Theoretical technique to reconcile inconsistencies between crystallographic and chemical experimental | 9/5/2017 | Staff
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An ANSTO researcher has co-authored a novel theoretical approach to explain inconsistencies between crystallographic and chemical experimental data in the apparent transformation of a pyrochlore to defect fluorite in La2Zr2O7.

The model can be extended to understand the ageing of a large class of complex oxides, such as spinels, with practical applications ranging from solid oxide fuel cells to the design and management of nuclear waste forms.

Research - Scientific - Reports

The research was published in Scientific Reports.

Prof. Gordon Thorogood, a nuclear fuel cycle researcher, who collaborated with colleagues including David Simeone from CEA and Da Huo a PhD student and others said what was thought to be a phase change to defect fluorite structure, may, in fact, not be occurring.

Matrix - Mathematics - Summation - Peaks - Data

"Matrix mathematics suggested that a summation of peaks in the crystallographic data will make it look like the peaks have disappeared," said Thorogood.

The diffraction patters of La2Zr2O7 are due to the interference of scattering waves between shifted pyrochlore nano-domains.

Possibility - Surprise - Interest - Mechanism - Formation

"The possibility has been viewed with surprise but considerable interest as the physical mechanism responsible for the formation of a defect fluorite structure remains unclear."

In the investigation, they looked for a change in local symmetry that should have occurred with respect to decreasing grain size. Fine grained pyrochlore grains were sintered at different temperatures to probe order at different length scales.

Comparison - Electron - Energy - Loss - Spectroscopy

Comparison of electron energy loss spectroscopy (EELS) spectra collected near the lanthanum edge of the zirconium indicated local symmetry in the zirconium did not vary with respect to grain size....
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