CONTROL OF GRAIN ALIGNMENT TO FABRICATE LONG Y-BA-CU-O SUPERCONDUCTORS WITH HIGH-CURRENT DENSITY

A directional solidification method has been developed to grow YBa2Cu3Ox samples in excess of 55 mm in length with uniform grain alignment and a-b planes oriented parallel to the sample length. Using a furnace configuration that yields a negative lateral gradient, the YBa2Cu3Ox grains have been forced to nucleate and grow along the axis instead of at an angle to the sample length. X-ray pole figures analyses along the entire length at different sections show that the a-b planes are aligned parallel to the sample length with deviations less than 5-degrees along the growth direction. Transport critical current density (J(c)) measurements over the entire length and at different sections of the sample reveal a uniform current density in excess of 7000 A/cm2 at 1.5 T and 77 K.