Structural and optical properties of ZnGa2_x(YbXCrGe)xO4 (X = Ho and Er) up-conversion photoluminescence materials

ZnGa2_ x(YbXCrGe)xO4 (X = Ho3+, Er3+) compounds are prepared using the solid -state -reaction method. Alteration in the lattice parameters and strain signifies the substitutional doping of elements at the octahedrally coordinated Ga3+ ions. Down -shifting PL properties are observed at the excitation wavelength of 275 nm. NIR wavelength (980 nm) induced up -conversion PL is observed in the Yb and Ho and/or Er doped samples. The prominent green -colored emission is observed in Yb3+ and Ho3+ doped sample and intense red -colored emission is achieved in the Yb3+ and Er3+ doped sample. The existence of up -conversion photoluminescence is mechanistically discussed by considering the energy transfer processes among the Zn2+, Ga3+, Yb3+, Ge3+, Cr3+, Er3+, and Ho3+ ions.