Synthesis of (MgCoNiCuZn)O high-entropy oxide composites by microwave heating

(MgCoNiCuZn)O high-entropy oxide (HEO) composites with chemically uniform single rock-salt structure were successfully synthesized thorough a microwave heating process. Heating temperatures were employed at 650–1200 °C with a step of 50 °C for 30 min, respectively. The techniques of XRD, SEM and DTA-TG were used to characterize the composite particles. Heating behaviors were discussed from series recording of input power and reflect power. It was found that (MgCoNiCuZn)O composites can be prepared by microwave heating above 850 °C within 1 h. Under the action of microwave, the rock-salt structure MgO and CoO reacted firstly, while the wurtzite-type ZnO and cuprite-type CuO react last. The mechanism of the reaction sequence are discussed. The DTA-TG curve analysis of the as-synthesized powder points out a complex thermal evolution process. Through the endothermic and exothermic processes, the reaction mechanism of the raw materials under the action of microwave was further explained.