The fluorine-free metal-organic decomposition (FF-MOD) route is one of the table-top methods for the growth of high-quality superconducting YBa2Cu3O7-δ (YBCO) films due to its advantages of being environmentally friendly and having a faster film deposition rate. However, the nucleation and growth mechanism originated during this process are not yet comprehensively understood. In this paper, the microstructural characteristics of YBCO films quenched from different growth stages were investigated, upon which a complete nucleation and growth model is established. A micro-Raman and scanning electron microscopy (SEM) coordinated study demonstrates the coexistence of polycrystalline and epitaxial grains at the early stage of nucleation. Combined analysis of transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS) indicates that YBCO epitaxial nucleates by following the Volmer-Weber growth mode. We observed that as the growth process proceeds, the nuclei at the interface have a significant growth advantage over those in the body, thus leading to coalescence of island epitaxial grains via consuming neighboring polycrystalline grains and intermediate phases. Moreover, by establishing a kinetic phase diagram of YBCO film growth, we also found that the optimal process conditions are mainly related to the enhanced transient liquid phase and BaCeO3, which are somehow associated with the cross-linkage between the sintering temperature, dwell time, and oxygen partial pressure (pO2) of the sintering atmosphere. Remarkably, a high critical current density (Jc) value of 3.6 MA/cm2 (77 K, self-field) was obtained in the YBCO film grown on the CeO2 capped technical substrate deposited under optimized conditions, which is rather comparable with that on the LaAlO3 single crystal. The angular-dependent Jc analysis revealed that the anisotropy of the YBCO film is reduced to 3, as estimated by the Blatter scaling approach, which is much smaller than that of the typical defect-free pristine films. This work improves understanding of the nucleation and growth mechanism in the YBCO film deposited on the CeO2-buffered technical substrate and facilitates the industrialization development of epitaxial oxide films with superior performance in the future.
|Original language||English (US)|
|Number of pages||11|
|Journal||Crystal Growth and Design|
|State||Published - Jan 1 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors would like to acknowledge the financial support from National Natural Science Foundation of China No.51502171),Instrument Analysis Center of Shanghai Jiao Tong University for performing RISE and PPMS, and Center for Advanced Electronic Materials and Devices (AEMD) for performing SEM.