Spectrum designation and effect of Al substitution on the luminescence of Cr3+ doped ZnGa2O4 nano-sized phosphors

Low-temperature photoluminescent spectra of ZnGa2O4:Cr3+ nano-sized phosphors calcined at different temperatures were reported. The fine structure of the emission spectra has been designated to Cr3+ ions in different sites including ideal octahedral, Zn-interstitial, image sites and Ga2O3 impurity. The vibronic sidebands for both Stokes’ and anti-Stokes’ sides are related to the host lattice vibrations, which were confirmed by IR and Raman spectra. Al3+ is substituted in Ga3+ sites to form image (0≤y≤0.5). The blue shift and luminescent intensity variations of the charge transfer band and 3d–3d transitions in the spectra caused by Al substitution were related to larger band gap and stronger crystal field, respectively. The calculated crystal-field parameters indicated that Al incorporation enhanced the crystal field strength and induced more trigonal distortion due to different radii of Al3+ and Ga3+.