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, GaZN4‐ZnGa6 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 Zn(Ga1−yAly)2O4:Cr0.013+ (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+.