Sol-gel Tb₂O₃ buffer layers on Ni tapes for YBCO coated conductors

In this study, processing of Tb₂O₃ buffer layers on textured Ni tapes were evaluated for YBa₂Cu₃O_7-x (YBCO) coated conductor. A solution deposition process was used to grow textured Tb₂O₃ buffer layers on the Ni tapes. The solution was prepared using Tb-2, 4-pentanedionate precursor, methanol as solvent, chelating agents and a solution modifying chemical, triethanolamine (TEA). Biaxially textured Ni substrates were dipped into the solution by a reel-to-reel sol-gel dip coating system. The amorphous thin films were dried at 300°C for 30 sec and then heat-treated at 500°C for 2 min in air using an in-line three-zone furnace. The films were annealed at temperature range of 900°C and 1170°C for 10 to 20 min under 4%H₂-Ar gas flow. The textured buffer layers were obtained using TEA onto the textured Ni tapes at 1150°C for 10 minutes. The Tb₂O₃ (222) pole figure revealed a single cube-on-cube texture. The omega and phi scans indicated good out-of-plane and in-plane orientations. DTA results pointed out that Tb based gel film transformed to oxide structure at temperature range of 350°C and 410°C. Microstructures of the Tb₂O₃ films were investigated by Environmental Scanning Electron Microscope (ESEM), and the films were dense, smooth and free from cracks and pinholes.