Structure and ionic conductivity of well-aligned polycrystalline sodium titanogallate grown by reactive diffusion
Structure and ionic conductivity of well-aligned polycrystalline sodium titanogallate grown by reactive diffusion
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DOI：
10.1016/j.jssc.2015.06.005
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发表时间：
2015-09-01
影响因子：
3.3
通讯作者：
Fukuda, Koichiro
中科院分区：
文献类型：
--
作者：
Hasegawa, Ryo;Okabe, Momoko;Fukuda, Koichiro
采用反应扩散技术在ga2o3掺杂的Na2Ti4O9基体中制备了b轴取向的多晶Na0.8Ti0.51Ga4.37O8 （NTGO）。当夹层型Ga2TiO5/NaGaO2/Ga2TiO5扩散偶联在1323 K下加热24 h时，在液相存在下容易形成NTGO多晶。用x射线衍射、电子显微镜和阻抗谱对制备的多晶材料进行了表征。对退火后的扩散偶进行机械加工，得到了主要由晶粒排列的NTGO多晶组成的薄板电解质。当温度从573 K增加到1073 K时，电解质沿公共b轴方向的离子电导率（sigma）从13 × 10(-4) S/cm稳步增加到7.3 × 10(-3) S/cm。σ的Arrhenius曲线在约792 K处出现斜率变化；在此温度以上活化能为0.39 eV，在此温度以下活化能为0.57 eV。NTGO的晶体结构为C2/m空间群，两个Ga位点中有一个存在明显的位置紊乱。Na+离子占据约43%的Wyckoff位置4i位点，这将导致沿b轴的离子电导率相对较高。反应扩散作为一种新技术，在制备多组分晶粒取向陶瓷中具有广泛的应用前景。(C) 2015爱思唯尔公司版权所有。
We prepared the b-axis-oriented polycrystalline Na0.8Ti0.51Ga4.37O8 (NTGO) embedded in Ga2O3-doped Na2Ti4O9 matrix using the reactive diffusion technique. When the sandwich-type Ga2TiO5/NaGaO2/Ga2TiO5 diffusion couple was heated at 1323 K for 24 h, the NTGO polycrystal was readily formed in the presence of a liquid phase. The resulting polycrystalline material was characterized by X-ray diffractometry, electron microscopy and impedance spectroscopy. We mechanically processed the annealed diffusion couple and obtained the thin-plate electrolyte consisting mostly of the grain-aligned NTGO polycrystal. The ionic conductivity (sigma) of the electrolyte along the common b-axis direction steadily increased from 13 x 10(-4) to 7.3 x 10(-3) S/cm as the temperature increased from 573 to 1073 K. There was a slope change at ca. 792 K for the Arrhenius plot of sigma; the activation energies were 0.39 eV above this temperature and 0.57 eV below it. The NTGO showed the crystal structure (space group C2/m) with substantial positional disordering of one of the two Ga sites. The Na+ ions occupied ca. 43% of the Wyckoff position 4i site, the deficiency of which would contribute to the relatively high ionic conductivity along the b-axis. The reactive diffusion could be widely applicable as the novel technique to the preparation of grain-aligned ceramics of multi-component systems. (C) 2015 Elsevier Inc. All rights reserved.