| Results are reported on using additives in processing YBa2Cu 3O7--delta (YBCO) superconductors for enhanced grain orientation and texturing. Processing below and above the YBa2Cu 3O7--delta (YBCO) peritectic was examined in the presence of additives. Sol-gel coating techniques were developed to incorporate additives on YBCO powders at a nanometer scale. Processing methods included diffusion couple assisted texturing (DCAT), hot forging and melt processing.;Processing below the peritectic with sol-gel TiO2 additions resulted in the formation of liquid phases in YBCO sintered at 930°C and 960°C. Increased density, grain size and anisotropy was achieved with 2.5 mole % addition when sintered at 930°C. TiO2 additions altered the magnetic susceptibility with an optimum response occurring with 2.5 mole % addition when sintered at 930°C.;A number of diffusive couple impurity oxides (i.e., SiO2, SnO2, Bi2O3, TiO2, Sb2O 3, In2O3, Nb2O5, and Pr 6O11) promoted exaggerated grain growth and domain formation through a liquid phase intrusion below 980°C. DTA revealed a endothermic reactions associated with formation of a liquid phase in YBCO with impurity oxides present. Impurity oxides forming lower temperature eutectics, i.e., Bi2O3 and SiO2, formed larger domains with greater 211 particle concentrations.;Phase evolution of melt quenched (MQ) precursors, as studied by DTA and real time dynamic hot stage XRD, indicated 211 formation prior to YBCO peritectic decomposition. The YBCO phase formed below 800°C with BaCuO2 present by reaction of available yttrium. YBCO phase solidification temperature increased with Pt present and decreased with yttrium addition up to 10 mole %. Yttrium significantly enhanced melt textured density to ≥95% theoretical. The addition of 5 mole % Y2Cu2O5 (202) to MQ powders enhanced densification and increased 211 weight fraction.;Higher densities and larger domain size resulted using MQ precursors with BaCuO2-DCAT coupling. The magnetization Jc for DCAT specimens displayed a weak link character maintaining <1000A/cm2 at 77K and 1.0T as compared to <100A/cm2 for the other MPMG specimens. Lower 211 weight fractions in the DCAT samples compared to MPMG samples indicated other pinning sites were active in addition to 211-YBCO interfacial sites. |
