Study in Conduction Mechanism of the Cation Deficient-type Oxide Ion Conductors

当Ta^<5+>离子部分取代Zn_2TiO_4中的Ti^<4+>离子时，在高温下产生阳离子空位，出现氧离子导电。在Zn_（2-x/2）Ti_ Ta_xO_4体系中，在<1-x>反尖晶石型结构的四面体位置上，钽的替代和阳离子空位的形成都发生在四面体位置上。Rietveld分析的基础上的脉冲中子衍射数据进行了假设非常小的安装的氧化物离子材料。在此基础上，推导出了非线性扩散模型，结果表明，在Zn_2Ti_ Ta_xAl_xO_4体系中，正氧离子向四面体位置的正氧离子空位迁移，形成正氧离子空位<1-2x>，正氧离子通过正氧离子空位迁移。由于Ta^&lt;5+&gt;和Al^&lt;3+&gt;^-双取代并没有使氧离子电导增强，因此证实了阳离子空位严格控制氧离子电导。虽然氧化物离子电导率的阳离子空位浓度依赖性显示出低功率，但没有检测到任何明显的阈值，研究结果表明，氧离子迁移的第一步必然是阳离子空位，然后利用新产生的氧离子空位进行氧离子扩散。型Zn_2TiO_4基氧离子导体。

When Ti^<4+> ions in Zn_2TiO_4 were partly substituted by Ta^<5+> ions, cation vacancies were created and oxide ion conduction appears at elevated temperatures. In the present study, oxide ion conduction mechanism, especially on the relationship between the defect structure and oxide ion conduction, were investigated in terms of the structure analyses and electrochemical measurements.In Zn_<2-x/2>Ti_<1-x>Ta_xO_4 system, both tantalum substitution and cation vacancy formation occur at tetrahedral site of the inverse spinel-type structure. Rietveld analyses based on the pulsed neutron diffraction data were carried out assuming very small mount of oxide ion interstitials. As the result, interstitialcy diffusion model were deduced, i.e., the regular oxide ion would shift toward the cation vacancy crated at the tetrahedral site, forming the oxide ion vacancy via which the oxide ion migrate.Zn_2Ti_<1-2x>Ta_xAl_xO_4 system, which possesses no significant cation vacancy, was also prepared. Since the oxide ion conduction enhancement does not appear by means of Ta^<5+> and Al^<3+>^-dual substitution, it was confirmed that the cation vacancy strictly govern the oxide ion conduction. Although cation vacancy concentration dependence of the oxide ion conductivity showed the power low, any obvious threshold was not detected, indicating that the cation vacancy is necessarily for the first step of the oxide ion migration and then oxide ion diffusion is carried out by using the newly created oxide ion vacancy where the displaced oxide ion previously located.The present study revealed the oxide ion diffusion mechanism of the cation-deficient-type Zn_2TiO_4 based oxide ion conductors.