PHASE-TRANSITION IN THE (LI-0.5-(X 2)K-0.5-(X/2)CS-X)(2) SO4 SYSTEM/

Phase transition in the (Li-0.5-(x/2)K-0.5-(x/2)Cs-x)(2)SO4 system was studied by measuring the specific heat at constant pressure, C-p, as a function of temperature in the temperature range 300-800K. For non-z ero values of X (X = 0.2%, 0.5%, 1% and 2%) the critical behaviour of the phase transition was found to change considerably compared with th at of X = 0 or pure LiKSO4. The observed change in the phase transitio n with increase of Cs2SO4 content (X) was accompanied by a decrease in the thermodynamic parameters: the value of the specific heat at the t ransition point (Delta C-p)(max), the transition temperature, T-1, and the value of the energy of ordering. The results were interpreted wit hin the Landau thermodynamic theory of the phase transition.