LiGa5-x(YbRCr)(x)O-8 (R = Ho, Er) ceramics were synthesized via the solid-state reaction method. Rietveld fitted X-ray diffraction (XRD) patterns conveyed an increase in the lattice parameters and tensile strain in the co-doped samples. The UV-visible absorption spectra revealed decreased band gap energy and additional near-infrared (NIR) absorption in the Yb co-doped samples. Down-conversion photoluminescence (PL) spectroscopy, with 275 nm excitation, showed strong red emission characteristics. The up-conversion PL, under 980 nm excitation, showed prominent green and red emissions for Yb-3(+)/Ho-3(+) and Yb-3(+)/Er-3(+) co-doping combinations, respectively. The mechanism of up-conversion PL was explained by energy transfer processes among Cr-3(+), Yb-3(+), Er-3(+), and Ho-3(+) ions. Colorimetric analysis showed a red emission in co-doped samples. These results highlight the potential of LiGa5O8-based phosphors for photonic and energy conversion technologies.

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.

Pure and doped (Cr and Ge) ZnGa2O4 compounds are prepared using solid-state reaction method. Single-phase nature of pure and doped ZnGa2O4 compounds is investigated using X-ray diffraction (XRD). XRD results indicate lower theta angle shifting, decrease in particle size and tensile strain in the doped samples. A granular morphology of amalgamated particles is seen in the SEM images. EDS results convey, practically, the same concentrations (atm

Pure and doped (Cr and Ge) ZnGa 2 O 4 compounds are prepared using solid-state reaction method. Single-phase nature of pure and doped ZnGa 2 O 4 compounds is investigated using X-ray diffraction (XRD). XRD results indicate lower theta angle shifting, decrease in particle size and tensile strain in the doped samples. A granular morphology of amalgamated particles is seen in the SEM images. EDS results convey, practically, the same concentrations (atm%) of doped elements as used during the preparation. X-ray absorption near-edge structure (XANES) results helped to determine the valence state of elements. O K-edge XANES shows a significant orbital hybridization of O 2p shells with the d shells of doped atoms (i.e., Cr and Ge). Broad PL bands, of nearly the white-light emission, are observed in all of the samples. Modification in the PL intensity and emitted wavelengths, upon doping of Cr 3+ and Ge 3+ ions, are discussed through the energy transfer mechanisms and defects in the compounds.