Atomic Structure of PbZrO₃ Determined by Pulsed Neutron Diffraction

The atomic structure of lead zirconate, PbZrO₃ (PZ), was studied using Rietveld refinement and atomic pair distribution function analysis of pulsed neutron powder diffraction data for the antiferroelectric, intermediate and paraelectric phases. The symmetry of PZ at T = 20 K in the antiferroelectric phase was determined to be Pbam. The structure was characterized by distortions of the ZrO₆ octahedra which are smaller than in previous studies. Locally correlated displacements of Pb in the c direction develop with increasing temperature. The average magnitude was 0.06 Å at room temperature, 0.14 Å at T = 473 K and 0.20 Å in the intermediate phase at T = 508 K. The intermediate phase was characterized by in-plane antiferroelectric Pb displacements which produce {110} superlattice diffraction peaks. Above 473 K the local structure of PZ remains largely unchanged, in spite of the transitions in the long-range order from the antiferroelectric to the intermediate and to the paraelectric phases.

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