Abstract
The low-temperature ferroelectric-paraelectric phase transition occurring in lead scandium tantalate (PbSc12/Ta12/O3) has been investigated by X-ray diffraction. The symmetry of the low-temperature phase is shown to be rhombohedral and the lattice parameters are given over the temperature range 30-300K. The atomic displacements occurring in the rhombohedral phase, and their behaviour with temperature, are described.