Effect of Alkali Ions on the Optical Absorption Characteristics of Co2+ ion in Binary Silicate Glasses

Abstract

Co2+ ion was found to produce a variety of colour shades ranging form pinkish blue to intense blue to greenish blue in a series of binary alkali silicate glasses. The optical absorption characteristics of divalent cobalt produce three strong bands in the visible and two weak bands in the near infrared region, respectively in lithium silicate, sodium silicate and potassium silicate glasses. In the present study, the molar extinction coefficients of Co2+ ion were calculated using Bouger-Beer's equation and the intensities of the bands were reported quantitatively in glasses at their wavelength maxima. The absorption bands in the molar extinction curves for Co2+ ion were found to shift more towards longer wavelengths with an increase in ionic radius of alkali ion on replacing lithium by sodium and sodium by potassium in glasses. The results were explained with reference to Ilse and Hartmann equation. Further, the values of molar extinction coefficients were found to increase with increasing basicity of the alkali silicate glasses as ionic radii of the alkali ions increase in order of K+> Na+> Li+ in the glass.