INDENTATION-INDUCED DEFORMATION AND MICROCRACKING OF HIGHLY TEXTURED SUPERCONDUCTING (BI,PB)(2)SR2CA2CU3OX CERAMIC

A high T-c ceramic superconductor has been prepared having a high degr ee of preferred orientation, this having been generated by means of a large magnetic field during the early stages of processing. The textur e of the material has been characterized using XRD textural analysis a nd the microstructure by high resolution electron microscopy. Pyramida l indentation (Vickers indent), deformation, and cracking have been in vestigated using high resolution SEM. Semispherical deformation zones were formed under indents, a result of slipping of adjacent ab/ab (bas al) plane grain boundaries and some microcrack development, together w ith lattice deformation on the basal plane. Densification of the green compact was also observed in the deformation zones, where lateral cra cking has been seen to take place along the ab/ab plane grain boundari es, Radial cracking has been seen to take place along the low angle gr ain boundaries of the lattice ab/ab plane when indentations were made on the surface perpendicular to the preferred texture surface of the m aterials and also at the highly deformed corners of indent diagonals. The stresses generated resulted in the fracture of the flake-shaped gr ains and initiated small. radial cracks. The Vickers microhardness of the textured ceramics was found to decrease with increasing load.