Defect structure of Ta- and Al- doped Zn_2TiO_4 showing oxide ion conduction via cation vacancy

概要

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To investigate the defect structure of Zn_<2-x/2>Ti_<1_x>Ta_xO_4 and the subsequent oxide ion conduction, equimolar Al^<3+> with Ta^<5+> have been partly substituted instead of Ti^<4+> ions in Zn_2TiO_4, forming Zn_2Ti_<1_2x>Ta_xAl_xO_4 with no significant cation vacancy despite of tantalum substation. Inverse spinel-type structured solid solution was approximately formed up to x = 0.3 and the measured powder density agreed with the nominal model where all the cation sites ware almost occupied. A slight decrease in oxide ion conductivity was observed for Zn_2Ti_<1-2x>Ta_xAl_xO_4 with the dual substitution by x, while apparent increase for Zn_<2-x/2>Th_<1-x>Ta_xO_4, indicating that the cation vacancy is responsible for the oxide ion conduction in Zn_2TiO_4-based system. Powder neutron diffraction revealed the defect structure, which were then discussed in terms of the oxide ion conduction mechanism with the deduced isotropic temperature factors of oxide ions.
社団法人日本セラミックス協会の論文
2008-04-01