A career in diffraction: probing the structure of phosphate glasses
Results of neutron and x-ray diffraction studies on phosphate glasses performed by the author during the last three decades are reviewed. The length scales under consideration start from 0·010 nm, the distance difference of bridging and nonbridging P–O bonds, where changes of 0·002 nm are significant. Diffraction is superior in determining the coordination numbers and lengths of oxygen bonds with many modifier, conditional glass-former, and glass-former ions. Much benefit is taken from the high resolving power in real-space that is due to the large available range of magnitude of scattering vector and the change of contrast of x-ray and neutron scattering. Peculiar changes of the coordination numbers and properties (packing densities, etc) gave rise to an atomic model for phosphate glasses, MyOz–P2O5, where the available number of nonbridging oxygens per M atom is the critical value. The model is illustrated for several examples (M=Zn, Sn, rare earths, Ge, Te). Diffraction experiments are used for studying the medium range order, whether shapes and positions of the first diffraction peaks are analysed or far reaching correlations of strongly scattering atomic species are extracted. Alkali germanophosphate glasses bear a first scattering peak at 8 nm–1 that was related to interatomic distances of ∼1·0 nm and which is explained with a sophisticated model of the medium range structure. The Re–Re correlations of binary rare earth glasses 25Re2O3–75P2O5 have been determined by reverse Monte-Carlo method. Their excellent agreement with the Tb–Tb correlations determined by colleagues suggests interpreting all the details of these correlations up to lengths >1·0 nm.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Article Media
Document Type: Research Article
Publication date: October 1, 2019