Microstructural and electrical characterization of bulk YBa 2Cu 3O 7− δ ceramics

Abstract

The value of critical current density at 77 K in “zero” applied field ( J c) characterizing the superconducting state for YBa 2Cu 3O 7− δ ceramics is closely related to the microstructure. The interrelationships between the microstructural factors such as pore volume fraction, oxygen content, average grain size, are complex. However, these factors also influence the normal state resistivity measured at room temperature ( ρ 300). We demonstrate how the current carrying cross section influences Jc and ρ 300 in a similar way. Data, reported for two classes of YBa 2Cu 3O 7− δ : small grain porous ceramics and larger-grain denser ceramics, reveal an approximate linear relation between ρ 300 K and J c. Extrapolation of this relation to a fully dense small grain YBa 2Cu 3O 7− δ ceramic yields values of ρ 300 = 0.4 mΩ cm and J c = 10 3 A cm −2.