Development of rare earth niobate buffer layer for YBCO coated conductor using chemical solution deposition approach

We have grown epitaxial rare earth niobate (RE₃NbO₇; RE - La, Ce, Nd, Sm, Eu, Gd, Ho, Y, and Yb) buffer layers on biaxially textured Ni-W substrates using chemical solution deposition approach. Precursor solutions of 0.4 M total cation concentration were spin coated on short samples of Ni-3 at.%W (Ni-W) substrates and heat-treated at 1050 to 1100°C in a gas mixture of Ar-4%H₂ for 15 minutes. Effect of solution chemistry and processing atmosphere on texture and microstructure were studied. Detailed X-Ray studies indicated that all the rare earth niobates were grown epitaxially. There was no significant change observed in texture for different precursor chemistry, however, dramatic effect on surface morphology observed. SEM and AFM investigations of RE₃NbO₇ films reveal noticeable difference in surface morphology and roughness for various processing atmospheres. Processing under a 20% wet Ar-4% H₂ gas mixture was found to be the optimum condition for growing Gd₃NbO₇ films with high quality microstructure.