Crystal Structure and Ionic Conductivity of La9.5Ge6-xNixO26.25-x Electrolytes of Apatite Structure

• Main Authors: Yu-HsuanLin, 林鈺烜
• Other Authors: Chi-Yuen Huang
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/71960743327093420609

碩士 === 國立成功大學 === 資源工程學系 === 103 === Apatite materials based on lanthanum germanates and doped with nickel (La9.5Ge6−xNixO26.25−x, x = 0, 0.1, 0.15, 0.2, 0.25, 0.5, 0.75, 1) were prepared to synthesize a single phase through solid-state method. XRD patterns indicate that the second phase (LaNiO3) existed when x = 0.25. Accordingly, the limit of solid solubility (x) was approximately 0.25. A single phase could be obtained when the compositional range was 0 ≤ x ≤ 0.25. Crystal structure analysis refined through the Rietveld method distinctly showed that the sample when x = 0 has a hexagonal structure (P63/m). From this result, four possible migration pathways may be established if the interstitial oxygen passes through the largest region in the entire crystal structure. These four pathways are screwlike, three-dimensional routes around the c axis for nickel-doped samples, which have triclinic structure. Because of the complicated structure, migration of interstitial oxygen becomes very difficult. The relationship between the decrease in conductivity and the decrease in interstitial oxygens may be explained by Raman spectroscopy.