We present X-ray diffraction and magnetization measurements of the compound [Y0.8Ca0.2]SrBaCu3-x(BO3) xO7-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 (BO3)3- in the Cu(1) site of [Y0.8Ca0.2]SrBaCu3O 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 [Y0.8Ca 0.2]SrBaCu3-x(BO3)xO 7-δ with the indication of the borate occupying the Cu(1) site. The TC were determinate by the measurements of magnetization versus temperature using a SQUID detection system, which indicates the TC vary according with the concentration of borate. For instance to x=0.10; 0.30 and 0.50, the TC's are 35, 38 and 28 K, respectively. © 2005 Elsevier Ltd. All rights reserved.