Domain wall motion and precursor dynamics in PbZrO3

Single crystals of PbZrO3 have been studied by dynamic mechanical analysis measurements in the low-frequency range f=0.02-50 Hz. The complex Young's modulus exhibits a quite rich behavior and depends strongly on the direction of the applied dynamic force. In pseudocubic [100]c direction, we found intrinsic elastic behavior as expected from the Landau theory; at the antiferroelectric transition Tc≈510 K, a downwards cusp anomaly in Y′ accompanied by a peak in Y′′ points to a quadratic/linear order parameter/strain coupling in the Landau free energy. Both anomalies are increasing with decreasing frequency showing that the measurements are performed in the limit ωτth>1. Frequency scans around Tc show energy dissipation, which could result from interphase boundary motion and/or heat diffusion. Above Tc, we observe a pronounced precursor softening, quite similar as it was found in other perovskites, which can be perfectly fitted including isotropic order parameter fluctuations. The low-frequency elastic response in [110]c direction is different. Below Tc, we find in addition to the intrinsic anomaly a strong contribution from ferroelastic domains, which leads to an additional softening in Y′. With decreasing temperatures this superelastic softening gradually disappears, due to an increasing relaxation time τDW for domain wall motion, indicating glassy behavior of domain freezing in PbZrO3. In contrast to the [100]c direction, for forces along [110]c, we found a pronounced precursor hardening, starting at about 60 K above Tc. Since this anomaly is of dynamic nature, starting at the same temperature as the observed birefringence and piezoelectric anomalies [Ko et al. Phys. Rev. B 87, 184110 (2013)PRBMDO1098-012110.1103/PhysRevB.87.184110], we conclude that it originates from slow dynamic polar clusters, which freeze at T∗≈550K>Tc.