Superconductivity in the system [Y0.8Ca0.2](SrBa)Cu3−x(BO3)xO7−δ with 0.1≤x≤0.5

Abstract

Abstract We present X-ray diffraction and magnetization measurements of the compound [Y 0.8 Ca 0.2 ]SrBaCu 3− x (BO 3 ) x O 7− δ with 0.1≤ x ≤0.5. Samples were prepared by the solid state reaction method under normal conditions of pressure and temperature, and replacing amounts of borate (BO 3 ) 3− in the Cu(1) site of [Y 0.8 Ca 0.2 ]SrBaCu 3 O 7− δ . The X-ray diffraction patterns reveal a monophasic compound. Rietveld refinements were done with the consideration of an orthorhombic crystalline model, belonging to Pmmm spatial group for most the samples; nevertheless there are significant variations in the cell's parameters. We propose the crystalline structure for the [Y 0.8 Ca 0.2 ]SrBaCu 3− x (BO 3 ) x O 7− δ with the indication of the borate occupying the Cu(1) site. The T C were determinate by the measurements of magnetization versus temperature using a SQUID detection system, which indicates the T C vary according with the concentration of borate. For instance to x =0.10; 0.30 and 0.50, the T C 's are 35, 38 and 28 K, respectively.