Heat capacity anomaly due to the α-to-β structural phase transition in ZrW2O8

Heat capacity of ZrW2O8 has been measured as a function of temperature from 340 to 550 K. An anomaly in heat capacity corresponding to the α-to-β structural phase transition was clearly detected for the first time around 431 K. The transition temperature was determined to be 431±1 K, and the minimum bound of the transition entropy as 2.1 J K−1 mol−1. Although this value is smaller than the theoretical one of R ln 2 (=5.8 J K−1 mol−1), the phase transition is considered to be of the order–disorder type.