Intriguing energy transfer mechanism in oxide and oxy-fluoride phosphate glasses

Phosphate glasses with chemical compositions (mol %) of (66-x) P2O5-17Li(2)O-17Gd(2)O(3)-xEu(2)O(3) and (66-x) P2O5-17Li(2)O-17GdF(3)-xEu(2)O(3) (where x = 0.05, 0.1, 0.5, 1.0 and 2.0) were prepared with conventional melt quenching technique. The physical and luminescence properties of prepared glass samples were investigated systematically. The density and refractive index increase with increasing concentration of Eu2O3. The characteristic intense red emission at 612 nm corresponding to the transition (D-5(0) -> F-7(2)) of Eu3+ ions has been observed for both oxide and oxy-fluoride glass samples. The Judd-Ofelt (J-O) theory is used to evaluate the properties such as oscillator strengths, J-O intensity parameters, radiative transition probabilities, stimulated emission cross section and branching ratios for present glasses. The J-O intensity parameters follow Omega(4) > Omega(2) > Omega(6) trend. The oxyfluoride glasses show longer decay time as compared to oxide glasses. Hence from the properties it is concluded that, the present glass samples can be a good candidate for red light emitting source in solid state lighting applications.