Regulation of oxygen vacancy and reduction of lattice thermal conductivity in ZnO ceramic by high temperature and high pressure method

Abstract

Non-toxic and low-cost ZnO ceramic is a promising high-quality thermoelectric material with high Seebeck coefficient, but its high thermal conductivity leads to poor thermoelectric performance. The introduction of point defects is an effective approach to reduce the thermal conductivity of thermoelectric materials. In this study, high temperature and high pressure sintering method was used to regulate the concentration of oxygen vacancies in bulk ZnO crystal. Electron spin resonance showed an increase in concentration of oxygen vacancies with sintering temperature at high pressure. High temperature and high pressure process induced oxygen vacancies coupled with dislocations and micro-nano holes, thereby enhancing the phonon scattering and remarkably reducing the thermal conductivity. In sum, high temperature and high pressure method looks promising for effective regulation of defects and improving the thermoelectric performance of ZnO and other important thermoelectric materials.