ENHANCED LEVITATION PROPERTIES IN MELT-TEXTURED YBCO SAMPLES GROWN WITHOUT TEMPERATURE-GRADIENT

We investigated different techniques for magnetic-levitation property enhancement of the melt-textured YBCO sample grown without temperature gradient. No improvement in microstructural properties could be achie ved by increasing the excess Y-211 phase percentage above 20% (molar) or by adding a few weight percent of Ag. Large grain dimensions (up to 20 mm) were reached in samples undergoing both a presintering treatme nt at 950 degrees C and a stage of several hours at 1000 degrees C dur ing the growth slow-cooling phase. The obtained samples are characteri zed at 77 K by a levitation force of 26.9 N and a magnetic critical cu rrent density up to 10(4) A/cm(2) at 1 T. Furthermore a single-grain s ample could be obtained placing a Nd2O3 powder seed onto the sample su rface.