Compositional variations in the bulk of YBa₂Cu₃O_x thick films

Abstract

Thick films of YBa₂Cu₃O_x (123) prepared on a number of substrate materials, namely Si, Al₂O₃, SrTiO₃, MgO and YSZ, have been investigated for the compositional variations/impurity phases present, microstructure, grain orientation etc. Energy-dispersive X-ray and X-ray diffraction analyses for as-prepared films of two different thicknesses, 2–3 μm and 10–15 μm, and after their partial and complete etching, are reported. The results show that the film-substrate reaction dominates up to ∼2–3 μm thickness of a film. The decomposition of 123 material at the processing temperature and the substrate-film reaction together are seen to govern the crystallization behaviour, compositional variations and the superconducting properties of the films. In various cases, the films have been found to undergo superconducting phase transitions at temperatures between 66 and 89.5 K.