High oxide-ion conductivity in Si-deficient La(Si[])O apatite without interstitial oxygens due to the overbonded channel oxygens

ケイ素欠損型アパタイトLa(Si[]])Oにおける高酸素イオン伝導は余剰酸素原子ではなくオーバーボンド状の酸素原子によって引き起こされる

藤井 孝太郎*; 八島 正知*; 日比野 圭祐*; 白岩 大裕*; 福田 功一郎*; 中山 享*; 石沢 伸夫*; 花島 隆泰*; 大原 高志   

Fujii, Kotaro*; Yashima, Masatomo*; Hibino, Keisuke*; Shiraiwa, Masahiro*; Fukuda, Koichiro*; Nakayama, Susumu*; Ishizawa, Nobuo*; Hanashima, Takayasu*; Ohara, Takashi

Apatite-type rare earth silicates are attractive materials with exhaust application such as solid-oxide fuel cells, due to its extremely high oxide-ion conductivity below 600C. Interstitial (excess) oxygens have been believed to be responsible for the high conductivity in apatite-type materials. On the contrary, the present study clearly reveals the presence of Si vacancies [] in La-rich La(Si[]])O instead of the interstitial oxygens, by single-crystal neutron and X-ray diffraction analyses, density measurements and electronic calculations.