High Temperature NMR study of the local structure of molten LaF3–AF (A=Li, Na, K and Rb) mixtures

Anne-Laure Rollet (1) , Stéphanie Godier , Catherine Bessada (2)

1 PECSA - Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques
2 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation

The local structure of molten lanthanum alkali fluorides binaries have been studied using HT NMR technique. The chemical shift of 19F, 23Na and 139La in solid and in liquid have been compared for AF (A=alkali) and LaF3. In pure molten alkali fluorides, the polarisability of anion–cation pairs appears to be a key parameter to depict the observed evolution of 19F chemical shifts. The influence of composition have been also studied by measuring the chemical shifts in molten LaF3–AF as function of LaF3 concentration. A strong influence of the alkali influence is observed. The coordination number of lanthanum is decreased versus AF amount all the more since the alkali atomic number is high. Moreover, the more polarisable the alkali, the less bridging fluorines between LaFx units.

Mots clés: molten; salt; molten fluoride; NMR; 139La; 19F; liquid structure

Domaines: Chimie inorganique

Anne-Laure Rollet, Stéphanie Godier, Catherine Bessada. High Temperature NMR study of the local structure of molten LaF3–AF (A=Li, Na, K and Rb) mixtures. Physical Chemistry Chemical Physics, 2008, 10, pp.3222-3228. ⟨10.1039/b719158h⟩. ⟨hal-00440181⟩