Development of fast oxide ion conductor and application for new electrochemical devices

本研究对新型快速氧化物离子导电氧化物进行了研究，发现La_2GeO_5、LaOF和Fe重掺杂的LaGaO_3基氧化物的混合氧化物与常规材料相比具有极快的氧化物离子导电性。此外，对LaGaO_3基氧化物的导电机理进行了详细的研究，发现Fe、Co、Ni的掺杂改善了LaGaO_3基氧化物的离子导电性。还观察到部分电子传导。但是，如果Co、Ni或Fe的掺杂量很小，则电子载流子的贡献不大。特别是发现掺杂Fe后，LaGaO_3基氧化物的离子电导率有了很大的提高。在改善氧化物离子导电性的同时，用Fe、Co、Ni掺杂的LaGa3作为电解液，也提高了固体氧化物燃料电池的功率密度。另一方面，La2GeO5基氧化物的晶体结构分析表明，该氧化物具有较大的各向异性离子电导率。La_2GeO_5系统中氧化物离子的高电导率似乎是由于氧化物离子的高迁移率所致。采用激光研磨法制备了纳米级厚度的La2GeO5基氧化物薄膜。结果表明，当La2GeO5基氧化膜的厚度减小到纳米级时，氧化物离子的电导率出现了反常的增加。在纳米厚度的LaGaO_3基氧化膜上沉积La_2GeO_5纳米膜能有效地提高氧化物离子的导电性。

In this study, new fast oxide ion conducting oxide was investigated and it was found that mixed oxide of La_2GeO_5, LaOF, and Fe heavily doped LaGaO_3 based oxide exhibits extremely fast oxide ion conductivity comparing with the conventional materials. Furthermore, conduction mechanisms in LaGaO_3 based oxide was studied in details and it was found that oxide ion conductivity in LaGaO_3 based oxide was improved by doping Fe, Co, and Ni. Partial electronic conduction was also observed. However, if the amount of doped Co, Ni, or Fe is small, the contribution of electronic charge carrier is not significant. In particular, it was found that the oxide ion conductivity in LaGaO_3 based oxide greatly improved by doping Fe. In agreement with the improved oxide ion conductivity, power density of the solid oxide fuel cells is also improved by using Fe, Co, or Ni doped LaGaO_3 for electrolyte. On the other hand, crystal structural analysis of La_2GeO_5 based oxide suggests the large anisotropic oxide ion conductivity is occurred in this oxide. The high oxide ion conductivity in this La_2GeO_5 system seems to result from the high mobility of oxide ion. Making thin film of La_2GeO_5 based oxide with nanometer level thickness was successfully prepared by Laser Abrasion Methods. It was found that the unusual increase in oxide ion conductivity is achieved as the thickness of the La_2GeO_5 based oxide film decreased to a nanometer size. Furthermore, accumulation of La_2GeO_5 nanometer sized film on LaGaO_3 based oxide film with nanometer size thickness is effective for increasing the oxide ion conductivity.