Weak ferroelectricity in antiferroelectric lead zirconate

Sawyer-Tower polarization (P-E) measurements have revealed dielectric hysteresis loops in antiferroelectric lead zirconate (PZ), suggestive of weak ferroelectric tendencies. Both polarization saturation and reemergence were observed which were on the order of 0.1 and 0.05 {μ}C/cm², respectively. Laser interferometry investigations, then, revealed a strain of approximately 2×{}10^-7 under a field strength of 15 kV/cm. The strain curve has a butterfly shape indicating a contribution from the piezoelectric effect. These results suggest that antiferroelectric PZ may possess a small reversible spontaneous polarization along the c direction, which is consistent with previous structural studies. The weak ferroelectricity is found to disappear in lanthanum-modified lead zirconate, excluding the possibility of defect-induced ferroelectricity in PZ. A competition between zone center (which leads to ferroelectricity) and zone boundary (which leads to antiferroelectricity) transverse phonon modes is discussed with respect to the observed weak ferroelectricity.