Electrical characterization of thick film superconductors

Abstract

With the recent discovery of High T_c ceramic superconducting materials, many potential applications which were considered impossible just a few years ago are now being realized. These new uses of superconductors will take place in electronics and energy systems where many different materials are used together. If these superconducting materials are to be used successfully, they must be characterized.

Film quality was characterized by measuring the electrical properties under different conditions. Films were tested on alumina and magnesia substrates, to characterize the substrate interactions. Films were printed in different thicknesses and different widths, to determine the effect of film geometry on film quality. Finally these films were aged in a room ambient to determine the effect of atmospheric exposure.

The results of these tests show that thick film Superconductors can be easily fabricated on magnesia substrates. Superconducting thick films can also be fabricated on alumina substrates, provided the film thickness is greater than 100μm and line width is greater than 50 mils. On either substrate material, critical currents of the films consistently decreased with thinner, narrower lines and environmental exposure. The maximum critical current on 2 magnesia substrates was 635 A/cm² for an unaged 77μm thick by 200 mil wide line, and the minimum was 345 A/cm² for a 25μm thick by 50 mil wide line aged for thirty days. Alumina substrates showed the same trend with a maximum of 75 A/cm² for an unaged 125μm thick by 200 mil wide line and a minimum of 47 A/cm² for a 100μm thick by 100 mil wide line aged for thirty days.