Superconductivity of YBCO Thick Films Prepared by Spark Plasma Sintering

YBa 2 Cu 3 O x (YBCO) superconducting thick films have been fabricated on Cu substrates, using a simple screen-printing method from Cu-free powders (Y 2 O 3 and BaCO 3 ). However, such films have poor superconducting properties such as critical current density ( J c ) due to the low film density. In this work, we investigate the effect of uniaxial c -axis pressure on the superconducting properties of these YBCO films using a spark plasma sintering (SPS) technique. The film screen-printed on Cu substrates was heat-treated at 850°C for 5 min in vacuum varying the pressure (15, 30, and 45 MPa). To form a superconducting YBCO phase, the film was reheat-treated at 930°C for 30 s in air followed by oxygen annealing at 450°C for 1 h. For heat-treatments performed under pressure, lower film porosity was obtained, and a higher crack density was also observed compared to films prepared without pressure. The densification of the YBCO thick films using the SPS technique was very effective in improving the superconducting properties of the films.