Phase Transition in Lead Zirconate

Detailed investigations on the dielectric and the thermal properties of PbZrO 3 have been made and compared with those of ferroelectric BaTiO 3 . In contrast with barium titanate, volume change at the transition near 220°C has turned out to be expansion, being δV/V=2.7×10 -3 , and a large amount of anomalous specific heat of ca. 400 cal./mole have been found. Spontaneous polarization estimated from the hysteresis loop, and the effects of D.C. bias upon the permittivity and especially the shift of the transition point all imply that a spontaneous polarization may not exist below the Curie point. Since the dielectric constant, nevertheless, becomes extraordinarily high at the Curie point, it must be reasonable to say that lead zirconate belongs to a new type of dielectrics, say, antiferroelectrics . When the sample contains some additional materials, a narrow region of ferroelectric phase has been observed between antiferroelectric and paraelectric ones. The temperature range of this phase is sensitively affected by the amount and the species of the additional materials.