The structural and warm light emission properties of Sm3+/Tb3+ doubly doped strontium bismuth borosilicate glasses for LED applications.

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Strontium Bismuth Borosilicate (SrBiBS as N) glasses doped with Tb3+ ions (N: Tb) and co-doped with Sm3+/Tb3+ (N: SmTb) were synthesized through the process of classical melt quenching. The structural and optical properties are investigated through energy dispersive spectroscopy; X-ray diffraction, Differential thermal analysis (DTA) and Fourier transform infrared spectra (FTIR), Optical absorption (OA) and photoluminescence (PL) spectral studies. X-ray diffraction indicates amorphous nature of glass. DTA curves explained the thermal stability and stress parameters of glasses. FTIR spectrum indicates existing vibrations of borate and silicate units. The absorption spectra have shown nine absorption bands of Tb3+ ions in the visible and NIR regions, due to transitions from ground state 7F6. In visible region, absorption spectra of co-doped glasses exhibited two bands of Tb3+ and three bands of Sm3+ with hyper sensitive transitions at 375 nm (7F6 → 5G6) and 401 nm (6H5/2 → 6P3/2). Photo Luminescence (PL) spectra of N: Tb and N: SmTb glasses is recorded at 375 nm excitation. N: Tb glasses have shown green emission corresponding to 5D4 → 7F5 transition. In all N: SmTb glasses, addition of Tb3+ ions has enhanced Sm3+ emission which is connected to quenching of Tb3+ emission. Moreover, 0.8 mol% of Tb3+ ions in co-doped glass (N: SmTb8) has shown maximum emission. The energy transfer process was inferred from shortening of decay times observed in N: SmTb glasses. The decay profiles fitted with Inokuti-Hirayama model suggests that the electric dipole-dipole interaction(S = 6) between Sm3+ and Tb3+ might dominate in energy transfer mechanism with probability PET and energy transfer parameter Q of 113-173 S-1 and 9.9-12.0 respectively. The color chromaticity (CIE) coordinates from PL emission of N: Tb & N: SmTb glasses have covered Green, Orange red and yellow (warm-light) regions with coordinates in ranges of x = 0.39-0.62 and y = 0.34-0.56.The color temperatures in range of 1713 K-4258 K.