AC susceptibility measurements on directionally solidified YBCO samples

Measurements of chi' and chi '' have been performed on directionally solidified YBCO 211 doped samples. We analyze the variations of structural and superconducting properties as a function of a relevant fabrication parameter such as the pulling rate within a region with fixed thermal gradient. Measurements are made at different AC magnetic field and frequencies. The effects of intra- and inter-domain screening currents are compared among samples with different superconducting properties. Although the XRD shows quasi-single crystal behaviour, residual granular-like effects are observed. However, in good quality samples the dissipation due to the inter-domains coupling is orders of magnitude lower than the dissipation in sintered specimens.