Specific Heat of Hexagonal Barium Titanate

Abstract

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 T₀=222.7 K; the transition enthalpy ΔH, transition entropy ΔS and specific heat jump ΔC_p at T₀ are estimated to be 2.2×10² 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 222.7 K is presented.