YBACUFEO5+DELTA - A NOVEL OXYGEN-DEFICIENT PEROVSKITE WITH A LAYER STRUCTURE

A novel ordered oxygen-deficient perovskite with a layer structure, YBaCuFeO//5// plus // delta , was isolated. It was characterized by chemical analysis, Moessbauer spectroscopy, and magnetic susceptibility measurements versus temperature. Its structure was determined by powder neutron diffraction. It crystallizes in the tetragonal system with a equals 3. 867 Angstrom approximately equals a//p and c equals 7. 656 Angstrom approximately equals 2a//p. The structure can be described as formed of left bracket CuFeO//5 right bracket infinity double layers of corner-sharing CuO//5 and FeO//5 pyramids, perpendicular to c. The cohesion between the layers is ensured by yttrium planes whereas the barium ions are located inside the layers. The relationships of this structure with those of YBa//2Cu//3O//7// minus // delta and LaBa//2Cu//3O//7// minus // delta are discussed.