The specific heat of [N(CH3)4]2ZnBr4 around the ferro-paraelastic phase transition by adiabatic calorimetry

Abstract A calorimetric study of [N(CH 3 ) 4 ] 2 ZnBr 4 is presented. This compound exhibits a second-order phase transition at 287.20 ± 0.12 K from a high-temperature orthorhombic phase (space group Pnma ) to a monoclinic ferroelastic phase (space group P2 1 / a ). Specific heat measurements were carried out by automatic adiabatic calorimetry from 170 to 370 K, and the value obtained for the phase transition entropy was Δ S = 1.95 ± 0.1R (where R is the ideal gas constant). A simple phenomenological model is found to describe the specific heat below T c . The experimental set-up and procedure are also described.