A review on magnesium aluminate (MgAl2O4) spinel: synthesis, processing and applications

Magnesium aluminate (MgAl2O4) spinel (MAS) is a synthetic material with cubic crystal structure and excellent chemical, thermal, dielectric, mechanical and optical properties. These properties made MAS an indispensable material for optically transparent windows, domes and armours, and for certain refractory applications. High processing cost of dense MAS ceramics is in the main responsible for its limited usage in certain important applications despite its excellent performance in them. The volume expansion (similar to 8%) associated with MAS phase formation from alumina and magnesia does not allow obtaining dense MAS bodies in a single-stage reaction sintering process. Therefore, dense MAS bodies are made by following a double stage firing process, which is expensive. The existing literature suggests that the processing cost of dense MAS ceramics could be reduced to a great extent by decisive selection of starting raw materials, powder processing and densification conditions, and by understanding the underlying mechanisms of MAS formation and densification. Since there is no review article covering the complete comprehensive information of MAS, an attempt is made to write this review article with a main perspective of synthesis, processing and important applications of MAS and its utility for certain future emerging novel and innovative applications.