The effect of dual substitution of Na and Al on ionic conductivity of Na0.5Bi0.5TiO3 ceramics

The Na and Al dual substitution Na0.5Bi0.5TiO3 samples were synthesized by the conventional solid-state reaction method. The oxygen ion conductivity and migration in the Na0.54Bi0.46Ti1-xAlxO2.96-x/2 (x= 0.02, 0.04, 0.06 and 0.08) samples were investigated. The grain conductivity and relaxation activation energy of the Na0.54Bi0.46Ti1-xAlxO2.96-x/2 samples show the trend of declining-rising-declining with the increase of Al-doped content. The highest grain conductivity can arrive at 0.0016 S/cm for the Na0.54Bi0.46Ti1-xAlxO2.96-x/2 (x= 0.06) sample at 673 K and the corresponding activation energy is about 0.80 eV, which are the lowest results of oxygen ion diffusion in the Na0.54Bi0.46Ti1-xAlxO2.96-x/2 (x= 0.02, 0.04, 0.06 and 0.08) samples. The mobile oxygen vacancy content decreases with increasing Al-doping content in the Na0.54Bi0.46Ti1-xAlxO2.96-x/2 compounds. The sudden change of grain conductivity in NBT-Na4Al6 sample may be from the lower activation energy and better oxygen vacancy mobility. These results are helpful to improve the electrical performance by doping methods.