Key Microstructural Features of MOD YBa2Cu3O7−∂ Films on Textured Nickel Substrates

Key features of the microstructure in high critical current density (J_C ) MOD Y₁Ba₂Cu₃O_y (YBCO) films on biaxially-textured nickel substrates with intervening buffer layers are presented. 0.8 mum thick MOD YBCO films on the 4cm wide RABiTS templates have 77K, self-field J_C and I_C values exceeding 3 MA/cm² and 250A/cm-width, respectively. MOD YBCO films have a laminar grain structure with a high density of YBa₂Cu₄O_y(Y124) intergrowths, which give rise to an enhanced peak in angular anisotropy measurements of J_C when the applied field is parallel to the ab planes of the YBCO films. Other key aspects of MOD YBCO films related to the laminar growth mode and layered microstructure are grain boundary overgrowth, grain boundary meandering, colony microstructures, incoherent precipitates of Y₂O₃ and Y₂Cu₂O₅, and phase separations.