Fabrication of Ca-doped large grain Y-Ba-Cu-O superconductors

Doping the rare earth site in superconducting YBa/sub 2/Cu/sub 3/O/sub x/, (Y-123) with Ca generates additional positive charge carrier density in the Cu-O planes and, at a certain hole concentration, enhances the critical current density and irreversibility field of the material. 3 cm sized large, single grain samples of YBCO doped with various amounts of Ca have been fabricated by a top seeded melt growth technique. Very fine, sub-micron sized secondary phase particles of Y-211, which enhance flux pinning, have been observed in the (Y,Ca)Ba/sub 2/Cu/sub 3/O/sub y/ matrix without the addition of Pt. It is considered that Ca doping within the Y-211 phase is responsible for the refinement of these particles. In this paper we discuss the effect of Ca doping on growth rate, microstructural features and superconducting properties of large YBCO pseudo-crystals.