Study on electrical conductivity and oxygen migration of the oxide-ion conductors Na$_{0.5}$Bi$_{0.5}$Ti$_{1−x}$Mg$_{x}$O$_{3−x}$

[摘要] Electrical performance and oxygen relaxation behaviour in Na$_{0.5}$Bi$_{0.5}$Ti$_{1−x}$Mg$_x$O$_{3−x}$ compounds were investigated. The oxide ion conductivity of Na$_{0.5}$Bi$_{0.5}$Ti$_{1−x}$Mg$_x$O$_{3−x}$ compounds increased first and then decreased with increasing Mg-doped content. The highest oxide ion conductivity of $4.7\times 10^{−3}$ S cm$^{−1}$ at 773 K was observed for the Na$_{0.5}$Bi$_{0.5}$Ti$_{0.96}$Mg$_{0.04}$O$_{2.96}$compound. A typical relaxation peak in the Na$_{0.5}$Bi$_{0.5}$Ti$_{1−x}$Mg$_x$O$_{3−x}$ sampleswas observed. The activation energy and pre-exponential factors were determined as (1.0 eV, $4.7\times 10^{−16}$ s) and($0.94−1.0$ eV, $6.8 \times 10^{−14}$−3.1 \times 10^{−13}$ s) from internal friction and dielectric relaxation measurement, respectively. The lower oxide ion conductivity in Na$_{0.5}$Bi$_{0.5}$Ti$_{1−x}$Mg$_x$O$_{3−x}$ ($x = 0.06$, 0.08, 0.10) compounds may arise from the lower vacancy mobility. Judging from the electrical performance and relaxation parameters, although lower-level Mg doping can improve oxide ionic conductor, oxygen vacancy mobility in Na$_{0.5}$Bi$_{0.5}$Ti$_{1−x}$Mg$_x$O$_{3−x}$ compounds cannot be improved with increasing Mg-doping content. These results will be meaningful to ameliorate the electrical properties ofNa$_{0.5}$Bi$_{0.5}$Ti$_{1−x}$Mg$_x$O$_{3−x}$ compounds and understand the relationship between the electrical properties and structure.

[学科分类] 材料工程

[关键词] Dielectric relaxation;internal friction;oxide ionic conductivity;enhanced factors;oxygen vacancy mobility.