Preparation of BiSrCaCuO superconductors by laser floating zone melting technique

Abstract The growth of crystal fibers of BiSrCaCuO superconductors with different nominal compositions by the laser floating zone melting technique has been studied. The seeding and feeding rods for the process were prepared by common solid-state sintering. The crystals were grown with pulling rates and temperatures of the molten zones in the ranges of 0.17–10 mm/min and 900–950°C, respectively. The as-grown crystals were 0.5–1.5 mm in diameter and show high densities and aligned structures with the a-b planes parallel to the growth axis, which would be greatly helpful in reducing the weak links between grain boundaries and thus enhance transport critical current density. It was found that after a suitable post-heat-treatment (e.g. 860°C/10 h + furnace cooling), the samples with nominal composition BiSrCaCu 2 O y , gave a superconducting transition temperature of 85 K ( T c , zero ) and a rather high transport critical current density of 1800 A/cm 2 at 77 K and zero field. These samples were also characterized by X-ray diffraction, optical and scanning electron microscopies and electron probe.