Magnetic Properties of YBCO Single-Crystal Grown on Y2O3 Layer by a Cold Top-Seeding Method

In this work, single-crystal samples 20 mm in diameter were grown by a cold top-seeding method. In order to study the effect of an Y2O3 buffer layer, a compacted precursor was located in a crucible on a buffer layer of freely poured Y2O3 powder. The YBCO bulk samples were carefully prepared in the same chemical composition. In order to examine the homogeneity of the samples, rectangular specimens were cut from a sample. The structural orientation of the specimens was measured by a X-ray diffractrometer (XRD). The microstructure was observed with a Scanning Electron Microscope (SEM). The magnetic properties were measured using a Vibrating Sample Magnetometer (VSM) at 77 K with the applied magnetic field parallel to the c-axis. As a result only (00l) peaks were observed in X-ray diffraction data, indicating that all specimens are highly oriented with the c-axis perpendicular to the top surface. Also the cut samples exhibited very fine Y211 inclusion distributed in the bulk sample observed in SEM micrographs. The critical current density J (c) (A/cm(2)) has been estimated by the extended Bean model. The maximum value of the critical current density at 77 K is 5.2x10(4) A/cm(2) in a self-field. The trapped magnetic field measurements of the samples were performed by using Hall probe scanning device with static field of 0.5 T at 77 K. The single-domain sample exhibits a trapped field of 1140 G at 77 K.