Structural transformations in Y-Ba-Cu-Ti-O metal oxides accompanying substitution of titanium for Y and Cu

Abstract

Taking into account changes in the Cu charge states, general characteristics and distinctive features of structural transformations typical of high-temperature superconducting and ferroelectric phases in Y-Ba-Cu-Ti-O ceramic samples are studied. It is shown that with substitution of titanium for Y and Cu the concentration of Jahn-Teller ions Cu2+ detected by EPR technique does not rise higher than 10%. According to X-ray spectroscopy data, the Cu charge state lowers from Cu2.2+ to Cu0.5+ with increasing titanium content. It is found by X-ray diffraction studies that with increasing Ti content, the fraction of the layered structure containing (00l) planes of orthorhombic structure decreases and the growth of planes of the (11l) type pertaining to tetragonal structure is stimulated. The structural phase transition from the orthorhombic to tetragonal crystal structure mainly occurs in the range x=0.3–0.5.