Electronic structure of spinel

The fundamental band gap between conduction and valence bands in aluminate spinels has been found to be at least 8·1 eV; the optical reflectivity peak at this energy possibly represents the lowest-energy exciton. In crystals with non-stoichiometric Al/Mg ratios, the intensity of this first reflection peak appears to decrease with increasing Al/Mg ratio; however, the peak energies themselves are essentially independent of stoichiometry. It seems likely that spinel and olivine in spinel-structure will have electronic transport behavior similar to that of olivine in its normal structure.