Nov 8, 2012
Randomly orientated nanoparticles play key role in superconducting composite film
High current superconducting tapes have emerged as a new opportunity to enable broad penetration of high-temperature superconductors in applications such as power systems and high-performance magnets. These conductors, which are already commercially available, consist of a multilayered oxide structure generated on top of a flexible metal substrate. Predictions state that these superconducting tapes will replace copper conductors, but there is still considerable room for improvement in performance and cost. Recently, outstanding results have been shown when oxide nanoparticles were introduced into the superconducting matrix.
Earlier this year, researchers from the Superconducting Materials and Large Scale Nanostructuration Group based at the Institute of Materials Science of Barcelona (ICMAB-CSIC), Spain, in collaboration with researchers from France, Belgium, Israel and the US, proposed in Nature Materials that this response is associated with the generation of atomic-level strain in nanoregions within the superconducting matrix. Despite the challenges involved, there is a strong need to widely explore the immense capabilities associated with these new types of superconducting nanocomposite materials and to implement them cost effectively in long-length conductor processes.
Now, researchers have struck at the heart of this issue by performing a thorough study of the particular case of YBa2Cu3O7 nanocomposite thin films with spontaneous segregated ternary oxide nanoparticles formed by a low-cost and scalable chemical solution deposition technique. Reporting their results in the journal Superconductor Science and Technology, the scientists have examined the material in detail, including the orientation of the nanosized particles, the type of shared interface with the superconductor, and the strain generated within the matrix identified from scanning transmission electron microscopy and advanced X-ray diffraction analysis. These aspects are then correlated with the superconducting properties of the sample.
The nanocomposites are unique because the nanoparticles segregated within the superconducting matrix are mainly randomly orientated. In fact, the samples show the highest percentage of randomly oriented nanoparticles within the YBCO matrix ever reported. This is essential considering that this parameter promotes a YBCO defect-rich microstructure (Cu-O intergrowths) and consequently generates highly strained nano areas that ultimately lead to superconducting properties three times higher than the pristine film.
This study has been crucial to underline the universal and distinct behaviour of chemical solution deposited superconducting nanocomposite films with embedded nanosized oxide second phases compared with the analogous vacuum deposited films. The work paves the way towards isotropic high-current conductors at high magnetic fields and high temperatures.
Full details can be found in the journal Superconductor Science and Technology.
About the author
Mariona Coll is a member of the superconducting materials group at the Institut de Ciència de Materials de Barcelona (ICMAB-CSIC).