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 PbTiO${}_3$ and the cubic nearly ferroelectric perovskite KTaO${}_3$. The calculated thermal conductivity of PbTiO${}_3$ is much lower than that of KTaO${}_3$ in accord with experiment. Analysis of the results shows that the reason for the low thermal conductivity of PbTiO${}_3$ is the presence of low frequency optical phonons associated with the polar modes. These are less dispersive in PbTiO${}_3$, leading to a large three phonon scattering phase space. These differences between the two materials are associated with the $A$-site driven ferroelectricity of PbTiO${}_3$ in contrast to the $B$-site driven near ferroelectricity of KTaO${}_3$. The results are discussed in the context of modification of the thermal conductivity of electroactive materials.