Yb3+ and Er3+ co-doped ZnGa2O4:Cr3+ powder phosphors: Combining green up-conversion emission and red persistent luminescence

ZnGa2O4:Yb3+,Er3+,Cr3+ UCPL powder phosphors were prepared via high temperature solid-state reaction by incorporating a UC pair Yb3+/Er3+ into the PL phosphor ZnGa2O4:Cr3+. Both the PL and UCPL were all achieved in as-prepared ZGO:Yb,Er, Cr powders owing to the energy transfer between Er3+ ions and Cr3+ ions, which is attributed to the spectral overlap between the UC emission band of Er3+ ions and the excitation band of Cr3+ ions. Besides, under the excitation at 980 nm, the ZGO:Yb,Er, Cr powder phosphors can generate strong UC emissions from Er3+ ions at 524 nm, 549 nm, 659 nm and Cr3+ ions around 700 nm. Moreover, the morphological and structural characterization were studied, illustrating all ZGO:Yb,Er, Cr powders are high degree of crystallinity and contain regular long rods with diameter of 600–900 nm. In addition, the influence of the doping content of Yb3+, Er3+, Cr3+ ions and the UCPL mechanism were also discussed in this paper.