Determination of local structure in mixed lanthanoid phosphate solid solutions by X-ray absorption spectroscopy
Determination of local structure in mixed lanthanoid phosphate solid solutions by X-ray absorption spectroscopy
Lozano-Rodriguez, M. J.; Arinicheva, Y.; Heuser, J.; Kvashnina, K.; Neumeier, S.; Scheinost, A. C.
In the 21st century, scientific challenges are required for the disposal of high-level nuclear waste in deep geological formations. Ceramic waste forms like monazite and xenotime, are natural lanthanoid phosphate minerals containing U and Th. When light lanthanoids are involved the monazite structure forms; when heavy lanthanoids are present, the xenotime structure predominates. X-ray absorption spectroscopy was carried out to elucidate the structural changes induced by different lanthanoids when mixed lanthanoids phosphates are formed. EXAFS measurements for La1-xEuxPO4 solid solutions around La and Eu, show the flexibility of the monazite structure when two light lanthanoids are hosted. The La-O distances in the first coordination shell and the first metal-metal distances decrease with increasing Eu content; while the Eu-O local coordination remains unchanged. Additionally, HR-XANES shows an increase on the white line in the absorption coefficient with increasing Eu content, suggesting a change in the valence electron distribution. However, EXAFS measurements of Sm1-xTbxPO4 solid solutions around the Sm, show significant differences between low and high Tb content.
Keywords: EXAFS; phosphate solid solutions; lanthanoids
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
Related publications
- DOI: 10.1107/S1600577520014265 is cited by this (Id 23080) publication
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Lecture (Conference)
E-MRS 2015 Spring Meeting, 11.-15.05.2015, Lille, France
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