Reactive nanophase oxide additions to melt-processed high-T/sub c/ superconductors

Nanophase TiO/sub 2/ and Al/sub 2/O/sub 3/ powders were synthesized by a vapor-phase process and mechanically mixed with stoichiometric YBa/sub 2/Cu/sub 3/O/sub x/ and TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ powders in 20 mole% concentrations. Pellets produced from powders with and without nanophase oxides were heated in air or O/sub 2/ above the peritectic melt temperature and then slowly cooled. At 4.2 K, the intragranular critical current density (J/sub c/) increased dramatically with the oxide additions. At 35-50 K, effects of the oxide additions were positive, but less pronounced. At 77 K, the additions decreased J/sub c/, probably because they depressed the transition temperature.<
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