Mixed alkali effect in physical and optical properties of xK2O-(25-x) Na2O-12.5MgO-12.5BaO-50B2O3 Glasses

Publication date: Available online 6 November 2015 Source:Journal of Taibah University for Science Author(s): G. Srinivas, B. Ramesh, J. Siva Kumar, Md. Shareefuddin, M.N. Chary, R. Sayanna Borate glasses with the composition xK2O-(25-x) Na2O-12.5MgO-12.5BaO-50B2O3 (x=0, 5, 10, 15, 20 and 25mol %) were prepared by the melt-quenching technique and were characterized by using x-ray diffraction technique at room temperature. From the optical absorption spectra direct forbidden, direct allowed, indirect allowed, indirect forbidden energy gaps, Urbach energy, refractive index (n), dielectric constant (ɛ), reflection loss (R), molar refraction (Rm) and molar polarizability α m values of all the glass samples were evaluated. Rm, a m and Λ th increase with increasing of K2O content. The values of R, ɛ and n increase up to x=10 mol% and then decrease above x=10 mol%, which may be due to the mixed alkali effect. Density and molar volume values show opposite behaviour and vary nonlinearly with the K2O content which manifests the mixed alkali effect in the present glass system. The infrared (IR) spectra of the borate glasses reveal the existence of 3 and 4- coordinated boron atoms. The specific vibrations of Na–O, K–O, Mg–O, and Ba–O bonds were observed in IR study.

Source: Journal of Taibah University for Science - November 7, 2015 Category: Science Source Type: research