Investigation of magnetic properties of superconductors Y0.98−xCaxCo0.02Ba2Cu3O7−δ

The effect of Co2+, 3+ and Ca2+ substitution in Y3+ site in YBa2Cu3O7−δ superconductor has been studied. The series of high temperature superconducting samples of Y1−y−xCoyCaxBa2Cu3O7−δ with 0 ≤ x ≤ 0.015 and y = 0.020 were prepared by solid-state reaction method. The samples were characterized for phase purity and lattice parameter variations by X-ray diffraction. The AC susceptibility curves, χ'(T), show that in reserving cobalt fixed sample with the optimum Tc, by substitution of divalent Ca2+ at the trivalent Y3+ site no sensitive increasing happen in the superconducting transition temperature.