EFFECT OF NA-CENTER-DOT-12AL(2)O(3)CENTER-DOT-61SIO(2) GLASS( ION ON THE STRUCTURE OF 27CAO)

Raman spectra and differential thermal analysis (DTA) were used to inv estigate structure of 27CaO . 12Al(2)O(3). 61SiO(2) glass with and wit hout Na2O. A new phenomenon is found: that is, the addition of a low c ontent of Na2O to 27CaO . 12Al(2)O(3). 61SiO(2) glass resulting in an increase of the aggregation extent of the glass network. Addition of t he Na+ ions to glass li:ads to the Al3+ ions, existing as network modi fiers, further entering as network formers. Phis results in the decrea se of the amount of nonbridging oxygen ions. Al3+ ions located as netw ork modifiers enter as network formers, which corresponds to the highe st value of the aggregation extent of the glass network. The nonbridgi ng oxygen ions will re-increase continuously with the Na2O content, wh ich corresponds to the continuous decrease of the aggregation extent o f glass network. The most effective content of the Na2O added is about 4.3 mol%. (C) 1998 Elsevier Science S.A. All rights reserved.