Processing - property relations for Ba2YCu3O7-x high Tc superconductors

Ceramic materials exhibit strong relationships between their physical properties, their ceramic microstructures, and the processing sequence that produced these microstructures and properties. This interrelation between processing, microstructures, and properties is particularly true for the new high Tc superconducting ceramic oxides of the type Ba2YCu3O7-x. To characterize some of these relations, a number of properties have been measured for these superconducting ceramics, and related to the microstructures and processing sequence. The Ba2YCu3O7-x ceramics were prepared by powder processing techniques, followed by dry pressing and sintering. Sintering was conducted in both air and flowing oxygen at various temperatures, followed by annealing at various temperatures and environments. Superconducting properties, such as the transition temperature and the width of the transition, were measured by both electrical conductivity and AC magnetic susceptibility; both showing a strong sensitivity to annealing temperature and annealing atmosphere. The microstructure and density was also strongly dependent on processing conditions. In this regard compositional mapping proved to be an important technique for quantifying the microstructural properties. Structural properties, which will be important for the reliable use of the materials, were characterized through the fracture strength, the fracture toughness, and the elastic moduli