Microwave-induced plasma heating and synthesis: In situ temperature measurement of metal oxides and reactions to form ternary oxides

Direct microwave synthesis between solids is limited by the restricted number of materials that exhibit microwave heating at room temperature. The dielectric properties of most materials dictate that microwave heating can occur at higher temperatures, primarily due to increasing conduction losses. Microwave-induced plasma promoted microwave heating circumvents the requirement for room temperature microwave heating allowing microwave methods to be applied to a greater range of materials. For example, MgO heats to >1700 °C using an O 2 plasma and 900 W magnetron power. Here we demonstrate that in situ temperature measurements can be used to identify binary oxides that exhibit significant plasma promoted heating. Furthermore, reactions to form ternary oxides can be monitored to determine if reactions are driven by the dielectric properties of the precursor(s) or product. Reactions between metal oxides can occur within minutes using microwave-induced plasma promoted heating. In situ temperature measurements of precursors and mixtures show that reactions can be precursor or product driven and in some cases self limiting.