Structural investigation and physical properties of RO-ZnO-Li2B4O7-K2B4O7 (RO= SrO and BaO) glasses

Glass samples 10RO-30ZnO-xLi2B4O7-(60-x) K2B4O7 (RO=SrO and BaO) with alkali tetra borates varying from 0 to 60 mol% were produced by traditional quenching procedure. Peak free broad X-ray diffraction patterns established the amorphous feature of glass samples. FTIR and Raman spectroscopic analysis had shown existence of BO3 and BO4 structural groups along with other borate units. The BO3 ⇔ BO4 conversion rate was not much affected with variation in one of the alkali-tetraborates. EPR spectra of copper doped glasses confirmed the ground state of Cu2+ ions as 2B1g. Physical and optical properties namely density, molar volume, refractive index, molar refractivity, optical band gap and Urbach energy values were found to be composition dependent. The inflections observed in density, and other optical properties around equal mol% of alkali oxides in the glass system were attributed to structural modifications and mixed alkali effect. These results exposed the structural variations caused due to competitiveness between the two different alkali and alkaline oxides in occupying the geometrical positions of the borate glass network.