To predict the lattice thermal conductivity κ κ κ latt , we used the single-mode relaxation time approximation (SM-RTA) model. As for the electrical properties, the κ κ κ latt are 3 × 3 tensors, where the diagonal elements correspond to transport along the three Cartesian directions, and we focus mainly on the scalar average (κ xx +κ yy +κ zz )/3, which we denote κ latt . Figure shows the predicted κ latt of the three perovskites as a function of temperature, and values at T = 1000 K are collected in Table .