Thermal (Kapitza) resistance of interfaces in compositional dependent ZnO-In2O3 superlattices

Compositionally dependent superlattices, In2O3(ZnO)k, form in the ZnO-rich portion of the ZnO-In2O3 phase diagram, decreasing thermal conductivity and altering both the electron conductivity and Seebeck coefficient over a wide range of composition and temperature. With increasing indium concentration, isolated point defects first form in ZnO and then superlattice structures with decreasing interface spacing evolve. By fitting the temperature and indium concentration dependence of the thermal conductivity to the Klemens-Callaway model, incorporating interface scattering and accounting for conductivity anisotropy, the Kapitza resistance due to the superlattice interfaces is found to be 5.0 ± 0.6 × 10−10 m2K/W. This finding suggests that selecting oxides with a compositionally dependent superlattice structure can be a viable approach, unaffected by grain growth, to maintaining low thermal conductivity at high temperatures.