Extremely low thermal conductivity of β−Ga2O3 with porous structure

Due to the ultrawide bandgap (4.9 eV), high carrier mobility (300 cm2V−1s−1), and high thermal stability, β−Ga2O3 can be a potential candidate for high-temperature thermoelectric materials. However, the intrinsically high thermal conductivity may hinder its application for thermoelectric conversion. In this work, porous β−Ga2O3 was prepared by the solvothermal method together with spark plasma sintering technology. Positron lifetime measurement and N2 adsorption confirm the introduction of pores by adding sucrose in the sample preparation. The sucrose-derived β−Ga2O3 sintered at a relatively low temperature of 600 °C remains highly porous, which results in an extremely low thermal conductivity of 0.45 W m−1K−1 at room temperature, and it further decreases to 0.29 W m−1K−1 at 600 °C. This is the lowest thermal conductivity for β−Ga2O3 reported so far. Our work provides an avenue to reduce the thermal conductivity for β−Ga2O3 and is believed to be widely applicable to many other thermoelectric materials.