Oxide-Ion Conductivity Enhancement of Polycrystalline Lanthanum Silicate Oxyapatite Induced by BaO Doping and Grain Alignment

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• 作者：Koichiro Fukuda ; Ryoji Watanabe ; Masayuki Oyabu ; Ryo Hasegawa ; Toru Asaka ; Hideto Yoshida
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：August 3, 2016
• 年：2016
• 卷：16
• 期：8
• 页码：4519-4525
• 全文大小：498K
• 年卷期：0
• ISSN：1528-7505

文摘

We prepared the c-axis-oriented polycrystal of BaO-doped lanthanum silicate oxyapatite (LSO) by a reactive diffusion technique. The sandwich-type ternary diffusion couple, which was made up of La₂SiO₅/[BaO-doped La₂Si₂O₇ + BaO-doped LSO]/La₂SiO₅, was heated at 1873 K for 100 h. The thin-plate polycrystalline electrolyte was mechanically extracted from the inner part of the annealed couple and characterized by optical microscopy, transmission electron microscopy, electron probe microanalysis (EPMA), X-ray diffractometry (XRD), Raman spectroscopy, and impedance spectroscopy. On the basis of the numbers of cations determined by EPMA and structural data refined by single-crystal XRD, the chemical formula of the constituent crystallites was determined to be (La_9.32Ba_0.28)(Si_5.87□_0.13)O₂₆, where □ denotes a vacancy in the Si site. The combined use of BaO-doping and grain-alignment techniques effectively improved the oxide-ion conductivity, which steadily increased from 2.17 × 10^–2 to 1.42 × 10^–1 S cm^–1 as the temperature increased from 723 to 1023 K. The activation energy of conduction was 0.48 eV.