Dielectric Properties of Lead Zirconate

In order to distinguish whether it is really a ferroelectric or not, the dielectric response of PbZrO₃ ceramic to biasing dc field has been examined. In contrast to ordinary ferroelectrics, an effect is scarcely detected below the Curie point of 233^∘{}C even up to a field strength of 20 kv/cm, except for a slight increase of permittivity at the vicinity of the transition point. In addition, the Curie temperature decreases with increasing biasing field attaining the value ΔTc=-1.7^∘{}C for 20 kv/cm. The hysteresis loops of this ceramic have been studied. So long as the amplitude of the applied ac field is less than a critical field of about 23 kv/cm, the D-E curves are almost always linear, except that a slight upward curvature becomes perceptible just at the temperature range wherein permittivity increases, and never show any hysteresis characteristics even just below the Curie point. But if the amplitude of the applied field is greater than this threshold value, anomalous hysteresis loops of very impressive form are observed in a narrow temperature range just below the Curie point. These experimental facts all seem to suggest that PbZrO₃ may be, not a ferroelectric, but an antiferroelectric. A preliminary pyroelectric test also seems to show that no net polarization grows spontaneously when the sample is cooled through its Curie point.