Speaker
Description
It is discovered heredity in physical properties in HTSC-thick films after processing HTSC-powders by method of the electromagnetic separation (EMS) . The method was developed for EMS HTSC-powdered superconductors suspended in liquid nitrogen in alternating magnetic field.[1] In the thick film deposition process HTSC is simply heated and "painted" on to the substrate and then fired in a furnace. The main reason for critical current degradation in bulk high-T samples is the grain boundaries, impurities, ballast-phases, and structural defects. Unfortunately, even the most advanced techniques commercially available are unable to produce homogeneous HTSC powders. The EMS-method allows statistical improvement in the uniformity of HTSC powders by decreasing the quantity of defective zones in the separated powders, the number of non-valid phases, admixtures and thus to increase the Tc, Icr (critical current).At the same time, ∆TC- (width of the SC-transition) is being decreased. After separation of the HTSC- powders the concentrate has been saturated with oxygen and is receiving superconductivity. This is in contrast to the tail fraction of the YBa2Cu3Ox powders, which exhibits the tetragonal structure (x < 6.5%) and shows an absence of a superconducting transition throughout the entire temperature interval. Three YBa2Cu3Ox -thick-films by the paint method on the MgO substrate from the source material, the separated high-quality concentrate, and the low-quality remnant (tail) had been produced. The films exhibit different structural and electrical properties, in particular: Icr, and ∆Tc. For example, in the films YBa2Cu3Ox, that was made from the high-quality concentrate ∆Tc- the width of the HTSC-transition, is decreased from 5-7 K to 1-2K.
Reference:
1. E.L. Broide, Method of Separating a Superconducting Fraction From a Mixture, US Patent 5,919,737, Ju1,6 ,1999
