Specific Heat of Hexagonal Barium Titanate

The specific heat C p of hexagonal barium titanate has been measured over a wide temperature range from 50 K to 300 K. The C p curve shows a typical second-order-type anomaly at T 0 =222.7 K; the transition enthalpy Δ H , transition entropy Δ S and specific heat jump Δ C p at T 0 are estimated to be 2.2×10 2 J/mol, 1.2 J/mol·K and 4.2 J/mol·K, respectively. The data satisfy the Ehrenfest relation. The C p anomaly associated with the ferroelectric phase transition at about 74 K has not been detected. A discussion concerning the critical indices on the phase transition at 222.7K is presented.