APT: solubility limits of phosphorous pentoxide

Atom Probe Tomography (APT) has been utilised to investigate the microstructure of two model borosilicate glasses designed to understand the solubility limits of phosphorous pentoxide (P₂O₅).

This component is found in certain high-level radioactive defence wastes destined for vitrification, where phase separation can potentially lead to a number of issues relating to the processing of the glass and its long-term chemical and structural stability.

In a 3.0 mol%P₂O₅-doped glass, both visual inspection and sensitive analysis of the APT data show homogenous microstructures, while raising the content to 4.0 mol% initiates the formation of phosphorous-enriched nanoscale precipitates.

This study*, funded by NNUF confirms the expected inhomogeneities and phase separation of these glasses and offers routes to characterising these at near-atomic scale resolutions using APT.

This work was an NNUF-funded study in collaboration with colleagues at Sheffield-Hallam University.  From Oxford the key individuals are Przemyslaw Klups, Michael P Moody and Paul A J Bagot.  

* 'Atom Probe Tomography investigation of clustering in model P₂P₅-doped borosilicate glasses for nuclear waste vitrification', as published in Microscopy & Microanalysis.