Characterization of the texturing of YBa 2 Cu 3 O 7−σ in the presence of liquid phase additives

Grain growth and texturing of YBa2Cu3O7−δ is greatly influenced by the presence of liquid phase additives during sintering. Oxides such as TiO2, SiO2, Bi2O3, and Pr6O11 were incorporated into the liquid phase during the sintering of YBa2Cu3O7−δ (123) by use of grain boundary diffusion couples and the microstructure was analyzed using scanning electron microscopy/electron dispersive spectroscopy. Exaggerated grain growth and domain formation was observed in bulk specimens. Differential thermal analysis and real time dynamic x-ray diffraction were used to determine reaction sequencing. The ability and extent of domain formation was determined for 123 samples coupled with impurity oxides to be a function of sintering temperature (940–980°) and oxygen partial pressure. Enhanced texturing was observed at low PO2 atmospheres. The addition of Bi2O3 and TiO2 was shown to degrade dc magnetic susceptibility of 123 whereas SiO2 and Pr6O11 enhanced it. The domain formation and texturing takes place in the bulk for 123 at temperatures of 980°C or below (i.e. well below the peritectic decomposition temperature) by the interaction of an impurity doped liquid phase followed by a precipitation and exaggerated grain growth.