Microstructure and superconductivity in YBa2Cu3O7-x ceramics deformed at high temperatures: I. Microstructural considerations

The effect of extrusive deformation at 875 degrees C on the microstructure of YBa2Cu3O7-x ceramics has been studied by optical metallography, transmission electron microscopy (TEM), X-ray structural and texture analysis. Dynamic recrystallization developing under deformation transforms the initial coarse-grained plate-like microstructure into a fine-grained equiaxial one with grain size less than 0.1 mu m. A mechanism is proposed for this transformation. An analysis of pole figures has shown that a radial (001) texture is formed during extrusion. Under increasing strain the homogeneity of the microstructure is enhanced, and the texture becomes more pronounced and sharp.