Low phonon conductivity of layered BiCuOS, BiCuOSe, and BiCuOTe from first principles

Abstract

Combining the effect of layer mixing, mass mismatch, and intrinsic defects, we have investigated the origin of very low phonon conductivity k(p) in thermoelectric (TE) BiCuOQ (Q: S, Se, Te) compounds. Based on the first-principles anharmonic, lattice dynamics calculations, we use the single-mode relaxation time approximation of the linearized phonon Boltzmann equation, which shows good agreement with experiments. Here, we found that the most important parameter for low k(p) is the interlayer interaction between the BiO and CuQ layers. By analyzing the phonon linewidth distribution, which indicates the phonon scattering rate, we propose that the interlayer interactions play a critical role on suppressing k(p), i.e., the heterolayered crystal controls these interlayer interactions, achieving low k(p) and optimal TE properties.