Abstract
The longitudinal electromechanical coupling factor (k33) was investigated as a function of PbNi1/3Nb2/3O3– PbTiO3–PbZrO3 (PNN-PT-PZ) piezoelectric ceramic compositions close to the morphotropic phase boundary (MPB). The k33 was influenced by the grain size of PNN-PT-PZ ceramics. The composition of the MPB determined by k33 is slightly different from that of the free permittivity. The maximum value of k33 in PNN-PT-PZ system attained to 0.8 on the composition of 0.5PNN-0.345PT-0.155PZ.