Thermal and radiative properties of BaZrO3 and Gd2Zr2O7 for thermal barrier coating applications: A first-principles study

BaZrO 3 and Gd 2 Zr 2 O 7 are promising thermal barrier coating materials owing to their high-temperature stability and low thermal conductivity. In this work, the temperature-dependent thermal conductivity of BaZrO 3 and Gd 2 Zr 2 O 7 is investigated from first-principles by combining lattice and radiative heat-transport mechanisms. The lattice thermal conductivity is evaluated by accounting for both particle-like and coherent phonon transport, with the particle-like contribution calculated using temperature-dependent interatomic force constants and including both three- and four-phonon scattering processes, and the coherent contribution evaluated using the Wigner transport formalism. The radiative contribution is evaluated from temperature-dependent optical properties within the Rosseland approximation. Inclusion of four-phonon scattering significantly reduces the particle-like lattice thermal conductivity, while the coherent contribution increases with temperature and becomes comparable to the particle-like contribution in Gd 2 Zr 2 O 7 at elevated temperatures. Radiative heat transport also becomes increasingly significant at high temperatures, contributing substantially to the overall thermal conductivity. The combined particle-like, coherent and radiative transport framework provides a more accurate description of the experimentally observed high-temperature behavior than phonon-only calculations, highlighting the importance of multiple heat-transport channels in these oxide ceramics.