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Structural analysis by Rietveld refinement of calcium and lanthanum phosphosilicate apatites 被引量:1
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作者 hela njema Khaled Boughzala +1 位作者 Habib Boughzala Khaled Bouzouita 《Journal of Rare Earths》 SCIE EI CAS CSCD 2013年第9期897-904,共8页
Britholites with the general formula Ca10-xLnx(PO4)6-x(SiO4)xF2, (0≤x≤6) are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed tha... Britholites with the general formula Ca10-xLnx(PO4)6-x(SiO4)xF2, (0≤x≤6) are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed that the stability of these compounds de-creased as the substitution rate increased. The present work was an attempt to gain more information about the structural changes in-duced by the substitution, in order to understand the observed stability decrease. The samples were successfully synthesized as a sin-gle-phase apatite by a solid-state reaction between 1200 and 1400 °C. The structural refinement indicated that the La3+ions preferen-tially occupied the 6(h) sites. A progressive shift of F-along the c-axis outside its ideal position occurred as a result of the substitution increase. This might be the cause of the observed stability decrease, especially as the energies of the La-O, La-F and Si-O bonds are higher than those of Ca-O, Ca-F and P-O. The distribution of La3+ between the two non-equivalent sites was confirmed by the charge distribution method. 展开更多
关键词 britholites Rietveld refinement infrared spectroscopy charge distribution method rare earths
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