Nanocrystals of Co 2+ ‐Doped MgGa 2 O 4 : Preparation by a Low‐Temperature Combustion Method and Optical Properties

Co 2+ ‐doped MgGa 2 O 4 nanocrystals were prepared at 500°C by a low‐temperature combustion method without any further calcination. Powder X‐ray diffraction (XRD) indicated that the only crystalline phase in the product was MgGa 2 O 4 with a grain size of 33–36 nm. Scanning electron microscopy (SEM) showed that the products contained pores formed by the gases evolved during the combustion reaction. The excitation and emission spectra of the nanocrystalline powders in the visible and near infrared regions were characteristic of tetrahedral Co 2+ ions, suggesting that Co 2+ ions replaced tetrahedral Mg 2+ ions in the MgGa 2 O 4 crystals. We assigned the visible and near infrared luminescent bands to the spin‐allowed 4 T 1 ( 4 P ) → and 4 A 2 ( 4 F ) and 4 T 1 ( 4 P ) → 4 T 2 ( 4 F ) transitions.