Preparation of magnesium and zinc aluminate spinels by microwave heating: Influence of the oxide precursors on the phase composition

This study focuses on understanding the difference between conventional and microwave (MW) heating to obtain magnesium and zinc aluminate spinels (MgAl2O4 and ZnAl2O4) starting from raw oxide powders (magnesia/ alpha-alumina, magnesia/gamma-alumina and zincite/alpha-alumina mixtures). The samples were prepared from these different oxide precursors and submitted to different thermal cycles in a MW multimode cavity. The evolution of phase composition was studied by X-Ray Diffraction (XRD) analysis. The choice of the precursors aimed at studying the influence of the difference of dielectric properties and of the specific surface area on the phase formation under MW. It was shown that spinel phases could be obtained by rapid MW thermal cycles (i.e., 100 degrees C/min under MW vs 25 degrees C/min under conventional heating). The presence of ZnO as a MW absorbent was beneficial for the MW/material interactions. But, for the three considered mixtures, a SiC susceptor was necessary to facilitate heating.

Automated summary

This study compared the effects of conventional and microwave heating on the formation of magnesium and zinc aluminate spinels, finding that spinel phases could be obtained more rapidly under microwave thermal cycles. The presence of ZnO as a microwave absorbent was beneficial for material interactions, but a SiC susceptor was necessary for heating in all considered mixtures.