THE POLYMORPHISM PHASE TRANSITION OF LiIO 3 CRYSTAL AND THE RELATIVE STABILITY OF α,β AND ζ-LiIO 3

Abstract

The specific heats of α, β and ξ-LiIO 3 are measured by adiabic scanning calorimeter and fitted in terms of the 5th-order polynomial by the least square method. The entropies, enthalpies and the Gibbs free energies of α, β and ξ-LiIO 3 have been derived. The stabilities at different temperatures have been shown in free-energy curves vs. temperature. The α-phase is a stable phase below 200℃, while the E-phase is a stable one above 300℃. The ξ-phase is stable in a range of 200—300℃. The phase transition mechanism of LiIO 3 and the thermodynamic factor for the existence of complex polymorphism are also discussed from the thermodynamic and structural viewpoints.