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

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 (⁶H_5/2 → ⁶P_3/2). 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 P_ET 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.