Synthesis and incorporation of nanosized pinning centers for YBa2Cu3O7-x superconductors

The solution processing of YBa2Cu3O7-x (YBCO) coated conductors has been extensively studied, however the dependence of Jc on the magnitude and the orientation of the magnetic field still poses problems for practical applications in high magnetic fields. This can be circumvented by the incorporation of inert metal oxide nanoparticles in the YBCO coating. In-situ created nanostructures present in the YBCO layer have proven their effectiveness. In these nanocomposites the nanostructures tend to attain random orientation with respect to the epitaxial YBCO, generating incoherent interfaces within the epitaxial YBCO matrix that causes localized nanostrained regions, that has been correlated with a strong enhancement of vortex pinning.[1] However, the size, morphology and distribution of in-situ created nanostructures an thus the associated nanostrain cannot be controlled in the layer. The less established ex-situ approach, in which first nanoparticles are synthesized by wet chemical methods and are afterwards added to the YBCO precursor solution, offer the promise of a better control over particle growth, size, size distribution and shape and thus also over the introduced nanostrain.This research is devoted to the processing of ZrO2 and HfO2 nanocrystals (NCs), useful for ex-situ pinning in YBCO. We explored a microwave-assisted solvothermal and a heating-up synthesis method for the preparation of the NCs.[2] Both synthesis methods give rise to small NCs (3 – 10 nm in diameter) and narrow size distributions, characterized by means of XRD, DLS and TEM analyses. The two methods lead to NCs with different surface chemistry, yet in both cases the NCs are capped with organic ligands to prevent agglomeration, ensuring colloidal stability in apolar solvents.[3] However, as the YBCO precursor typically provides a more polar environment, e.g. methanol, an important aspect of this research involves finding the appropriate stabilizing molecule and studying the particle stability in the polar YBCO precursor solution. After ensured particle stability in the YBCO precursor solution, the YBCO-NCs suspension were deposited on a La2Zr2O7 substrate through spin coating to study the influence of the NCs in the YBCO coating. The effect of different concentrations of APCs in YBCO were investigated, bringing us closer to the effective incorporation of high-temperature superconductors in high and alternating magnetic field applications, relevant in alternative energy generation.References[1] X. Obradors, T. Puig, A. Palau, et al. (2011) Comprehensive Nanoscience and Technology 303-349[2] J. De Roo, K. De Keukeleere, J. Feys et al. (2013) Journal of Nanoparticle Research 15:1778[3] J. De Roo, F. Van den Broeck, K. De Keukeleere, et al. (2014) JACS 9650-9657The solution processing of YBa2Cu3O7-x (YBCO) coated conductors has been extensively studied, however the dependence of Jc on the magnitude and the orientation of the magnetic field still poses problems for practical applications in high magnetic fields. This can be circumvented by the incorporation of inert metal oxide nanoparticles in the YBCO coating. In-situ created nanostructures present in the YBCO layer have proven their effectiveness. In these nanocomposites the nanostructures tend to attain random orientation with respect to the epitaxial YBCO, generating incoherent interfaces within the epitaxial YBCO matrix that causes localized nanostrained regions, that has been correlated with a strong enhancement of vortex pinning.[1] However, the size, morphology and distribution of in-situ created nanostructures an thus the associated nanostrain cannot be controlled in the layer. The less established ex-situ approach, in which first nanoparticles are synthesized by wet chemical methods and are afterwards added to the YBCO precursor solution, offer the promise of a better control over particle growth, size, size distribution and shape and thus also over the introduced nanostrain.This research is devoted to the processing of ZrO2 and HfO2 nanocrystals (NCs), useful for ex-situ pinning in YBCO. We explored a microwave-assisted solvothermal and a heating-up synthesis method for the preparation of the NCs.[2] Both synthesis methods give rise to small NCs (3 – 10 nm in diameter) and narrow size distributions, characterized by means of XRD, DLS and TEM analyses. The two methods lead to NCs with different surface chemistry, yet in both cases the NCs are capped with organic ligands to prevent agglomeration, ensuring colloidal stability in apolar solvents.[3] However, as the YBCO precursor typically provides a more polar environment, e.g. methanol, an important aspect of this research involves finding the appropriate stabilizing molecule and studying the particle stability in the polar YBCO precursor solution. After ensured particle stability in the YBCO precursor solution, the YBCO-NCs suspension were deposited on a La2Zr2O7 substrate through spin coating to study the influence of the NCs in the YBCO coating. The effect of different concentrations of APCs in YBCO were investigated, bringing us closer to the effective incorporation of high-temperature superconductors in high and alternating magnetic field applications, relevant in alternative energy generation.References[1] X. Obradors, T. Puig, A. Palau, et al. (2011) Comprehensive Nanoscience and Technology 303-349[2] J. De Roo, K. De Keukeleere, J. Feys et al. (2013) Journal of Nanoparticle Research 15:1778[3] J. De Roo, F. Van den Broeck, K. De Keukeleere, et al. (2014) JACS 9650-9657C