Pressure-induced phase transition in PLZT: a neutron diffraction and dielectric study

Abstract

Zr-rich, La-doped lead zirconate titanate ceramic samples with composition near Pb0.99La0.01(Zr0.91Ti0.09)O3 (hereafter PLZT) were studied by time-of-flight neutron diffraction and dielectric measurements at 295 K and 1 bar and at 250 K versus increasing and decreasing pressure to 0.55 GPa. The diffraction data at 295 K show that the sample has the rhombohedral ferroelectric R3c structure (FR(LT)) and remains in that phase upon cooling to 250 K. As pressure is increased at 250 K, a transition is observed above 0.3 GPa to essentially the antiferroelectric CaTiO3 orthorhombic Pnma (AO) phase. There appear two other peaks in the neutron spectra, suggesting a possible incommensurate cell for this AO. After the initial drop of the FR(LT) content, the transformation remains incomplete to 0.55 GPa with ∼10% of the sample retaining the FR(LT) low pressure phase. On pressure release, 91% of the FR(LT) phase is recovered with the remainder remaining in the AO phase. Isothermal dielectric data at 250 K suggest a structural transition with an onset near 0.37 GPa for increasing pressure, consistent with the diffraction results.