The proposed experiment involves monitoring the depolarisation behaviour of rhombohedral PZT (lead zirconate titanate) ceramics caused by ferroelectric domain switching during heating up to the Curie point. This will be achieved by measuring the diffraction patterns (in particular the {111} and {200} reflections) during heating and cooling cycles. The influence of an applied compressive stress (25 to 100 MPa) or electric field (0.5 to 1.0 kV/mm) will be evaluated by carrying out experiments within the compressive stress rig on ENGIN-X and by making use of a purpose-built electrically insulated specimen holder. The overall aim of the experiment is to establish the factors that control the stability of the remanent polarisation, with particular reference to the interaction between residual and applied stresses.