YBCO thick films on MF2 (M=Mg, Ca, Sr, Ba) substrates

YBCO thick films were prepared on single-crystal substrates of the fluoride-based compounds MF2 (M Mg, Ca, Sr, Ba) using a simple, screen printing method. The film formed on BaF2, which was heated at 900 degrees C for 60 min in an argon atmosphere and then exposed to oxygen, showed a relatively high Jc value of 680 A cm-2 at 77 K in zero magnetic field. This Jc value is almost the same as that of YBCO films on a YSZ substrate. Impurity phases such as BaF2 were, however, produced in the film due to the film-substrate interactions, which reduced the Jc of the sample. For an SrF2, substrate, the films showed zero resistance at 78-89 K, but its Jc value was less than 10 A cm-2. In the case of MgF2 and CaF2 substrates, fairly large amounts of Mg, Ga, and F were found to be present in the films, which destroyed the superconducting properties of the films. (author)