Processing and properties of relaxor-type ferroelectric Pb(Ni _1/3Nb_2/3)O₃-Pb(Sc_1/2Nb _1/2)O₃ perovskite ceramics

Relaxor-type ferroelectric provskite PNN-PSN solid solutions were prepared by a process consisting of heat treatment of oxide mixture to which PbO is added in excess amount than in the perovskite composition and then acetic acid treatment to remove the excess PbO. The dielectric measurements of the ceramics revealed that the Curie temperature (Tc) shifted toward higher temperature side with an additivity from PNN (-150°C) to PSN (100°C), the dielectric constant at Tc gradually increased from 6000 (PNN) to 30000 (PSN), and the dielectric constant peak turned from broad to sharp indicating a weakening of relaxor behavior, with increasing PSN content. The electric field-induced strain was piezoelectric in the PSN-richer side, while electrostrictive in the PNN-richer side, in mode. The longitudinal field-induced strain, though less than 1×10^-3 at 1500V/mm in the PNN-PSN ceramics, was highly improved by the addition of PT. (PNN: Pb(Ni_1/3Nb_2/3)O ₃, PSN: Pb(Sc_1/2Nb_1/2)O₃; PT: PbTiO₃).