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Thermal expansion and transition temperature of glasses in the systems BeO–Al2O3–B2O3and MgO–Al2O3–B2O3

Journal of Non-Crystalline Solids
Publication Date
DOI: 10.1016/j.jnoncrysol.2007.01.065
  • Glass Transition
  • Thermal Expansion
  • Glasses
  • Borates


Abstract Researches were conducted for glasses in the systems BeO–Al 2O 3–B 2O 3 and MgO–Al 2O 3–B 2O. The following characteristics have been determined: thermal expansion coefficient within 20–300 °C, structural thermal expansion coefficient (STEC) and glass transition temperature. The discussed properties of Be-aluminoborate and Mg-aluminoborate glasses have been compared with those of Ca-, Sr- and Ba-aluminoborate glasses. TEC of studied glasses gets higher going from Be-aluminoborate glasses to Ba-aluminoborate ones, but T g decreases under the same succession. The dependence of STEC on the nature of a given cation is more complicated. The pattern of dependence of the properties on composition is due to changing the boron coordination number with respect to oxygen, which is the main network-former, and to competition between the aluminium and boron for the oxygen brought by an ion-modifier. The difference between the effect of one ion-modifier and that of another is determined by decreasing the radius of an ion and increasing its electric field strength in the succession from Ba 2+ to Be 2+. The ions of Be and Mg can also act as network-former to some extent.

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