The short range structure of 0.05Al2O3.xNa 2O.(0.95-x)B2O3 glasses (0.10<x<0.45) has been investigated using molecular dynamics calculations employing a fully ionic model. Regardless of x, the coordination number of oxygen atoms around the Al atom was approximately four. It was found that these Al atoms are present as network formers of AlO4 units in the glasses in the same manner as are BO4 units, and that they cause a decrease of the coordination number of O around Na. It is suggested that the exclusively formed AlO 4 units may suppress the conversion of the BO3 unit to the BO4 unit caused by an increase of Na2O. The decrease of the fraction of four coordinated boron atoms, N4, due to the addition of Al2O3 is supported by the results obtained from preliminary neutron diffraction measurements.
|Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B
|Published - 8月 1 2006
ASJC Scopus subject areas