The transition from dielectric-temperature stability to diffuse phase transition behavior induced by the sintering temperature for (Ba0.93La0.07)(Ti0.93Tb0.07)O3 ceramics
Nominal (Ba0.93La0.07)(Ti0.93Tb0.07)O3 ceramics (BLTT7) were prepared at different sintering temperatures of Ts = 1100-1400 °C using a mixed-oxide method. The electron paramagnetic resonance (EPR) of Tb4+ in BLTT7 acted as a probe to investigate the effect of Ts on the transition from dielectric-temperature stability to diffuse phase transition behavior. Three tetragonal BLTT7 ceramics sintered at Ts = 1100, 1200 and 1300 °C exhibited increasing dielectric-temperature stability, whereas the pseudocubic BLTT7 sintered at Ts = 1400 °C exhibited a diffuse phase transition behavior with higher permittivity and the temperature stability. A so-called core-shell structure should be responsible for the flattening of the Curie peak at Ts ≤ 1300 °C. The higher Ts (=1400 °C) led to a complete incorporation of La/Tb ions in the BaTiO3 lattice and the collapse of the core-shell structure. The transfer of Tb4+ from the shell at Ts ≤ 1300 °C to the perovskite lattice at Ts = 1400 °C was confirmed by EPR. The solid solution formation of BLTT7 sintered at different Ts is discussed.