Cr3+ impurity concentration and excitation dependences of magnesium gallate spinel photoluminescent data

Photoluminescent and excitation spectra of MgGa2O4 with 0.1, 0.5, 1.0 and 5.0% Cr3+ were studied at room temperature and 77 K. The samples exhibit broad emission bands in visible and near-infrared regions, associated with octahedral Cr3+ ions. The luminescence integrated intensity increases with concentration between 0.1 and 0.5% Cr3+. For higher concentrations, the luminescence integrated intensity decreases. The 5.0% Cr3+ sample luminescence is almost 50 times weaker than the emission of the 0.5% sample. The luminescence as a function of wavelength excitation and Cr3+ doping level shows different shapes, making evident that there exist several site types for Cr3+ on those samples. From the spectra, the energy transitions were identified. The crystal field Dq and Racah parameter B were obtained with the help of Tanabe–Sugano matrices.