Microwave-assisted sintering of a hexagonal perovskite-related protonic ceramic Ba7Nb4MoO20

Proton conduction in the hexagonal perovskite-related oxide Ba7Nb4MoO20 (BNM) holds great potential for high-temperature fuel cells and electrolysis cells, especially at intermediate temperatures below 700°C. However, sintering BNM electrolytes leads to the formation of secondary phases that deteriorate proton-conducting properties. In this study, we propose facile microwave sintering combined with annealing to achieve high purity and structural integrity. We examine the sintering behavior of BNM and the effects of annealing on its density, microstructure, and purity, aiming to optimize the process. We successfully achieve a 98 % relative density in BNM after just 5 minutes of MWS at 1350°C. Furthermore, annealing at 1050°C significantly improves proton conduction in both the bulk and grain boundaries, highlighting the importance of purity when using BNM as an electrolyte. This approach markedly reduces processing time and energy consumption, offering a viable way for fabricating high-density, high-purity BNM ceramics.