In Situ Characterisation of Model UK Nuclear Waste Glasses by X-ray Absorption Spectroscopy Under Process Conditions

The local co-ordination environment of Zr in a model alkali borosilicate glass, of relevance to nuclear waste immobilisation, was studied by in situ X-ray absorption spectroscopy between 25 – 1060°C. Analysis of Zr K-edge XANES spectra, in comparison with those of well characterised standards, demonstrated, for the first time, the reversible transformation of ZrO6 to ZrO7 co-ordination polyhedra at high temperature. This observation was rationalised on the basis of the combined effects of network modifier cation diffusion and thermal expansion.

Structural and morphological characterization of rare earth modified lead titanate

Rare earth modified lead titanate powders Pb1-xRExTiO3 (REPT), x = 0.01, 0.05, 0.07 and RE = Yb, Y, were prepared by the Pechini method. The materials were calcined under flowing oxygen at different temperatures from 300 to 700 ºC. Nanostructured REPT were investigated using X-ray diffraction, scanning electron microscopy and surface area analysis (BET). The results suggest that the modifier cation incorporated into the system has notable influence in the microstructure and a notable decrease in the crystallite sizes.

Variation in P-O Bonding in Phosphate Glasses -A Neutron Diffraction Study

Two different lengths of P-O bonds in the PO4 units of phosphate glasses are found by neutron diffraction experiments of high resolution in real space. The two lengths are related to bonds of the phosphorus atom with the terminal and the bridging oxygen atoms. The mean lengths and widths of both P-0 distance peaks change as a function of the glass composition. In a large range, starting from vitreous P2O5 s up to the pyrophosphate composition, the behavior of the bond lengths is compared with that in the related crystals and with that resulting from ab initio calculations. The bond lengths depend not only on the species of the participating oxygen atoms and on the number of links of the concerning PO4 unit but also on the number of links of the neighboring PO4 unit and on the species of the modifier cation