INFLUENCE OF OXYGEN-CONTENT AND STRUCTURAL DEFECTS ON LOW-TEMPERATUREMECHANICAL-PROPERTIES OF HIGH-TEMPERATURE SUPERCONDUCTING SINGLE-CRYSTALS AND CERAMICS

The data for the microhardness and fracture toughness of Y-Ba-Cu-O and Bi-based single crystals and ceramics in the temperature range 77-293 K are presented and analyzed. Our study reveals that the microhardnes s of high temperature superconductors is very sensitive to the oxygen stoichiometry, the phase composition, the temperature, and to the micr ostructural defects such as impurities, intergranular boundaries, and voids. Attention is drawn to the anisotropy of the micromechanical pro perties and to the features of the fracture in the vicinity of the ind entation. The data available on the plasticity of Y-Ba-Cu-O and Bi-Sr- Ca-Cu-O from micro-and macrotests are compared. (C) 1997 American Inst itute of Physics.