Influence of Microstructure on Superconducting Properties of YBa₂Cu₃O_7−δ Studied by Means of AC‐Susceptibility

Using an ac susceptibility technique the superconducting properties of sintered YBa₂Cu₃O_7−δ samples are studied. A strong systematic influence of unaxial pressure applied during the preparation step of the pellets on the superconducting properties is found, whereas all samples have the same density and oxygen content. The width of the junctions between the grains is found to be growing with higher pressure. In this paper also the advantages are demonstrated of ac‐susceptibility measurements in determining effects of the microstructure on the sample properties and of the contactless measurement of the critical current, J_c, over a wide temperature range.