X-ray and optical study of the phase transition in LiCsSO4

Lattice parameters of LiCsSO4 have been measured in the temperature range 160–550 K with an X-ray single-crystal Bond diffractometer. The monoclinic angle γ in the low-temperature ferroelastic phase has been interpreted as an order parameter. Detailed results of X-ray studies of the ferroelastic domain structure supported by observations under a polarizing microscope are presented. An earlier report on the existence of an intermediate phase in LiCsSO4 has not been confirmed.