Zr-rich, Nb-doped lead zirconate titanate ceramic and powder samples with composition near ${\mathrm{Pb}}_{0.99}{\left({\mathrm{Zr}}_{0.95}{\mathrm{Ti}}_{0.05}\right)}_{0.98}{\mathrm{Nb}}_{0.02}{\mathrm{O}}_3$ [PZT95/5(2Nb)] have been studied in the range of hydrostatic pressure 0–6.2 kbar and temperature 12–295 K by time-of-flight neutron powder diffraction and dielectric measurements. The combination of the two techniques has led to further insights into the properties and pressure-induced ferroelectric rhombohedral $R3c$ $\left(F_{R\left(\mathrm{LT}\right)}\right)$ to antiferroelectric orthorhombic Pbam $\left(A_O\right)$ phase transition in this material, and the diffraction results have provided a detailed view of the ionic displacements induced by changes in pressure and temperature as well as the displacements accompanying the transition. At 295 K the diffraction results revealed a sharp transition at 2.1 kbar; at 200 K this transition occurs at 1.1 kbar. The transformation is incomplete: after the initial sharp drop in the $F_{R\left(\mathrm{LT}\right)}$ content at the transition, 20 wt % of the sample remains in the low-pressure $F_{R\left(\mathrm{LT}\right)}$ phase. Above the transition, the fraction of $F_{R\left(\mathrm{LT}\right)}$, which exists as a minority phase in the high-pressure $A_O$ phase, continues to decrease, but even at our highest pressure of 6.2 kbar, $\sim 8\mathrm{wt}\%$ of the sample remains in the $F_{R\left(\mathrm{LT}\right)}$ phase. The volume contraction at the $F_{R\left(\mathrm{LT}\right)}$-to-$A_O$ transition unexpectedly results in the retained minority $F_{R\left(\mathrm{LT}\right)}$ being anisotropically ”clamped,” with its $a$ axis slightly expanded and $c$ axis contracted at the transition. On pressure release to 1 bar at 295 K, only 26% of the $F_{R\left(\mathrm{LT}\right)}$ phase is recovered, and this remains in the clamped state because of the surrounding majority $A_O$ phase. Heating the sample above 350 K at 1 bar followed by cooling to room temperature results in full recovery of the $F_{R\left(\mathrm{LT}\right)}$ phase. The spontaneous polarization $\left(P_S\right)$ of the $F_{R\left(\mathrm{LT}\right)}$ phase and its pressure and temperature dependences were determined from the ionic displacements. At 295 K, $P_S=38\mu \mathrm{C}∕{\mathrm{cm}}^2$—a value greater than the $31\text{–}32\mu \mathrm{C}∕{\mathrm{cm}}^2$ commonly observed on ceramic PZT95/5(2Nb) samples. The difference is undoubtedly related to residual porosity in ceramic samples as well as the inability of the poling electric field to align all the polar domains. $P_S$ increases monotonically with decreasing temperature, reaching a value of $\sim 44\mu \mathrm{C}∕{\mathrm{cm}}^2$ at 12 K.

• Received 7 February 2005
• Corrected 29 March 2006

DOI:https://doi.org/10.1103/PhysRevB.73.064105