| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 102 === The purpose of this study was to develop apatite-type lanthanum germanate-based solid electrolytes for SOFC (Solid Oxide Fuel Cell). In order to achieve the best conductivity of the electrolyte materials applications, these ceramics were doped with various ions with different ionic radius from that of Ge4+ ion and to substitute part of the ion Ge4+ in La9.5Ge6O25.25. Research were showing that a wide range of cation content and dopant substitutions are possible, due to the flexibility of the apatite structure in accommodating a range of ion sizes. First, we examined compositions of different cation content. The result indicated that the ceramics with cation-defects were La9.33Ge5.5Nb0.5O26.245 (3.05×10-2 Scm-1), La9.5Ge5.5Mo0.5O26.75 (3.34×10-2 Scm-1)and La9.5Ge5.5W0.5O26.75 (2.95×10-2 Scm-1), which had the best electrical conductivity of those systems at 800 oC. Second, we studied compositions of different dopant substitutions. The results indicated that the ceramics La9.33Ge5.5Nb0.5O26.245 (3.39×10-2 Scm-1), La9.33Ge5.95Mo0.05O26.045 (3.27×10-2 Scm-1) and La9.5Ge5.7W0.3O26.55 (3.20×10-2 Scm-1) had the best electrical conductivity of these systems, respectively. In addition, the La9.5Ge5.7W0.3O26.55 ceramic sintered at 1475 °C which has better electrical conductivity than 8YSZ at operating temperature of 550°C ~800°C.
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