Effect of La-doping content on the dielectric and ferroelectric properties of 0.88Pb(Mg_1/3Nb_2/3)O₃–0.12PbTiO₃ ceramics

Dense relaxor ferroelectric 0.88Pb(Mg_1/3Nb_2/3)O₃–0.12PbTiO₃ (0.88PMN–0.12PT) ceramics with different La-doping contents (0, 1, 2 and 4 at.%) were sintered by using powders synthesized via a solid-state reaction route. The effects of La doping on the microstructures and electric properties of the 0.88PMN–0.12PT ceramics were investigated. It was found that the average grain size, remanent polarization P _r, coercive field E _c, Curie temperature T _c and leakage-current density J of the ferroelectric ceramics decrease significantly with increasing La doping content. The decrease in P _r, E _c and T _c can be understood in term of the fact that the substitution of Pb²⁺ ions by La³⁺ ions suppresses the long-range coupling of BO₆ octahedrons, while the abatement in J can be explained according to the reduction of oxygen vacancies caused by La doping. By fitting the J–E curves, the conduction mechanism of the 0.88PMN–0.12PT ceramics is confirmed to be Ohmic conduction generated from oxygen vacancies. The dielectric and ferroelectric properties of 0.88PMN–0.12PT ceramics are tunable with manipulating the La doping content.