Combined neutron and X-ray scattering study of phosphate glasses

The advantage of high resolving power and of different contrast of total X-ray and neutron diffraction (XRD and ND) experiments is demonstrated in studies of the short- and medium-range order of some phosphate glasses. Details of two different P–O bonds are detected using Q-ranges up to 500 nm−1. A different contrast is used to resolve Me–O distances in the range of the O–O peaks at 0.25 nm where Me is the modifier atom. In many cases the Me–O peaks are asymmetric. Reverse Monte Carlo simulation is applied to combine X-ray and neutron scattering data for extracting features of the medium-range order. Increasing Me–O distances changes the mutual order of the Me atoms in metaphosphate glasses with the tendency of a clustering of Me sites due to MeOn polyhedra sharing oxygen atoms. But if compared with the alternating order of Me and P sites the clustering of the Me sites is a minor effect. Me–Me first-neighbor distances are little affected if the fraction of modifier oxide is varied while the number of Me–Me neighbors is clearly changed.