Influence of red lead on the intensity of green and orange emissions of Sm3+ and Ho3+ co-doped ZnO–SrO–P2O5 glass system

Abstract In this study, we have attempted to amplify green and orange emissions of Sm 3+ and Ho 3+ ions due to co-doping in zinc strontium phosphate glasses by adding different concentrations of red lead. The preliminary structural investigations like EPR and optical absorption spectra of rare earth free glasses have indicated that the lead ions do exist in Pb 3+ state and the covalent character of Pb O bond gradually decreased with increase of Pb 3 O 4 . The optical absorption (OA) spectra of Sm 3+ and Ho 3+ individually doped glasses exhibited conventional bands in the visible and NIR regions. The spectra were characterized using J-O theory. The value of Ω 2 exhibited decreasing trend with increase of Pb 3 O 4 concentration up to 8.0 mol%. The photoluminescence spectra of Sm 3+ , Ho 3+ and co-doped glasses were recorded at an excitation wavelength of 401 nm. The Sm 3+ doped glasses exhibited feeble green and orange emission bands due to 4 G 5/2  →  6 H 52 , 6 H 9/2 transitions in addition to strong 4 G 5/2  →  6 H 7/2 emission at about 600 nm. The visible emission spectra of Ho 3+ doped glasses exhibited green and orange emission bands due to 5 F 4  +  5 S 2  →  5 I 8 and 5 F 5  →  5 I 8 , respectively. These two bands observed to have been overlapped with 4 G 5/2  →  6 H 52 (green) and 4 G 5/2  →  6 H 9/2 (orange) bands of Sm 3+ ions, respectively, in the co-doped glasses. The intensity of green and orange emission lines of co-doped glasses mixed with 8.0 mol% of Pb 3 O 4 seemed to have been intensified nearly two times when compared with that of Sm 3+ individually doped glasses. The increased efficiency of these two emissions is attributed to the decreasing covalent character of glass network due to the increasing concentration of Pb 3 O 4 and the mutual energy transfer between the two co-dopant ions. The emission process is further analyzed using rate kinetic equations and the resultant emission intensities are found to be proportional to the life time of the corresponding excited state.