Spectral investigations on Eu 3+ ,Sm 3+ -doped and Sm 3+ /Eu 3+ co-doped potassium-fluoro-phosphate glass emitting intense orange-red for lighting applications

Potassium fluoro-phosphate (KFP) glass singly doped with different concentrations of europium (Eu ) or samarium (Sm ) or co-doped (Sm /Eu ) was prepared, and their luminescence spectra were investigated. The phase composition of the product was verified by X-ray diffraction analysis. Optical transition properties of Eu in the studied potassium phosphate glass were evaluated in the framework of the Judd-Ofelt theory. The radiative transition rates (A ), fluorescence branching ratios (β), stimulated emission cross-sections (σ ) and lifetimes (τ ) for certain transitions or levels were evaluated. Red emission of Eu was exhibited mainly by the D → F transition located at 612 nm. Concentration quenching and energy transfer were observed from fluorescence spectra and decay curves, respectively. It was found that the lifetimes of the D level increased with increase in concentration and then decreased. By co-doping with Sm , energy transfer from Sm to Eu occurred and contributed to the enhancement in emission intensity. Intense orange-red light emission was obtained upon sensitizing with Sm in KFP glass. This approach shows significant promise for use in reddish-orange lighting applications. The optimized properties of the Sm /Eu co-doped potassium phosphate glass might be promising for optical materials.