Abstract
The effect of addition of other elements to superconducting properties has been investigated. Various types of oxide complex are formed from additive element by a reaction with the superconducting YBaCuO phase. Nine oxide phases of BaZrO3, Ba2YNbO6, BaHfO3, Ba(Y0.5Ta0.5)O3, Al2Y4O9 , Ba2 SiO4 , Ga2Ba4O7, Ba2GeO4 and BaSnO3 have been confirmed to be formed. Especially the addition of Sn is very effective for improving critical current densities as well as for refining the microstructure. Oxide complex, BaSnO3 distributes finely in the grains and at grain boundaries. The AC magnetization measurements indicated that Sn addition causes intragrain critical current density to increase at 77 K in the magnetic fields up to 0.12 T. It exceeded 106 A/cm2 at 0.04 T for the 3-mol%-SnO2-added specimen. When the silver sheathed tapes were prepared by using the Sn-added powder, the transport critical current density is found to be improved by factor two comparing with non-additive tapes.
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