| Summary: | 碩士 === 大同大學 === 材料工程研究所 === 88 === In this study, solid electrolytes of stabilized zirconia were prepared via sol-gel method. The influence of starting alkoxides, pH values of precursor solution, and the kind and the concentration of stabilizers on the crystalline structure and the electrical conductivity of the zirconia electrolytes were investigated. It was found that the relative contents of monoclinic phase in the undoped zirconia powders that prepared with starting solution of zirconium n-propoxide were lower than that prepared from zirconium n-butoxide under the same processing condition of H2O/alkoxide molar ratio of 10, the pH of precursor solutions of 8.7 or 12. The tetragonal phase in the sintered samples that had been stabilized by Y2O3 or Yb2O3 was more stable than that in samples stabilized by other stabilizers. The sintered stabilized zirconia that contain 4~8 mol% Y2O3 or Yb2O3 exhibited mixed microstructure of tetragonal and cubic phases, and the relative contents of cubic phase increased with the dopant concentration of stabilizers. It was also found that samples of the sintered Y2O3 or Yb2O3 stabilized zirconia that were prepared from precursors of pH= 5.7 showed higher ionic conductivity and lower activation energy of bulk conduction than the samples that had been prepared from precursor solutions of pH= 8.7 or 10.2. The ionic conductivity at 800~1000℃ of the sintered samples of stabilized zircnoia that contained 4~8 mol% Y2O3 increased with the dopant concentration of Y2O3. In case of samples that were stabilized by Yb2O3, the sample that contained 7 mol% Yb2O3 showed the highest ionic conductivity in the dopant concentration range of 3~8 mol%. And the samples sintered at 1450℃ exhibited higher ionic conductivity at temperatures between 800~1000℃ than that sintered at 1350℃ with same sintering time. And the bulk conductivity of the samples that had been sintered at 1350℃ or 1450℃ with tetragonal/cubic mixed microstructure showed linar relationship with the volume ratio of cubic phase in the sintered body. The activation energies of bulk conductivity of the zirconia samples that contained 3~8 mol% Y2O3 and Yb2O3 and been sintered at 1350℃ or 1450℃ were about 0.91±0.03 eV and 0.84±0.03 eV respectively, and independent of the dopant concentration of stabilizers.
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