Influence of manganese ions on physical and spectroscopic properties of mixed alkali-alkaline earth oxide borate glasses

In this paper the studies on xMO-10Li2O-10Na2O-10K2O-(70-x)B2O3 [M=Mg, Sr and Ba] [x = 2, 4, 6, 8 and 10 mol%] glasses doped with manganese ions are reported. The physical and spectroscopic properties were investigated to know about the influence of the alkaline ions. The density values of all the glasses were found to increase with increasing alkaline earth oxide content while the values of molar volume were decreasing. The UV-VIS spectra of these glasses have shown single broad band which was assigned to the 6A1 g(S) -> 4T1 g (G) transition. The nonlinear variation of the optical band gap with the increase of alkaline earth oxides suggests nonlinear variation in the number of non-bridging oxygens. The EPR spectra demonstrated a predominant sextet hyperfine structure located around g = 2.0 which were ascribed to the octahedral symmetric octahedral Mn2+ ions. From the hyperfine splitting parameters (Aavg), it was noticed that the environment around Mn2+ ions is ionic. The number of spins participated in resonance (N) and magnetic susceptibility (chi) values were evaluated taking the high field g-values (g approximate to 2.0). It is interesting to note that, the observed zero field splitted (ZFS) values (D) are varying nonlinearly with the glass compositions and their values were increasing with the substitution of alkaline earth ions from Mg to Ba. The FTIR spectra of the glasses were analyzed in the range 400-2200 cm-1 to investigate the structural changes in the glass network.