Spectral analysis of Mn2+, Co2+ and Ni2+: B2O3-ZnO-PbO glasses

This paper reports on the spectral properties of Mn2+, Co2+ and Ni2+ ions doped B2O3-ZnO-PbO glasses. XRD, FT-IR spectra and DSC profiles of these glasses have also been carried out, and the FT-IR profiles have shown the presence of both BO3 and BO4 units. It is interesting to notice that the FT-IR peak positions are slightly shifted towards higher energy with an increase in transition metal ion concentration change. From the measured DSC thermograms, glass transition (T(g)), crystallization (T(c)) and temperature of melting (T(m)) have been evaluated. From the UV absorption spectra of Mn2+, Co2+ and Ni2+ ions doped glasses, both direct and indirect optical band gaps have been calculated. The visible absorption spectra of Mn2+:glasses have shown a broad absorption band at 520 nm (6A1g(S) --> 4T1g(G)); with Co2+ ions one absorption band at 605 nm (4A2(4F) --> 4T1(4P)) and another at 1450 nm (4A2(4F) --> 4T1(4F)); and for Ni2+:glasses three absorption bands at 420 nm (3A2g(F) --> 3T1g(P)), 805 nm (3A2g(F) --> 1Eg(D)) and 880 nm (3A2g(F) --> 3T1g(F)) have been observed. For Mn2+:glasses, upon excitation with 262 nm, a green emission (539 nm) with a slight blue shift; and with 392 nm, a green emission (534 nm) with a slight red shift with Mn2+ ions concentration change (0.2-0.5 mol%) has been observed. This green emission has been assigned to (4T1(G) --> 6A1(S)) d-d transition of Mn2+ ions that are in tetrahedral co-ordination. For 0.5 mol% Co2+ ions doped glass, upon excitation with 580 nm, a red emission (625 nm) has been observed which originates from 2E(2G) --> 4A2(4F) transition of Co2+ ions in tetrahedral co-ordination. For Ni2+ ions doped glasses upon excitation with 420 nm, a green (577 nm) and red (670 nm) emissions are observed and are assigned to (1T2g(D) --> 3A2g(F)) and (1T2g(D) --> 3T2g(F)) d-d transitions of Ni2+ ions in octahedral co-ordination.