Probing and manipulating strained interfaces with oxide superconductors

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Superconductors are capable of carrying electric current without loss, one of the most exotic physical phenomena in nature. This capability is described quantitatively by critical current density Jc, superconductivity. Enhanced Jc will provide powerful new opportunities for restoring the reliability of the power grid and increasing both its capacity and efficiency, regarded as an engineering grand challenge. As energy demands increase and our existing grid ages, the USA will face a crisis situation to provide abundant, reliable clean energy power to meet the nation's future productivity, economic growth and quality of life. The discovery of oxide high temperature superconductors (HTSs) made superconductor applications possible at liquid nitrogen temperature, but also presented a fascinating research topic due to their unusual physical properties, resulting in profound effects on Jc. Raising Jc in HTSs has been the focus of world-wide efforts in the field of applied superconductivity during the past two decades. In particular, a long-standing question is whether the theoretically predicted maximum Jc (so-called depairing limit) can be reached in practical HTS conductors through precise control of material microstructures with nanoscale precision. Recent advances in nanoscience have provided fresh opportunities in engineering the microstructures of HTS materials. The approach undertaken in this project of designing physical properties via controlling the electric current at the nanoscale represents a leap forward from the traditionally empirical method in which the HTS materials have been developed without a precise guidance of fundamental physics. Such a research also provides the forefront of education for the next generation in the fields of nanoscience and material science. TECHNICAL DESCRIPTION: Controlling microstructure with nanoscale precision is the key to achieving materials with extraordinary functionality and has been a major challenge in material research of HTS and other technologically interesting materials due to lack of understanding of fundamental physics and approaches for engineering atomic arrangement at such a scale. An integrated modeling-synthesis-characterization approach is being used to address such a challenge to understand, predict and manipulate the strained interfaces in functional nanocomposites of artificial pinning centers (APCs) embedded in HTS films of YBa2Cu3O7-d (YBCO). The goal is to achieve controllable self-assembly of APCs with precisely designed morphology, orientation, density and controlled APC/HTS interfaces to function optimally based on the basic physics design rules. Four integrated themes are proposed; all are focused on understanding and manipulating interface strains towards controllable growth of APC/YBCO nanocomposites for high Jc. Theme 1 focuses on the study of this configuration's phase diagram with a linear arrangement of APCs through understanding the microscopic controlling mechanisms at different dopant concentrations and YBCO matrix strains. The role of strain on the relevant interfaces will be quantified. Theme 2 investigates the effect of strained interfaces of linear APCs in a YBCO matrix on the Jc of the APC/HTS nanocomposites and explores ways to reduce or eliminate the detrimental effect of the oxygen disorder at such a strained interface on superconductivity of the nanocomposites films. Theme 3 focuses on a search for linear APCs with smaller diameters that approach the superconducting coherence length as well as higher density, correlated linear APCs for higher Jc at very high magnetic fields. Theme 4 investigates the kinetics of the spontaneous self-assembly of nanostructures.