Dielectric, Ferroelectric and Piezoelectric Properties of Pb(In_1/2Nb_1/2)O₃-Pb(Ni_1/3Nb< sub>2/3)O₃-PbTiO₃ Ternary Ceramics Near Morphotropic Phase Boundary

Lead-based complex perovskite ferroelectric materials have been widely used as electromechanical sensors, actuators, and transducers. Among them, Pb(Ni1/3Nb2/3)O-3-PbTiO3 (PNN-PT) based solid solution has been drawn much attentions of scientists for its excellent dielectric and piezoelectric properties near morphotropic phase boundary (MPB) region. However, the relatively high dielectric loss and low Curie temperature near MPB region limited its application in high temperature and high power devices. In this work, Pb(In1/2Nb1/2)O-3 (PIN) was introduced into PNN-PT ceramics for improving their electrical properties and Curie temperature. The ternary ferroelectric ceramics Pb(In1/2Nb1/2)O-3-Pb(Ni1/3Nb2/3)O-3-PbTiO(3 )were successfully prepared by a two-step synthesis process. All samples exhibited pure perovskite phase without any secondary phase. The structure transferred from rhombohedral to tetragonal phase with increasing PT content. The MPB phase diagram of ternary system at room temperature was established based on XRD results. The values of Curie temperature were improved significantly after PIN added into PNN-PT system. Importantly, the introduction of PIN into PNN-PT system can effectively reduce dielectric loss and conductivity. The ceramics in the MPB region exhibited excellent properties. 0.30PIN-0.33PNN-0.37PT ceramic was found to have optimal properties with d(33) =417 pC/N, T-C=200 V , epsilon'= 3206, tan delta=0.033, P-r= 33.5 mu C/cm(2) and E-c=14.1 kV/cm at room temperature, respectively. The Curie temperature and piezoelectric coefficient were improved while dielectric loss and conductivity were reduced after the introduction of PIN into PNN-PT. The enhancements of piezoelectric properties and high Curie temperature make this ternary system a promising material for high power and high temperature transducer applications.