The proposed experiment is concerned with the rhombohedral ferroelectric (FE) to orthorhombic antiferroelectric (AFE) phase transformation in PZT (lead zirconate titanate) ceramics, which occurs under the influence of an applied compressive stress or hydrostatic pressure. The occurrence of such a transformation has led to applications for these materials in electromechanical energy conversion. The purpose of the investigation is to explore the low temperature (-100 °C to +20 °C) regime, where it is anticipated that the compressive stress required to induce the orthorhombic phase will be reduced on approaching the equilibrium phase transformation temperature. Measurements of the phase fractions and lattice strain during the transformation will be used to assess the role of residual stress. The results of the study will be evaluated using the Clausius-Clapeyron relationship.