Structural transitions of ß-K2SO4,-type crystals

Abstract Dielectric and spectroscopic investigations have been performed on s-K2SO4-type crystals and the results are compared with respect to the variety of structural transformations observed in these compounds. While many alkaline sulfates and selenates show a high temperature transition to a hexagonal phase only, potassium selenate and ammonium sulfate transform to very different states at low temperature. Additionally a first-order transition of thallium selenate at 70 K is described.