Smearing of the reconstructive phase transition in pure and mixed LiK_1-xRb_xSO₄ crystals

The smearing of the reconstructive phase transition in LiK_1-xRb_xSO₄ crystals (x<~0.50), due to the occurrence of different nonuniform local phase transitions, is demonstrated from the temperature dependence of the electrical-conductivity data around the critical region. A model which determines the distribution of critical temperatures is presented and the results are compared with the calorimetric behavior of the system. For the pure compound LiKSO₄, the distribution of critical temperatures is fitted by a Gaussian curve, showing that the smearing of the phase transition is uniquely due to its reconstructive character. The multimodal distribution observed for the mixed compounds suggests the appearance of clusters with different concentrations.