Densification and Shear Deformation in YBa 2 Cu 3 O 6+δ Powder Compacts

Powder compacts having a nominal composition of YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} were sintered in air between 910{degree} to 940{degree}C in a loading dilatometer that permitted the application of small, controlled uniaxial stresses to the sintering compact. The highest density (95% of theoretical) was obtained after sintering without load for {approx} 2 h at 935{degree}C. The application of constant, small uniaxial stresses produced extensive shear deformation and a small increase in the densification rate. The measured ratio of the densification rate to the creep rate provided strong support for the presence of a liquid phase during sintering. The data allowed the measurement of the ratio of the creep viscosity to the densification viscosity, which was {approx} 0.8 over the density range 0.6 to 0.8, and the sintering stress, which was {approx} 0.8 over the density range 0.6 to 0.8, and the sintering stress, which was {approx} 400 kPa. These data show that extensive shear deformation and small but measurable increases in the densification rates may be achieved by the application of relatively small uniaxial stresses ({approx} 1 MPa) during sintering of YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} powder compacts.