Microstructure and superconducting Behavior of YBa2Cu3O7-delta films fabricated from colloids of nanoparticles
A new approach in the synthesis of YBa2Cu3O7-delta (YBCO) films has been demonstrated, which uses a colloidal dispersion of nanoparticles of Y-Ba-Cu-O as precursor. Since nanoscale particles tend to be very reactive, this precursor allows rapid processing. Moreover, since the starting composition is very similar to the final film, gaseous reaction products that cause porosity and toxicity in other methods can be minimized. This paper compares the microstructure and superconducting behavior of films prepared from nanoparticle suspensions to those fabricated by metal-organic deposition technique using trifluoroacetates. It is seen that these films show significantly reduced porosity and some enhancement in self-field critical current density (J(c)). The enhancement of J(c) is more significant in high magnetic fields, probably due to the nanoscale precipitates spontaneously formed. It also appears that there is scope of improving this further by adding small amounts of CeO2 nanoparticles in the precursor. However adding larger amounts may have a detrimental effect. Additional investigation on the role of nano-inclusions in flux pinning will be needed, but this work clearly shows that the use of nanoparticle colloids for making YBCO films is a very promising approach that will be scalable, non-toxic, and allow easy introduction of flux-pinning defects.