¹, Nikolay Tihonovich Gobachuk³; ¹Institute for Metal Physics, National Academy of Sciences of Ukraine (NASU), Kiev, Ukraine ; ²University of Salento, Department of Physics, Lecce, Italy ; ³Kiev State University of Technology and Design, Ukraine.

Semiconducting silicides are potential candidates for practical applications in thermoelectric, photovoltaic devices and for infrared sensors. Thin films were deposited by pulsed laser ablation (PLD) of CrSi2 and beta-FeSi2 targets by using excimer KrF laser with the aim to obtain nanostructures with narrow band gap for thermoelectric converters. The CrSi2-based films exhibit both semiconductor and metal properties, depending on deposition conditions. Thus, the film of 40 nm thick, deposited on Si substrate at 740 K, presents a band gap Eg=0.18 eV, and large thermoelectromotive force (e.m.f.) coefficient S=1.0-1.4 mV/K at 300

12:00 PM I3-S2.5
The Mechanism for Photoelectrochemical Hydrogen Production Using Hematite. (#757) Julie Ann Glasscock¹, Piers R.F. Barnes², Ian Carleton Plumb¹; ¹Australian Commonwealth Scientific and Research Organization (CSIRO) Materials Science and Engineering, Australia ; ²Imperial College London, United Kingdom.

Despite more than 30 years of research into the use of hematite as a photo-electrode for photoelectrochemical hydrogen production, the best efficiencies obtained using this material are still far from the theoretical value expected for a material with its favourable band gap. Low charge carrier mobility and poor interfacial charge transfer kinetics have been suggested as possible reasons for the low efficiencies which have been reported. The role of different dopants is also not clear. In this study, we report on experiments designed to clarify the roles played by different dopants, and to identify the rate-limiting step in the production of hydrogen in these systems.

LUNCH 12:30 PM - 2:00 PM

2:00 PM *I3-S3.1 (invited)
Mechanistic Study of Reduced Proton Transport through ZrO₂ Film on Zr Alloys Brought by Fe Addition. (#1202) Kazuo Kakiuchi¹, Noboru Itagaki¹, Shunichi Suzuki², Takayuki Terai³, Michio Yamawaki³; ¹Nuclear Fuel Industries Ltd, Japan ; ²Tokyo Electric Power Company, Japan ; ³University of Tokyo, Japan.

In order to clarify the mechanism of reduction in hydrogen absorption by Fe-added BWR fuel claddings, surface potentials and photocurrents were measured on the ZrO2 film formed on Zr-based alloys by means of Kelvin probe and photoelectrochemical method, respectively. The surface potential of the oxide film was related to the electrochemical potential gradient over the oxide film which affects the transport of proton through the oxide. The higher concentration of Fe in HiFi alloy compared to the conventional zircaloy 2 alloy brought an increase in the surface potential of the film, which decreased the electrochemical potential gradient, causing the decrease of transport of proton through the film. The result of the photocurrents measurement also supported this estimation.

2:30 PM I3-S3.2
High Efficient Piezoelectric Energy Scavenging using 0.7Pb(Mg2/3Nb1/3)O3-0.3PbTiO3 Single Crystal. (#681) Hyun-Cheol Song, Hyung-Chan Kim, Chong-Yun Kang, Hyun-Jai Kim, Dae-Yong Jeong, Seok-Jin Yoon; Thin Film Materials Research Center, Korea Institute of Science and Technology, Republic of Korea.

Recently, energy harvesting from the environment have been of great interest for self-powering wireless sensor and communication nodes due to limited life time of batteries. In particularly, piezoelectric energy harvesting from ambient vibration sources, which is more ubiquitous than other environment energy, have been attracted and extensively studied. The piezoelectric cantilever has been widely employed to electric generator to convert the mechanical energy into electrical energy efficiently. The performance of cantilever type piezoelectric energy harvester is determined of k31 electro-mechanical coupling coefficients. Rhombohedral relaxor ferroelectric single crystal, which oriented along the <110> direction, shows a larger k31 than <001> direction. From our measurement results, <110> direction has 0.78 of k31 and much larger output power than <001> and ceramics. <110> oriented PMN-PT single crystal could be a high efficient piezoelectric energy harvester and enable to miniaturization of energy scavenger.

