Interfacial Effects and Superconductivity in High-Tcmaterials

A series of quasihomogeneous superconducting powders of YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/ have been prepared by sieving and characterized by electron microscopy and x-ray diffraction. Quantitative size-dependent and temperature-dependent magnetic levitation and susceptibility measurements of random powders and of field-oriented (at T