Specific heat study and Landau analysis of the phase transition in PbTiO₃single crystals

The specific heat of pure lead titanate (PbTiO3) crystals grown by the float-zone method is reported at temperatures of 325–1250 K. The excess specific heat associated with the ferroelectric phase transition was analysed using a 2–4–6 Landau potential to self-consistently determine the Curie–Weiss temperature, the transition points, the total transition enthalpy, as well as the latent heat and entropy discontinuity at the first-order phase change. The temperature ranges over which various excess thermodynamic quantities obeyed the mean-field predictions of the Landau theory were investigated. The coefficients of the Landau potential were also determined, and the results compared to corresponding measurements made on pure polycrystalline lead titanate specimens. The implications of the results with respect to prior discrepancies reported for the first-order character of the phase transition in lead titanate crystals are discussed.