Direct Observation of Wrinkling and Healing Evolution for YBa2Cu3O 7−δ Precursor Films Prepared by the Metalorganic Solution Method

Surface morphology evolution of the trifluoroacetate metal-organic precursor for YBa2Cu3O 7−δ during pyrolysis was observed by in situ optical microscopy, and a mechanism was proposed based on an analogy to the gel-swelling-induced surface instability. The cracking and wrinkling phenomena were ascribed to the competition between reaction and diffusion. The critical condition for wrinkling was obtained, and the dependence between the heating ramp and the surface morphology was identified. Experiments showed that three types of cracks existed, and one of them exhibited healing behavior during drying. The wrinkles may exhibit healing behavior as well under certain condition. These results are believed to arise from the suppression of the precursor surface instability during pyrolysis treatment, which is relevant to the manufacturing of the coated conductor.