The orthorhombic-to-tetragonal phase transition in YBa₂(Cu_1−xFe_x)₃O_7−y

Abstract

The phase transition YBa₂(Cu_1−x Fe _x )₃O_7−y (0⩽x⩽0.05) prepared through solid-state reaction was studied with X-ray diffraction analysis and optical microscope. It was found that the orthorhombic-to-tetragonal phase change was induced between x=0.02 and x=0.03 by X-ray diffraction. The phase transition was also identified by the disappearance of striations in plate-like grains under polarized light. The microstructures of the specimens with compositions of x=0.01 and x=0.02 showed faint striation images. It is considered that a mixture of the orthorhombic and tetragonal phase exists in these compositions.