Theoretical investigation of the thermal conductivity of Ga2O3 polymorphs

Gallium oxide (Ga2O3) is a promising thermal preserving and heat-insulating material; understanding the thermal properties is important to improve its performance in technological applications. The thermal conductivities of Ga2O3 polymorphs labeled as alpha, beta , delta , and epsilon are computed via the Boltzmann phonon transport equation (BTE) employing first-principles techniques. The lattice thermal conductivity tensor k of Ga2O3 for temperatures ranging from 50 K to 1000 K is derived using the second and third-order interatomic force constants (IFCs) for the potential based on a generalized gradient approximation (GGA), as well as the phonon dispersion relation, projected density of states (PDOS), and phonon group velocities. The results agree with the observed experimental values of rhombohedral polymorph beta-Ga 2 O 3 and with the previously calculated results of the other phases. At room temperature, the predicted thermal conductivity of the delta-Ga 2 O 3 phase is 15.6 W/(m center dot K). By breaking down k into mode contributions, it is projected that the optical phonons contribute significantly to the lattice thermal conductivity because of a peculiar phonon dispersion relation.