Processing and Electromechanical Properties of PNN-PT Ceramics

Abstract

Relaxor-type ferroelectric perovskites, (1-x)Pb(Ni_<1/3>Nb_<2/3>)O_3・xPbTiO_3 with x between 0.32 and 0.4,were prepared through process of heat treatment and then acid treatment of oxide mixtures containing PbO in amount greater than in the perovskite composition. The perovskite phases were crystallized without the formation of pyrochlore phase from the mixtures 5PbO+(1-x)NiO+(1-x)Nb_2O_5+3xTiO_2 at 950℃. By leaching with a 1N acetic acid solution to remove the excess PbO, the perovskite phases were obtained in discrete and cube-shaped particles of 1-5μm size. The ceramic sintering was made at 1180℃ for 3h. Relatively good dielectric and electromechanical properties were observed in the ceramics with x=0.34 to 0.39. The most remarkable was that the ceramic with x=0.36 showed a large longitudinal strain of 0.28% at 1600V/mm near room temperatures.