Structure, microstructure and transport properties of B-doped YBCO system

A series of ceramic samples of Y1−xBxBa2Cu3Oy (YBBaCuO) with x = 0.00, 0.33 and 0.50 is synthesized by solid state reaction. The structure of all samples has been characterized by X-ray-diffraction (XRD) and transmission electron microscopy (TEM) techniques. The transport properties of the YBBaCuO samples have been measured by the standard four probe method in the temperature range from 20 to 300 K. The results show that the samples with x = 0 and 0.33 crystallize in an orthorhombic structure with slight decrease of the orthorhombicity. For x = 0.50, YBBaCuO crystallizes in a tetragonal structure. The microstructure is studied by transmission electron microscopy (TEM) in the imaging as well as in the selected area electron diffraction mode. Twin formation predominates for low x-values (x ⩽ 0.33) and the tweed structure appears at x = 0.33. The partial boron substitution leads towards a slightly overdoped regime, which is responsible for the decrease in the superconducting transition temperature (TC) of the doped system.