Huge low-temperature polarity in the antiferroelectric PbHfO 3

Another polar phase was discovered in lead hafnate {PbHfO}₃ single crystal below 270 K. The transition was manifested through complex permittivity anomalies with a thermal hysteresis of approximately 30 K. While pristine {PbHfO}₃ crystal was shown to have modest pyroelectric signals of 20–235 nC c{m}^–2 , DC field poling at 10 kV c{m}^–1 induced a huge polarization of 60 µC c{m}^–2 , dramatically larger than values observed in lead zirconate {PbZrO}₃ . The polar nature of this transition was validated through multiple experimental techniques. Similarly to dielectric measurements, the pyroelectric effect showed distinct thermal behavior between cooling and heating cycles. The distinct change in the polarization gap occurring in the polarization–electric field function was observed below the transition. Second harmonic generation measurements have displayed signals sensitive to applied DC fields around the transition point. It was suggested that the mechanism behind this polar transition involves complex interactions within both P{b}²⁺ and {{O}²}⁻ substructures. The possible symmetry of this low-temperature polar phase was considered based on the absence of the piezoelectric coefficients {d}₃₁ and {d}₃₃ .