Fig. 1. (a) XRD patterns of GdAlO₃:x%Cr³⁺ (x=0.2, 0.6, 1.0, 1.5, 2.0) powders; (b) A cell of GdAlO₃; (c) SEM picture of GdAlO₃:1%Cr³⁺ powders

Fig. 2. Excitation spectra (λ_em=725 nm) of GdAlO₃:x%Cr³⁺(x=0.2, 0.6, 1.0, 1.5, 2.0) powders

Fig. 3. (a) Emission spectra and (b) normalized emission spectra (λ_ex=583 nm) of GdAlO₃:x%Cr³⁺(x=0.2, 0.6, 1.0, 1.5, 2.0 ) powders

Fig. 4. (a) Tanabe-Sugano diagram showing the relationship between energy levels of Cr³⁺ with 3d³ electron configuration and the related crystal filed parameter, dotted line shows the position of crystal filed parameter in the case of GdAlO₃:Cr³⁺; (b) Configurational coordinate diagram related to the transition processes between the energy levels of Cr³⁺ doped in GdAlO₃:Cr³⁺

Fig. 5. Afterglow decay curves of GdAlO₃:x%Cr³⁺(x=0.6, 1.0, 1.5) with different doping concentrations

Fig. 6. XRD patterns of GdAlO₃:1%Cr³⁺, y%Eu³⁺(y=4, 7, 11, 13, 15, 17) powders with different doping concentrations

Fig. 7. Excitation spectra of (a) GdAlO₃:13%Eu³⁺, (b) GdAlO₃:1%Cr³⁺ and (c)GdAlO₃:1%Cr³⁺, 13%Eu³⁺ powders

Fig. 8. Emission spectra (λ_ex=266 nm) of GdAlO₃:1%Cr³⁺, y%Eu³⁺(y=4, 7, 11, 13, 15, 17) powders with different doping concentrations. The inset shows emission spectrum of GdAlO₃:13%Eu³⁺ powders

Fig. 9. Afterglow decay curves of GdAlO₃:1%Cr³⁺, y%Eu³⁺(y=0, 13) powders. The inset shows the afterglow decay curve of GdAlO₃:13%Eu³⁺powders

Fig. 10. SEM photo of GdAlO₃:1%Cr³⁺, 13%Eu³⁺powders

Fig. 11. The decay curves of GdAlO₃:1%Cr³⁺, y%Eu³⁺ powders

Fig. 12. Luminescence and energy transfer mechanisms of Eu³⁺ and Cr³⁺