2:45 PM I3-S3.3
Biologically Controlled Nucleation and Growth of Nanostructures for Energy Applications. (#1094) David Kisailus, Mandeep Kular, Davil Garcia, James Weaver; Department of Chemical and Environmental Engineering, University of California at Riverside, USA.

In nature, various organisms have evolved specific control mechanisms to regulate the synthesis of a great diversity of inorganic structures that serve a wide range of biological functions. These biomineralizing species use organic templates (e.g., polypeptides, polysaccharides) as scaffolds to build hierarchical inorganic structures with predetermined function. In this work, we use biological molecules found in or adapted from mineralized tissues to control the size, shape and dispersion of inorganic nanostructures (particles and rods) for photovoltaic (TiO2) and gas sensing (ZnO) applications. These molecules control the rates of nucleation and growth processes under mild solution conditions (room-temperature precipitation or hydrothermal syntheses) to guide the resultant nanostructures. Various morphological structures could be formed through control of the chemical interface between organic and inorganic. Control of these inorganic structures have lead to profound impacts on electronic and optical properties, which will be discussed.

AFTERNOON BREAK 3:30 PM - 4:00 PM

4:00 PM *I3-S4.1 (invited)
Materials and Devices for Photovoltaic Electricity Generation and Potential for Climate Change Impact. (#1223) Martin Andrew Green, School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney, Australia.

Most solar cells to date have been based on crystalline silicon wafers, similar to those used in microelectronics. These cells have performed exceptionally well and still show considerable potential for further cost reduction. However, solar cells based on thin-films of photoactive material show more potential to reach to costs required to make a large scale energy impact in the future. Progress in material and devices for such large scale application will be described. Work within the author's group on silicon thin-film photovoltaics and on the use of silicon quantum dots for 'all-silicon tandem' and 'hot carrier' cells will also be described.

4:30 PM *I3-S4.2 (invited)
Photocatalytic Oxide Materials. (#1452) John Stride, The University of New South Wales, Sydney, Australia.

TBA

5:00 PM I3-S4.3
Titanium Dioxide-Based Oxide Materials for Solar Eenergy Conversion. (#1222) Leigh R. Sheppard, Tadeusz Bak, Janusz Nowotny; Centre for Materials Research in Energy Conversion, The University of New South Wales, Sydney, Australia.

The commonly available TiO₂ may be used as a raw material for the processing of a wide range of TiO₂-based materials for environmentally friendly applications. These materials may be applied to harness solar energy for the production of solar-hydrogen by water splitting and water purification as well as for the production of cheap n- and p-type semiconductors. Their processing is based on defect engineering, which allows to impose controlled properties that are desired for specific applications. It is shown that TiO₂ involves a number of lattice species involving both ionic and electronic species in their normal lattice sites and interstitial sites. The properties of TiO₂ may be imposed in a controlled manner by specific combinations of these species. This may be achieved by doping TiO₂ with oxygen and aliovalent ions. A general chemical formula, representing the composition of TiO₂ and its solid solutions, is derived. This formula is reflective of the effect of both thermodynamically reversible defects and extrinsic defects on properties. It is shown that defect chemistry may be used as a framework for the imposition of controlled properties that are desired for specific applications.

5:15 PM I3-S4.4
Titanium Dioxide Modification for Application as the Electrode in the Dye-Sensitised Solar Cell. (#1005) Rachel Anne Caruso, Fuzhi Huang, Yi-Bing Cheng; The University of Melbourne, Parkville, Victoria, Australia.

The efficiency of the dye sensitised solar cell can be enhanced by tailoring the composition, crystal phase and morphology of the titanium dioxide-based electrode. In this study both templating and doping techniques have been combined during the preparation of the titanium dioxide material. The precursor solutions were infiltrated within a porous template, an agarose gel, followed by sol-gel chemistry and a heating step which resulted in the formation of porous inorganic structures. A second metal oxide precursor could be added at various stages during the synthesis. The materials were characterised by electron microscopy to gain an understanding of the morphology, and X-ray diffraction to obtain crystallisation characteristics as a function of the second metal oxide wt. % and heating temperature. It was found that the presence of the second metal oxide could result in higher surface areas with a decrease in the anatase crystal size. The surface properties of the samples were also studied by both nitrogen sorption and monitoring the adsorption of the sensitizing dye, N719. The time at which the second metal oxide was added during synthesis, as well as the type of metal being added, influenced the overall efficiency of the electrode, with some metals improving the open circuit voltage, while in other cases the short circuit current increased.