LiK0.9Na0.1SO4 mixed crystals were grown using the slow evaporation method, and their properties were compared with those of pure LiKSO4 crystals. The physical properties and phase transition temperatures of the LiK0.9Na0.1SO4 mixed crystals were obtained by performing Li-7, K-39, and Na-23 nuclear magnetic resonance relaxation and differential scanning calorimetry. Based on the changes in the splitting of the NMR lines and the dependence of the relaxation time on temperature, the molecular motions for each ion in pure LiKSO4 and mixed LiK0.9Na0.1SO4 crystals were different by partial replacing of K ions with Na ions. And, the partial substitution of Na for K changes the phase behavior, and disappears the ferroelastic properties. (C) 2012 Elsevier B.V. All rights reserved.