Influence of magnesium oxide on the physical and spectroscopic properties of manganese doped sodium tetra borate glasses

Abstract

The effect of alkaline earth oxide on sodium tetraborate was analyzed by fabricating a range of glasses depicted by the formula x MgO-(40-x)ZnO-59.5Na2B4O7-0.5MnO2. Basic character was analyzed and confirmed by XRD tests.Decline in density is attributed to the replacement of high molecular mass ZnO by a relatively less molecular mass MgO. The volume enlargement is discussed in terms of increased bond lengths and induced non- bridging oxygen atoms. Parameters like refractive index, reflection loss, molar refractivity, electron polarizability are obtained from existing relations. All these are indirectly depends on density and molar volume and hence their nature. Optical studies revealed indirect kind of transitions in these glasses ranging the values of optical energy gap between 2.913–3.15 eV and Urbach energy (ΔE) 0.342–0.276 eV showing greater stability of glasses.Mn2 +ion in its d5 state revealed a well resolved sextet centered around g"2.032 indicating Mn2+ ions are in octahedral (Oh) environment resulted from jumps between lower doublet energy states. The resonance of g≈ 2.99 and g≈ 4.22 are related to rhombic surroundings of the Mn2+ and jumps between middle kramers doublets. The value of hyperfine split ‘A′ and Δg= (ge-g) are indicative of ionic bonding between Mn2 + ions and oxygens. Zero field splitting parameter ‘D′ decreases from x = 0 to x = 30 mol% and then increased for x = 40 mol%. Magnitude of unpaired spins(N) participating in the resonance and paramagnetic susceptibility(c) are calculated. FTIR and Raman studies are conducted. FTIR spectra revealed the structural changes from BO4 to BO3 by increasing MgO content. From FTIR and Raman studies it is established that MgO is acting as modifier in the given glass composition.