X-ray and neutron scattering studies of the structure of copper phosphate glasses

The structure of copper phosphate glasses (CuO)(x)(P2O5)(1-x) with 0.15 <= x <= 0.54 was studied by x-ray and neutron diffraction. Dry samples were prepared using sealed silica ampoules for melting. Details of the P-O and O-O pair correlations indicate the rupture of the phosphate network of corner connected PO, tetrahedra with increasing CuO content. The Cu-O first neighbour peaks are located at 0.194 nm where total coordination numbers including all distances <similar to 0.26 nm are similar to 4 and do not change with CuO content. The structure factors of the copper phosphate glasses studied and zinc phosphate glasses measured earlier (Cu2+ and Zn2+ ions possess equal radius and similar scattering power) show great similarity in the Q-range > 60 nm(-1). For smaller Q, similarity of the structure factors exists only for the glasses with x congruent to 0.33 but not for those with x congruent to 0.50. This fact indicates the medium range order of the copper phosphate glasses to correspond to a network formed Of PO4 units and six-coordinated Cu2+ ions but not to a network with PO, and CuO4 tetrahedra. The CuO, octahedra are assumed to exist in strong tetragonal distortions according to Jahn-Teller where the two longer Cu-O distances are not accessible to our analysis.