Burnell, Victoria Anne (2011)
Ph.D. thesis, University of Birmingham.
This thesis presents work investigating the synthesis and characterisation of a range of mixed metal phosphates. The main aim of the project was to develop materials for the
remediation of nuclear waste. In light of this, the materials developed were subject to ion exchange studies and leach testing. The thermal behaviour of the phosphates and nature of the decomposition products were also investigated. This study demonstrates that the true
solid solution cannot be formed in any of the mixed metal series investigated, which included zirconium-titanium, germanium-titanium, germanium-zirconium, tin-titanium and
tin-zirconium. In all cases a miscibility gap was observed and the reasons for these were established. The co-precipitates that formed were characterised by a variety of analytical techniques which included powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), pair distribution function (PDF) analysis and X-ray fluorescence (XRF). Structural characterisation was undertaken using both traditional Rietveld analysis of synchrotron X-ray
powder diffraction data and PDF analysis of high energy synchrotron total scattering data. The results of the ion exchange studies yielded four exchanged products: strontium
exchanged zirconium phosphate, a strontium exchanged zirconium-titanium phosphate and two sodium exchanged titanium phosphate products. Although it was not possible to solve the structures of these phases, they were further characterised by a number of methods and their use as potential stores were investigated by leach testing. The strontium exchanged zirconium phosphate product demonstrated good strontium retention and is recommended
for further investigation as a possible strontium waste form.
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