Thermal conductivity of perovskite KTaO₃ and PbTiO₃ from first principles

The low thermal conductivity of piezoelectric perovskites is a challenge for high power transducer applications. We report first principles calculations of the thermal conductivity of ferroelectric PbTiO₃ and the cubic nearly ferroelectric perovskite KTaO₃. The calculated thermal conductivity of PbTiO₃ is much lower than that of KTaO₃ in accord with experiment. Analysis of the results shows that the reason for the low thermal conductivity of PbTiO₃ is the presence of low frequency optical phonons associated with the polar modes. These are less dispersive in PbTiO₃, leading to a large three phonon scattering phase space. These differences between the two materials are associated with the A-site driven ferroelectricity of PbTiO₃ in contrast to the B-site driven near ferroelectricity of KTaO₃. The results are discussed in the context of modification of the thermal conductivity of electroactive materials.