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

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(2)O(3)-4MgO-10NaF in mol%)-x Tb(2)O(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 5133 and 5134 excited levels to (7)F(j) ground state multiplet, respectively. The glass with 2 wt% of Tb(2)O(3) has exhibited maximum intensity of blue emission from 5133 level, while green emission from (5)D(4) level has increased linearly up to 24 wt% and showed reduction in the rate of increase for higher Tb(2)O(3) concentrations. The concentration quenching of blue emission ((5)D(3)->(7)F(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 ((5)D(4)->(7)F(j)) at higher concentrations has been explained due to a possible occurrence of cooperative energy transfers leading to 4f(8)-> 4f(7)5d transition interactions. The blue and green emission decay kinetics have been recorded to compute the excited level ((5)D(3) and (5)D(4)) lifetimes, which confirmed the Tb(3+) concentration quenching of the blue emission in these glasses. (c) 2009 Elsevier B.V. All rights reserved