Effect of La-doping content on the dielectric and ferroelectric properties of 0.88Pb(Mg_(1/3)Nb_(2/3))O_3-0.12PbTiO_3 ceramics

摘要

Dense relaxor ferroelectric 0.88Pb(Mg_(1/3)Nb_(2/3))O_3-0.12PbTiO_3 (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 Pb~(2+) ions by La~(3+) ions suppresses the long-range coupling of BO_6 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.