Effects of Substituting Calcium for Yttrium on the Superconducting Properties of YBa2Cu3Oz Bulk Samples

摘要

We report systematic studies of AC magnetic susceptibility and transportproperties of Y(1-x)Ca(x)Ba2Cu3Oz bulk samples with 0\leq x\leq 0.4. Singlephase materials, reduction of carrier concentration and decrease of Tc to 85 Kwere obtained at doping levels up to 20%. For Y0.7Ca0.3Ba2Cu3Oz sample theimprovement of grains boundary transport and screening capabilities has beenobserved as a result of the optimal ratio between carrier concentration andimpurity phase BaCuO2 presence. The appearence of bulk pinning and nonlineareffects starting at the highest temperature were detected also.