Tailoring Microstructures of High-Tc Superconducting Films

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This project strives for greater understanding of microscopic mechanisms of cation exchange and a new process, PONSE (Pores by nanoscale strain engineering). These processes hold promise for engineering microstructures and physical properties of several high-Tc superconductor (HTS) films including YBa2Cu3O7 (YBCO), Tl-based (Tl-HTS) and Hg-based (Hg-HTS) superconductors. Three sub-topics will be investigated: 1) epitaxy of Hg- HTS films using the cation exchange process. The reversibility of cation exchange between Tl-HTSs and Hg-HTSs is aimed at understanding the cation exchange mechanism and application of the process for improving microstructures of Hg-HTS films via alloying Hg-HTS and Tl-HTS and adding nano-pins on the lattice. 2) systematic study of vicinal growth of Tl-HTS and Hg-HTS films, with focus on nucleation via anti-phase grain boundary formation, microstructure evolution and microstructure variation during cation exchange from Tl-HTS to Hg-HTS films. A quantitative correlation between microstructure/defects and magnetic pinning will be investigated specifically through measurement of critical current density (Jc) as function of temperature, magnetic field and the orientation of the magnetic field. 3) studies of porous YBCO films obtained via the PONSE process through vicinal growth and nanoparticle insertion. The significant improvement in the Jc of these .superconductor sponges. raises questions on both material science and material physics of the porous superconductors. To answer these questions, the mechanism of pore formation will be investigated for greater understanding and achievement of precise control of pore dimension, density, shape and distribution. The superconducting properties of the porous YBCO films will be studied to understand the role of pores and reduced dimension on superconductivity. The studies of material science and material physics will be carried out in a coherent fashion. The goal is to achieve greater understanding and high performance YBCO films with desired microstructures and superconducting properties. *** The project addresses fundamental materials research with strong technological relevance to electronics and photonics, and effectively integrates research and education. The impact of the project includes education of the next generation of scientists in nanoscience and material science/physics with active PI emphasis on broadening participation of underrepresented groups.