Effects of Processing Variables on the Y_2BaCuO_5 Size and Magnetic Properties of Melt-Processed YBa_2Cu_3O_x

摘要

Samples of YBa_2Cu_3O_x (123) with excess Y_2BaCuO_5 (211) in the molar ratio of 5:1 (123/211) were processed using the "solid liquid melt growth" (SLMG) technique. The effect of hold time above the peritectic on the magnetic properties was examined. Extended hold times above the peritectic during processing degrade the magnetic properties of SLMG processed 123. In SLMG 123, the very fine ( < 100 nm) 211 particles produced by this processing route are the primary magnetic flux pinners. Extended hold periods reduce the number and/or coarsen the average size of these fine precipitates, resulting in a reduced magnetization. These results were compared to undoped Y123 processed by the more traditional melt texture growth (MTG). In MTG processing, extended hold times above the peritectic are found to result in improved magnetic behavior because of increased defect densities.