Anisotropy of oxide-ion conduction in apatite-type lanthanum silicate

详细信息	查看全文 | 推荐本文 |

• 作者：Koichiro Fukuda^a ; ^{fukuda.koichiro@nitech.ac.jp} ; Toru Asaka^a ; Masahiro Okino^a ; Abid Berghout^b ; Emilie Bé ; chade^b ; Olivier Masson^b ; Isabelle Julien^b ; Philippe Thomas^b
• 关键词：lanthanum silicate ; oxide-ion conductor ; apatite-type structure ; anisotropy of oxide-ion conduction
• 刊名：Solid State Ionics
• 出版年：2012
• 期刊代码：96_01672738
• 类别：ch
• 出版时间：8 June, 2012
• 卷：217
• 期：Complete
• 页码：40-45
• 文件大小：1146 K

摘要

The anisotropy of oxide-ion conduction was clarified for the apatite-type La_9.33 + 2x(SiO₄)₆O_2 + 3x (0.01 鈮?#xA0;x 鈮?#xA0;0.13). We synthesized the polycrystalline materials of apatite by the isothermal heating of the sandwich-type La₂Si₂O₇/La₂SiO₅/La₂Si₂O₇ diffusion couples at 1873 K for 100 h. The resulting polycrystals were subsequently characterized using optical microscopy, X-ray diffractometry and impedance spectroscopy. The individual c-axes of the crystallites were appreciably aligned along the diffusion direction, while their a-axes were, around the common c-axis direction, oriented randomly. We obtained the impedance spectroscopy data of the polycrystalline electrolyte, the planar electrodes of which were parallel to the common c-axis. Thus, the obtained bulk conductivity (_bulk 鈯?c) corresponds to the average value of those perpendicular to the c-axis, which steadily increased from 1.6 脳 10^鈭?#xA0;5 to 3.8 脳 10^鈭?#xA0;4 S/cm with increasing temperature from 623 to 848 K. The bulk conductivity parallel to the c-axis (蟽_bulk 鈥?c) that was determined in a previous study was, when compared at the same temperature, necessarily higher than the corresponding _bulk 鈯?c value; the magnitude of anisotropy (蟽_bulk 鈥?c / _bulk 鈯?c) steadily decreased with increasing temperature from 2.1 脳 10² at 623 K to 4.5 脳 10¹ at 823 K. The activation energy of _bulk 鈯?c was 0.71 eV, which is almost twice that of 蟽_bulk 鈥?c (0.35 eV).