Luminescence and energy transfer studies on Sm3+/Tb3+codoped telluroborate glasses for WLED applications

Anew series of Sm3+/Tb3+ codoped telluroborate glasses have been prepared by conventional melt quenching technique with the chemical composition (40-x-y)B2O3+15TeO(2)+15Li(2)O+ 15LiF+15NaF-F+xTb(2)O(3)+ySm(2)O(3) (where x = 0, 0.5; y = 0, 0.05, 0.1, 0.25, 0.5, 1 and 2 wt%). The structural and optical behaviour of the prepared glasses were investigated through Fourier transform infrared spectroscopy (FTIR), optical absorption, photoluminescence and lifetime measurements. The fundamental vibrational units of the borate and tellurite network have been identified through FTIR spectra. Nephelauxetic ratio ((beta) over bar) and bonding parameter (delta) values indicate that the Sm-O bonds are ionic in nature. The characteristic emissions of terbium (543 nm, green) and samarium (645 nm, orange-red) were observed while exciting the Tb3+ ions. Higher magnitude of asymmetric intensity ratio (AIR) values confirms the higher asymmetry around the Sm3+ ion site. Decay profiles of Tb3+ ions (D-5(4) state) and Sm3+ ions ((4)G(9/2) state) exhibit double exponential nature. The nature of interaction between the donor (Tb3+) and acceptor (Sm3+) has been analyzed through Inokuti-Hirayama (IH) model. Energy transfer from Tb3+ to Sm3+ ions is dominated by dipole-dipole type interaction. TBLT0.5S glass possess the better colour coordinates (0.41, 0.45) and colour correlated temperature (CCT) value (3524 K) and the same is suggested for eye safe warm white light emitting applications. (C) 2017 Elsevier B.V. All rights reserved.