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Synthèses, caractérisations structurales et physico-chimiques de fluorures d'éléments tétravalents

Abstract : This work initially was devoted to the study of phase relationship in the ternary system KFMnF2- ZrF4. During the study in this system the compound of KMnZrF7 has been evidenced. The crystal structure determination allowed to show the opportunity to substitute two rare earths Ln3+ for the couple Zr4+ and Mn2+ without any charge compensation. This study also allowed to clarify the phaserelationship in the binary system KF-ZrF4. The study of the insertion of lithium ions in tetravalent lanthanides or actinides fluorides led to the obtention of a new phase Li5,5Ce12F50. The crystal structure determination revealed the simultaneous presence of Ce4+ in 8 and 9-coordination building tetrameric units as well as Ce3+ and Ce3+/Ce4+ (in statistical distribution) encompassed in isolated in 8-coordination polyhedra. In the light of this result we have revised the study of the LiM4F17 phases initially reported as belonging to the binary systems LiF-MF4 (M = Ce, U, Th) and shown that these phases were in fact mixed valence (III/IV) fluorinated compounds. A new method of mixed valence fluorides synthesis by electrochemical intercalation of lithium ions in the host matrix has been developed. To this aim containing Ce, Tb, U, Th have been tested. Finally this research work has been extended to the study of fluorozirconates and fluoroterbates of formula LiLnMF8 (M = Zr and Tb). The structural characterization of these LiLnMF8 compounds allowed to show the existence of structural relationships with the fluorides LiNaY2F8, LiNaYb2F8 and BaY2F8. These compounds LiLnMF8 (M = Zr and Tb) exhibit open structures susceptible to enhance the diffusion of the alkaline ions. Thus the intercalation and desintercalation of the alkaline ions in the LiYTbF8 host matrix allowed the obtention of new mixed valence fluorinated compounds and open the route to new synthesis processes.
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Submitted on : Monday, July 16, 2012 - 11:00:39 AM
Last modification on : Tuesday, December 14, 2021 - 10:38:06 AM
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  • HAL Id : tel-00718104, version 1

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Elise Mapemba Moulakou. Synthèses, caractérisations structurales et physico-chimiques de fluorures d'éléments tétravalents. Chimie organique. Université Blaise Pascal - Clermont-Ferrand II, 2007. Français. ⟨tel-00718104⟩

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