Up-conversion luminescence of rare earth-doped KGd(WO4)2 phosphors for tunable multicolour light generation

Abstract

A series of novel KGd(WO₄)₂ crystalline powders doped with Yb³⁺/Tm³⁺, Yb³⁺/Er³⁺ and Yb³⁺/Ho³⁺ were synthesized using a modified Pechini method. The monoclinic structure of these compounds was confirmed by XRD. The luminescence properties were investigated by measuring up-conversion luminescence spectra and decay curves. KGd(WO₄)₂ crystalline powders doped with Yb³⁺/Tm³⁺, Yb³⁺/Er³⁺ and Yb³⁺/Ho³⁺ exhibit effective multicolour up-conversion luminescence in the VIS and NIR spectral ranges under 980 nm excitation. The vibrational properties of the materials were investigated using μ-Raman spectroscopy. The assistance of low energy phonons of the KGd(WO₄)₂ matrix in the energy transfer processes between the excited manifolds of the Yb³⁺, Er³⁺, Tm³⁺ and/or Ho³⁺ ions during the up-conversion process was discussed. These results indicate that KGd(WO₄)₂ powders doped with selected Tm³⁺, Er³⁺, Ho³⁺ and Yb³⁺ ions may be potentially used as single-component multicolour or white emission phosphors.