Electrochemical fluorination of La₂CuO₄ : a mild "chimie douce" route to superconducting oxyfluoride materials

Marie-Hélène Delville (1) , David Barbut (1) , Alain Wattiaux (1) , Jean-Marc. Bassat (1) , Michel Ménétrier (1) , Christine Labrugère (1) , Jean-Claude Grenier (1) , Jean Etourneau (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The fluorination of La₂CuO₄ was achieved for the first time under normal conditions of pressure and temperature (1 MPa and 298 K) via electrochemical insertion in organic fluorinated electrolytes and led to lanthanum oxyfluorides of general formula La₂CuO₄F_x. Analyses showed that, underneath a very thin layer of LaF₃ (a few atomic layers), fluorine is effectively inserted in the material's structure. The fluorination strongly modifies the lanthanum environment, whereas very little modification is observed on copper, suggesting an insertion in the La₂O₂ blocks of the structure. In all cases, fluorine insertion breaks the translation symmetry and introduces a long-distance disorder, as shown by electron spin resonance. These results highlight the efficiency of electrochemistry as a new “chimie douce” type fluorination technique for solid-state materials. Performed at room temperature, it additionally does not require any specific experimental care. The choice of the electrolytic medium is crucial with regard to the fluorine insertion rate as well as the material deterioration. Successful application of this technique to the well-known La₂CuO₄ material provides a basis for further syntheses from other oxides.

Domaines: Matériaux

Marie-Hélène Delville, David Barbut, Alain Wattiaux, Jean-Marc. Bassat, Michel Ménétrier, et al.. Electrochemical fluorination of La₂CuO₄ : a mild "chimie douce" route to superconducting oxyfluoride materials. Inorganic Chemistry, 2009, 48 (16), pp.7962-7969. ⟨10.1021/ic900912d⟩. ⟨hal-00418911⟩