Magnesium Aluminate Spinel: Structure, Properties, Synthesis and Applications

Magnesium aluminate (MA) is a spinel group of material and rarely available in nature. It exhibits several advantageous thermal, thermo-mechanical, optical, chemical properties which renders it suitable for wide gamut applications starting from refractory to sensor to IR transmitting window. It has face centered cubic structure and has wide solubility to its end members at elevated temperatures. As a result of this solubility, non-stoichiometric compositions exist in the phase field of spinel in the phase diagram. Due to its unavailability in nature, MA spinels are synthetically prepared through different routes and using different starting materials. Among these, solid state reaction sintering or conventional mixed oxide (CMO) method is the most techno-economical viable process. However, the challenge lies with the preparation of dense MA spinel from its oxide precursors in a single stage process is the expansion due to spinellization. Several attempts have been made to overcome this deterring factor through improving the reactivity of the precursors, by controlling the processing parameters, or by using the mineralizers. In this paper crystal structure, stoichiometry in spinel composition, mechanism of spinel formation, different synthesis method, properties and applications are reviewed.