Spectroscopic investigations and physical properties of Mn2+ doped mixed alkali zinc borate glasses

Abstract Spectroscopic investigations on Mn 2+ doped 20ZnO +  x Li 2 O + (30− x )Na 2 O + 50B 2 O 3 (5 ≤  x  ≤ 25) (ZLNB) glasses reveal the non-linear behavior in their physical and structural properties. FT-IR spectra of ZLNB glasses reveal diborate units in the borate network. EPR spectra exhibit characteristic resonance signals of Mn 2+ ions. A well resolved six line hyperfine structure around g  = 2.02 corresponds to the sites of Type II, and a weak broad shoulder around g  = 2.7 followed by an unresolved intense signal at g  = 4.25 corresponding to sites of Type I are observed for their respective transitions. A large value of zero-field splitting parameter ( D ) is observed and it behaves non-linearly, reaches a maximum at x  = 15 mol% with increase in Li 2 O content. Δ g values reveal the ionic nature of glass systems. Optical absorption spectra suggest the distorted octahedral site symmetry of Mn 2+ ions in the host. Mixed alkali effect is evident in bandgap and Urbach energies.