Raman and Infrared Spectroscopy and Some Physical Properties of Glasses in the MgO-Al₂0₃-B₂0₃ System

Abstract

Glass-forming region were determined in the Mg0-Al₂0₃-B₂0₃ system by the melt quenching method. Phase separation occurred at B₂0₃ rich compositions. Raman spectroscopy and IR spectroscopy measurements revealed that boroxol ring moieties exist at the B₂0₃ rich compositions and that diborate moieties of 4-fold coordinated boron exist at MgO rich but Al₂0₃ poor compositions. Pyroborate or orthoborate moieties of 3-fold coordinated boron were found at MgO rich compositions in the ternary systems. With the increase in the Al₂0₃ content, the concentration of diborate is reduced and Al0₄-tetrahedra are formed. The chemical shift measurements confirmed the variation of the coordination number of Al³⁺ ion in the Mg0-Al₂0₃-B₂0₃ system. From the comparison between the Mg0-Al₂0₃-B₂0₃ and CaO-Al₂0₃-B₂0₃ systems, it was I concluded that Mg0-Al₂0₃-B₂0₃ system has not formed a continuous network of 6-membered rings consisting of Al0₄-terahedra.
The variations of the peak shifts associated with pyroborate or orthoborate moieties suggested that Al³⁺ ions might in part be incorporated in these moieties. The smooth variation in density and refractive index of the glass with composition suggested that the structure changed continuously with composition.