Preparation and properties of binary rare-earth oxide-fluorides

Binary rare-earth oxide-fluorides, Ln2(1−x)Lnx′O3(1−x)F3x; Ln and Ln′ are different rare-earths, 0.5 ≤ x ≤ 0.78, have been investigated from the point of view of development of new type solid electrolyte based on the ideas of anionic hybridization of oxide ion and fluoride ion. The compounds of Nd2Ln2O3F6 was found to be applicable as an oxide ion-conducting solid electrolyte with much higher electrical conductivity than that of stabilized zirconia. The preparation, structure and electrical conducting properties of binary rare-earth oxide-fluorides are reviewed.