Analysis of LiKSO4 crystals in the temperature range from 573 to 943 K

The structural phases observed in LiKSO4 crystals due to thermotropic trans itions have been studied for more than a century. Nowadays many different p hases are referenced, but some of the results are still controversial. Stru ctural studies by single-crystal X-ray diffraction from room temperature to 803 K are presented here. Phase II (708 < T < 943 K) is extensively discus sed on the basis of ordered and disordered models, using harmonic and anhar monic atomic displacements, and considering a twinned crystal composed of t hree orthorhombic domains. Analyses of the same phase at different temperat ures determine the best structure model.