Crystal Structure and Electrical Conductivity of Pyrochlore-type  Composition Systems, A2B2O7

Hanako NISHINO; Naoto MATSUNAGA; Katsuyoshi KAKINUMA; Hiroshi YAMAMURA; Katsuhiro NOMURA

doi:10.14852/jcersjsuppl.112.0.S738.0

Journal of the Ceramic Society of Japan, Supplement 112-1, PacRim5 Special Issue

Session ID : 9

DOI https://doi.org/10.14852/jcersjsuppl.112.0.S738.0

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Host: The Ceramic Society of Japan

Co-host: Iketani Science and Technology Foundation, International Ceramic Federation, Commemorative Organization for the Japan World Exposition '70, The American Ceramic Society, The Australasian Ceramic Society, The Chinese Ceramic Society, The Korean Ceramic Society, Joint Research Consortium of Synergy Ceramics/Fine Ceramics Research Association, Nanotechnology Researchers Network Center of Japan, The Special Coordination Funds for Promoting Science and Technology, Japan National Tourist Organization, Aichi Prefectural Government, CASIO SCIENCE PROMOTION FOUNDATION, DAIKO FOUNDATION, Nagoya Convention and Visitors Bureau, The Asahi Glass Foundation, The Kao Foundation For Arts And Sciences, The Murata Science Foundation, The Ogasawara Foundation for the Promotion of Science & Engineering, ASAHI GLASS CO., LTD. Research Center, CENTRAL GLASS CO., LTD., ELECTRIC GLASS INDUSTRY ASSOCIATION OF JAPAN (EGAJ), Hattori Company, Ltd., Hitachi Research Laboratory, Hitachi, Ltd., HOYA CORPORATION, INAX Corporation, ITOCHU CERATECH CORP., Japan Cement Association, KYOCERA Corporation, KYUSHU REFRACTORIES CO., LTD., MINO CERAMIC CO., LTD., Murata Manufacturing Co., Ltd., NGK INSULATORS LTD., NGK SPARK PLUG CO., LTD., NICHIAS Corporation, NIKKO COMPANY, Nippon Electric Glass Co., Ltd., Nippon Sheet Glass Co., Ltd., NORITAKE CO., LIMITED, Tokuyama Corporation, TOTO LTD.

Papers

Crystal Structure and Electrical Conductivity of Pyrochlore-type Composition Systems, A₂B₂O₇

Hanako NISHINO, Naoto MATSUNAGA, Katsuyoshi KAKINUMA, Hiroshi YAMAMURA, Katsuhiro NOMURA

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Keywords: Oxide-ion conductivity, Fluorite-type structure, Pyrochlore-type structure, Rare earth C-type structure, Raman spectra

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Abstract

The relationship between the crystal phase and the electrical conductivity was investigated for the pyrochlore-type composition systems, A₂B₂O₇ (A³⁺=Rare earth element, B⁴⁺=Zr, Ce) and their solid solution systems. The crystal phase of these systems varied among rare-earth C-type, fluorite- and pyrochlore-type phases depending on both the lattice constant and the cationic radius ratio (r_A/r_B), where r_A and r_B denote ionic radii of A- and B-sites in the pyrochlore-type composition, respectively. The lattice constant decreased with increasing the Zr content in the A₂(Zr_1-xCe_x)₂O₇ (A=La, Sm and Yb) systems. Even if the oxygen vacancy concentration was kept constant in all sample systems, the electrical conductivity changed in the wide range. The oxide-ion conductivity increased in proportion to the unit cell free volume in the fluorite-type phases with or without rare-earth C-type superstructure, and decreased sharply in the pyrochlore-type phase range because of the ordering of oxygen vacancy.

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