Synthesis from solutions and properties of various metal fluorides and fluoride salts

Parts of the recent advances in the search of new fluorides or fluoride sal ts, at the Laboratoire des Fluorures in Le Mans, are presented. Hydrotherma l synthesis in sub-critical or super-critical conditions is mainly used to obtain rare earth (RE), Al, Ga, In or 3d transition fluorides or fluoride s alts (borates, carbonates, phosphates or silicates). Open structures are ob tained by low temperature crystallisation from solutions (delta-(H3O)RE3F10 . xH(2)O) and, probably, by decomposition of hybrid organic-inorganic fluor ides D . MF5 (D = diprotonated aliphatic diamine), prepared by micro-wave h eating of the solutions. Non-centrosymmetric phases are evidenced in fluori de carbonates and fluoride berates: K4RE2(CO3)(3)F-4 and M-2(BO3)(OH)(0.75) F-0.25; the magnetic properties of several iron fluoride phosphates are fou nd to be governed by super or super-superexchange interactions. (C) 2001 El sevier Science B.V. All rights reserved.