Defect formation, distribution and size reduction of in melt-processed YBCO superconductors
Abstract
High critical current density in high temperature superconducting melt-processed Y-Ba-Cu-O (YBCO), which consists of a superconducting (Y123) phase matrix containing discrete (Y211) inclusions, can be achieved by control of the grain microstructure during processing. Y123 grain growth rate, Y211 particle size, morphology, distribution and density and the chemistry of the peritectically molten liquid are key parameters in the processing of this material and effectively determine its microstructure. In addition, YBCO processed with excess Y211 generates defects at the Y123/Y211 interface which form effective flux pinning sites and hence enhance . The effect of addition of Y211 on the sample microstructure, its distribution and refinement by chemical doping are discussed in detail in this review.