Nucleation and growth of YBa2Cu3O7− thick films processed on YSZ, Al2O3, MgO and BaZrO3 substrates

Abstract

The substrate material in the processing of superconducting thick films not only performs an important role in supporting the film but is also seen to be a significant factor in the microstructural development of the film. The characterisation of YBa2Cu3O7−x (YBCO) thick films melt processed on a variety of substrate materials (e.g., YSZ, MgO, Al2O3, BaZrO3) revealed a wide variation in the microstructures and properties obtained. The microstructures of melt-processed YBCO films on yttria-stabilised zirconia (YSZ) substrates display a characteristic morphology described to be “spherulitic” or “hub and spoke”. Melt processed films displaying this morphology have been shown to exhibit desirable superconducting properties for potential applications in the electronics and microwave component industries. The nucleation and growth of such microstructures has been investigated and is described, together with methods of manipulating the nucleation sites and further improving the superconducting properties obtained in films.