Spectroscopic studies of Sm3+ ions activated lithium lead alumino borate glasses for visible luminescent device applications

Abstract

Photoluminescence (PL) characterization of Lithium Lead Alumino Borate (LiPbAlB) glasses doped with Sm3+ ions at varying concentrations have been studied by using absorption, excitation, emission, time resolved and confocal image measurements. From the absorption spectra, Judd-Ofelt (J-O) intensity parameters were evaluated and in turn used to estimate various radiative parameters for the fluorescent levels of Sm3+ ion doped LiPbAlB glasses. The PL spectra of Sm3+ ions exhibit three emission bands corresponding to the transitions 4G5/2 → 6H5/2, 6H7/2 and 6H9/2, for which the emission cross-sections and branching ratios were evaluated to know the potentialities of these materials as visible luminescent devices. The decay spectral profiles measured for 4G5/2 → 6H7/2 transition level were used to estimate quantum efficiency of the as-prepared glasses. The non-exponential decay curves observed for higher Sm3+ ion concentrations were well fitted to Inokuti-Hirayama model to understand the predominant energy transfer mechanism involved in the as-prepared glasses. CIE chromaticity coordinates and correlated color temperatures (CCT) were evaluated to understand the utility of the titled glasses in cool white light generation. The confocal images captured under 405 nm CW laser excitation show intense reddish-orange color. From the evaluated radiative parameters, emission cross-sections, quantum efficiency, CIE co-ordinates, CCT temperatures and confocal images, it was observed that LiPbAlB glass with 0.5 mol% Sm3+ ions are more suitable for w-LEDs and reddish-orange luminescent device applications.