Raman characterization studies of synthetic and natural MgAl2O4 crystals

Raman studies are reported for one natural and four synthetic MgAl2O4 spinel crystals and symmetry assignments for the phonon modes of the spinel crystal structure are given. Deviations in the Raman selection rules are observed for the synthetic spinel crystals in the form of additional modes over and above those theoretically predicted. Also, detailed studies of one of the synthetic crystals show a probable disordering in the Mg–Al sites. Raman linewidths and violations of selection rules, as reported here, can aid in the characterization and quality control of synthetically grown crystals.