Raman scattering study of barium borate glasses and melts

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• 作者：Armenak A. Osipov ; ^{armik@mineralogy.ru} ; Leyla M. Osipova
• 关键词：A. Amorphous materials ; A. Glasses ; C. Raman spectroscopy
• 刊名：Journal of Physics and Chemistry of Solids
• 出版年：2013
• 出版时间：July, 2013
• 年：2013
• 卷：74
• 期：7
• 页码：971-978
• 全文大小：947 K

文摘

Glasses and melts of xBaO-(100?x)B₂O₃ (x=20, 25, 30, 35, 40, 45, 50, 55, 60 and 67 mol % ) composition have been prepared and studied using high-temperature Raman spectroscopy. It was shown that the structure of the glassy and molten samples with relatively low concentrations of barium oxide (x=20-35 mol % ) consists of [B?₄]^? charged tetrahedra (? is a bridging oxygen atom), B?₂O^? asymmetric triangles (O^? is a non-bridging oxygen atom) and B?₃ neutral units. The concentration of [B?₄]^? tetrahedra (N₄) monotonously decreases with increasing BaO content in the melts structure, whereas N₄ demonstrates a maximum at x¡Ö40 mol % in the glassy samples. pyroborate units appear at x¡Ý40 mol % , and orthoborate anions are also formed in the melts structure when x=60 and 67 mol % . The dominant mechanisms for the structural reorganizations generated by changes in temperature depend on the melt composition. The changes in the short range order (SRO) structures can be described by the [B?₄]^??B?₂O^? isomerization reaction at 25<x<40, whereas the dynamic equilibrium between structural units in the melts with x>50 is most likely described by the disproportionation reaction. In both cases, the equilibrium shifts to the right with an increase in temperature. Significant changes in the local structures of melts with a low concentration of barium oxide (x¡Ü20 mol % ) were not found.