Defect and Diffusion Forum Vols. 242-244

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https://doi.org/10.4028/www.scientific.net/DDF.242-244

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Diffusion of Oxygen at Ceramic Interfaces for High-Temperature Solid Oxide Fuel Cells

Authors: Teruhisa Horita, Haruo Kishimoto, Katsuhiko Yamaji, Natsuko Sakai, Yue Ping Xiong, Manuel E. Brito, Harumi Yokokawa

Abstract: Oxygen diffusion was measured at oxygen/cathode/electrolyte interfaces and at oxide scales/alloy interconnects in Solid Oxide Fuel Cells (SOFCs). A stable isotope oxygen exchange technique (16O/18O exchange) was adopted to label the diffusion profiles in the oxides, and secondary ion mass spectrometry (SIMS) depth profiles were examined to determine the diffusion coefficients in the oxide ceramic materials. Diffusivity of oxygen in LaMnO3 cathode was measured under polarized condition (that is, considering the electrochemical process and diffusion). Also, oxygen diffusion in the oxide scales formed on the alloy was measured to clarify the formation mechanism of oxide scale.

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Structural Defect Formation in Inorganic Sol-Gel Derived Oxides

Authors: Elena V. Frolova, Mariya I. Ivanoskaya

Abstract: The advantages and uniqueness of the Inorganic modification of the Sol-Gel method have already been described. Homogeneous nano-composites as well as some exotic glasses, complex-metal-oxides systems with little glass-forming ability, can be produced by this method. Thus, the obtained materials are characterized by a complex structure that leads to the wide variety of physical and chemical properties. Zirconia-containing materials are of utmost interest because of the mechanical toughness and chemical resistance provided by the presence of ZrO2. In the present work, we report on unusual structural peculiarities of the Zr-O, two types of Zr-Ge-O systems (with Zr>Ge and Zr

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High Oxide Ion Conductivity of (Ba_1-x-ySr_xLa_y)InO_2.5+y/2 Members Derived from the Ba₂In₂O₅ System

Authors: Katsuyoshi Kakinuma, Hiroshi Yamamura, Tooru Atake

Abstract: We have discovered a high oxide ion conductor within the perovskite-type (Ba1-x-ySrxLay)InO2.5+y/2 solid-solution system. The system was derived from brownmillerite-type Ba2In2O5, which possessed a ordered oxide ion vacancies. When we doped La3+ into the Ba site, the vacancy changed to a disordered state. The oxide ion conductivity increased with the amount of doped La3+, reaching a maximum value of 0.12 (S/cm) at 800 oC in (Ba0.3Sr0.2La0.5)InO2.75, a level exceeding that of yttria-stabilized zirconia. The oxide ion conductivity of this system was strongly dependent on the unit cell free volume, which appears to be the key parameter governing oxide ion mobility.

159

Germanium in Czochralski Silicon

Authors: De Ren Yang, Jiahe Chen

Abstract: The behaviors of isovalent impurities doped in Czochralski (CZ) silicon crystal have attracted considerable attention in recent years. In this article, a review concerning recent processes in the study about germanium in CZ silicon is presented. The disturbance of silicon crystal lattice in and the influence on the mechanical strength due to germanium doping is described. Oxygen related donors, oxygen precipitation and voids defects in germanium doped Czochralski (GCZ) silicon has been demonstrated in detail. In addition, the denuded zone formation and the internal gettering technology of GCZ silicon is also discussed.

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Cation Transport in Stabilised Zirconias

Authors: Martin Kilo

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Probing the Effects of SHI and Doping-Induced Defects in Nanocrystalline Spinel Ferrites

Authors: Sanjukta Ghosh, Ajay Gupta, V.Raghavendra Reddy, V. Ganesan, Mukul Gupta, Saif Ahmed Khan, S. Kundu, Nitender Kumar

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Size Effect on the Electronic Properties of Doped and Undoped Ceria

Authors: X.-D. Zhou, W. Huebner, H.U. Anderson

Abstract: The roles of grain size and chemical composition on the electronic conductivity (σ) of CeO2 are reported. In undoped high purity (99.995%) CeO2, σ increases with decreasing grain size, indicating generation of low oxidation state Ce species, Ce3+ ions, which act as the electrons. In low purity undoped CeO2, the chemical impurities act as both the acceptor dopants, as well as the components (such as Si) to form amorphous phase in the grain boundaries. In low purity (99.5%) undoped CeO2, size effects are, therefore, influenced by the presence of acceptor dopants and/or blocking grain boundary phases. In low purity undoped CeO2, the grain boundary contribution to the overall resistance decreases with increasing grain size due to dilution effects of the amorphous grain boundary phases. The intentional addition of acceptors (10%) will pin oxygen vacancies over a wide range of oxygen activity. Size effects in acceptor doped CeO2 are mainly related to the presence of grain boundary phases. In Ce0.90Gd0.10O1.95, the grain boundary contribution to total resistance increases with decreasing size, which is due to trapping of oxygen ions.

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