Processing and Actuator-properties of PNN-PSN Perovskite Ceramics

Abstract

Relaxor-type ferroelectric perovskites Pb(Ni_<1/3>Nb_<2/3>)O_3-Pb(Sc_<1/2>Nb_<1/2>)O_3(PNN-PSN), though very difficult to obtain in single phase by the usual mixed oxide method, were prepared by a process consisting of heat treatment and then acid treatment of the oxide mixture containing PbO in amount greater than in the perovskite composition. For the crystallization of perovskite phase without the formation of pyrochlore phase and therefore with desirable composition, it was essential that the mole ratio of PbO to the perovskite composition is 2 : 1 or more and the calcination temperature is 950℃ or more. Removing the excess PbO by leaching with a 1N acetic acid solution, then the ceramic sintering was made at 1200-1360℃ in a PbO atmosphere. From the measurement of the dielectric constant against temperature, it was found that the Curie temperature linearly increased from PNN (-150℃) to PSN (100℃). The dielectric constant peak turned from broad to sharp and became higher with increasing PSN content. The actuator function was highly improved by the introduction of PbTiO_3 (PT) into PNN-PSN.