AN X-RAY STUDY OF PHOSPHATE-GLASSES OF THE COMPOSITION [M(PO3)(2)](N) (M=ZN, CU, MN, CA AND MG)

An X-ray scattering study was undertaken of five phosphate glasses of the general formula [M(II)(PO3)(2)](n), where M(II) = Zn, Cu, Mn, Ca and Mg. Their melting temperatures and macroscopic densities as well as X-ray scattering curves indicate an anomalous behaviour for the Mg phosphate glass. The first scattering peak (FSP) of the X-ray pattern is located for all except the Mg phosphate glass at 1.7 Angstrom(-1) while for the latter its position is 1.55 Angstrom(-1). Hence medium-range density fluctuations of the order 5 Angstrom may be expected in the Mg phosphate glass and of the order of 4.5 Angstrom for the remaining glasses. The radial electron density distribution curves are all characterized by the P-O coordination sphere at 1.55 Angstrom resulting from the basic PO4/2 building block. The Me-O distances exhibit a linear dependence on atomic number, with the exception of the Mg phosphate glass (Mg-O = 1.9 Angstrom).