Use of the Meissner effect to separate, purify, and classify superconducting powders

A separation technique, based on the Meissner effect, to purify and classify superconducting powders was developed. Powders of the Y1Ba2Cu3O7−x composition were sealed in a glass tube, cooled to liquid-nitrogen temperature, and passed over the pole of a magnet. The superconducting phase responded to the field and moved away from the magnet, whereas the nonsuperconducting phases, impurities, especially magnetic, and unreacted phases did not move. X-ray diffraction revealed that the separated powder was single phase with all impurity phases eliminated. Furthermore, the powder particles separated along the length of the tube according to their size and applied magnetic field: the larger the particles and/or the field the farther the movement and the smaller the particles that moved.