Effect of stoichiometry on dielectric and field-induced piezoelectric properties of 0.75pb(Ni1/3Nb2/3)O3-0.25PbTiO3 ceramics

The influences of stoichiometry on the dielectric and field-induced piezoelectric properties of 0.75Pb(Ni1/3Nb2/3)O-3-0.25PbTiO(3) are examined. The addition of excess Ni(Ac)(2) was found to restrain the generation of pyrochlore phase and resulted in pure perovskite phase, while the addition of lead titanate can not enhance the yield of the perovskite phase. With increasing excess nickel content, the maximum dielectric constant decreases gradually and the maximum Curie temperature does not shift, This decrease was attributed to the increase in minor phases with lower dielectric constant. The piezoelectric effect induced by a direct current bias field was also investigated. The evaluation showed that the induced electromechanical thickness coupling coefficients measured at room temperature decreased as the content of excess nickel oxide increased.