Effects of substituting calcium for yttrium on the superconducting properties of YBa2Cu3Oz bulk samples

Abstract We report systematic studies of AC magnetic susceptibility and transport properties of Y 1− x Ca x Ba 2 Cu 3 O z bulk samples with 0⩽ x ⩽0.4. Single phase materials, reduction of carrier concentration and decrease of T c to 83 K were obtained at doping levels up to 20%. For Y 0.7 Ca 0.3 Ba 2 Cu 3 O z sample the improvement of grains boundary transport and screening capabilities has been observed as a result of the optimal ratio between carrier concentration and impurity phase BaCuO 2 presence. The appearance of bulk pinning and nonlinear effects starting at the highest temperature were detected also.