The Phase Transition in CsCl Mixed with CsBr, RbCl, and KCl

The phase trans tion in single crystals of CsCl mixed with CsBr, RbCl, and KCl was investigated by means of ionic conductivity measurements and differential thermal analysis. Adding RbCl or KCl to CsCl reduces both the transition temperature, Ttr, and the enthalpy of transformation, ΔHtr. In the system CsClCsBr Ttr shifts to higher values relative to that of pure CsCl, whereas ΔHtr decreases considerably. A thermodynamical consideration of the phase transition temperatures in the CsClCsBr system shows that pure CsBr should exhibit a transition from the B2 to the B1 structure at 880 °C with an enthalpy variation of (300 ± 100) cal/mol. From the DTA experiments one should expect an enthalpy of (100 ± 50) cal/mol for the transformation of pure CsBr.