Morphology of Y1Ba2Cu3Oz and Y0.7Ca0.3Ba2Cu3Oz bulk samples depending on Ca - substitution

The effects of calcium substitution on the microstructure, composition and morphology of superconducting bulk samples were analyzed by means of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) techniques. We have shown evidence that a Ca concentration 0.3 is the critical substituted value for YBCO system, in respect of the optimium superconducting properties.