Concentration-dependent luminescence of Tb 3+ ions in high calcium aluminosilicate glasses

Abstract

This study deals with the results on the concentration-dependent fluorescence properties of Tb 3+-doped calcium aluminosilicate (CAS) glasses of composition (100− x)(58SiO 2–23CaO–5Al 2O 3–4MgO–10NaF in mol%)- x Tb 2O 3 ( x=0, 0.25, 0.5, 1, 2, 4, 8, 16, 24, 32, 40 in wt%). The FTIR reflectance spectra suggested the role of dopant ions as network modifiers in the glass network. The fluorescence spectra of low Tb 3+-doped glasses have revealed prominent blue and green emissions from 5D 3 and 5D 4 excited levels to 7F j ground state multiplet, respectively. The glass with 2 wt% of Tb 2O 3 has exhibited maximum intensity of blue emission from 5D 3 level, while green emission from 5D 4 level has increased linearly up to 24 wt% and showed reduction in the rate of increase for higher Tb 2O 3 concentrations. The concentration quenching of blue emission ( 5D 3→ 7F j) is attributed mainly to the resonant energy transfer (RET) assisted cross-relaxation (CR) among the excited and nearest neighbour unexcited Tb 3+ ions in the glass matrix. The decline in rate of increase of green emission ( 5D 4→ 7F j) at higher concentrations has been explained due to a possible occurrence of cooperative energy transfers leading to 4f 8→4f 75d transition interactions. The blue and green emission decay kinetics have been recorded to compute the excited level ( 5D 3 and 5D 4) lifetimes, which confirmed the Tb 3+ concentration quenching of the blue emission in these glasses.