Fabrication, Characterization and Study of MOD Multi-Layer YBCO Films

Fabrication of thick YBa₂Cu₃O_y (YBCO) films with high critical current densities(J_c) has remained one of the major challenges in the coated conductor development process. In this work, we report successful fabrication of several multi-layer YBCO films with thicknesses ranging from 0.1 micrometers to 1.2 micrometers. The films were deposited on a single crystal substrate by using a multi-layer TFA-MOD technique. The effect of variation in the thickness of an individual layer in a multi-layer film on the overall properties of the film was studied by processing multi-layer films with individual layers of 0.1 micrometers, 0.2 micrometers and 0.5 micrometers. The J_c value for the 0.1 micrometers thick single-layer film was as high as 7 MA/cm², and the J_c for 6-layer1.2 micrometers thick film was 1 MA/cm² at 77 K and self field. XRD, SEM and TEM were used to study the dependence of J_c on the orientation, texture and microstructure of the film. It was found that the texture, connections between the two successive layers, porosity, and the crack formation affect the J_c of the film. In addition, we report a multi layer fabrication route with a shorter duration of the pyrolysis reaction according to the number of coats.