AC SUSCEPTIBILITY MEASUREMENTS ON DIRECTIONALLY SOLIDIFIED YBCO SAMPLES

Measurements of chi' and chi '' have been performed on directionally s olidified YBCO 211 doped samples. We analyze the variations of structu ral and superconducting properties as a function of a relevant fabrica tion parameter such as the pulling rate within a region with fixed the rmal gradient. Measurements are made at different AC magnetic field an d frequencies. The effects of intra- and inter-domain screening curren ts are compared among samples with different superconducting propertie s. Although the XRD shows quasi-single crystal behaviour, residual gra nular-like effects are observed. However, in good quality samples the dissipation due to the inter-domains coupling is orders of magnitude l ower than the dissipation in sintered specimens.