A Study of Structural Phase Transitions in Antiferroelectric PbZrO₃ by Neutron Diffraction

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Temperature dependence of neutron diffraction intensities of PbZrO₃ was measured in the room-temperature antiferroelectric phase. Intensities of strong superlattice reflections with wave vectors q_Σ≡(1⁄4 1⁄4 0) and q_R≡(1⁄2 1⁄2 1⁄2) show different temperature dependence each other. Intensities of weak superlattice reflections with q_P≡(1⁄4 1⁄4 1⁄2)=q_Σ+q_R and products of intensities of reflections with q_Σ and q_R show the same temperature dependence. The crystal structure previously determined by Fujishita et al. [ref. 4] was reexamined; the structure was found to be described by a sum of modulations associated with lattice vibrational modes Σ₃, R₂₅^x and R₂₅^y.
Successive phase transitions concerning these modulations were observed at 233°C and at around 235°C on heating, and at around 235°C and at 228°C on cooling. Because the modulation with q_R is associated with mode R₂₅, another antiferroelectric structural modulation which exists only in the intermediate antiferroelectric phase is required. In fact, an appearance of superlattice reflections with q_M≡(1⁄2 1⁄2 0) was observed only in the intermediate phase.