THE DEPENDENCE OF STRUCTURAL PECULIARITIES IN BINARY PHOSPHATE-GLASSES ON THEIR NETWORK MODIFIER CONTENT

X-ray diffraction measurements were performed on four (MeO)(x)(P2O5)(( 1-x)) glass series, with Me = Zn, Mg, Ca, Ba, and x ranging from about 0.05 to 0.6. The parameters for the Me-O coordination sphere are dete rmined. Abrupt changes in the ionic volume fraction are found for the glasses, with different Me ions, at certain compositions which correla te with the behaviour of the Me-O coordination sphere. These phenomena can be explained in terms of a model based on the chemical characteri stics of P2O5 and on the interplay between the number of non-bridging oxygen atoms per Me cation and changes in the type of the MeO(m) polyh edron.