The hardness and Young's modulus of bulk YBa2Cu3O7−x (1:2:3) and YBa2Cu4O8 (1:2:4) as determined by ultra low load indentation

Abstract

Using a highly-spatially-resolved mechanical properties microprobe, the Young's modulus and hardness of bulk YBa₂Cu₃O_7−x (1:2:3) and YBa₂Cu₄O₈ (1:2:4) have been determined. The Young's modulus of a superconductor is an important parameter in determining critical grain sizes above which microcracking will occur due to anisotropic thermal stresses that arise during processing. This phenomenon of microcracking has been determined to cause a decrease in the attainable critical current densities in bulk superconductors. The mechanical properties data for these two materials show that the Young's modulus of 1:2:3 is approximately 35% greater than the modulus of 1:2:4. This along with available anisotropic thermal expansion data for 1:2:3 and 1:2:4 suggests that the critical grain size for 1:2:4 is about 7 times greater than the critical grain size for microcracking in 1:2:3.