High-Entropy Alloy Superconductors under High Pressures

University Of Alabama At Birmingham, Birmingham AL

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY Superconductors play a vital role in various sectors of the US economy ranging from energy transmission, medical imaging, magnetically confined plasma for fusion energy generation, high-speed transportation, as well as quantum computing and information technology. Superconducting materials are special because they exhibit zero resistance to current flow and spontaneously expel magnetic fields below a critical transition temperature. High-entropy alloys are a special class of metal that has near equal amounts of typically five or more elements as opposed to more conventional alloys that usually add small amounts of several elements to one base (e.g. Iron, Nickel, Cobalt). High-entropy alloys represent a new addition to the family of superconductors as they show a phenomenon of robust superconductivity, where the superconducting transition temperature is unaffected even when the material is subjected to very high pressure. This work is uncovering a fundamental understanding of the superconducting phenomenon in high-entropy alloys for the purposes of tailoring their microstructure using 3-D printing techniques to further enhance their ability to generate higher magnetic fields required for practical applications. This project supports graduate and undergraduate students who are receiving training at national experimental and computational facilities, leading to a pipeline of well-rounded materials science graduates for employment in academia, national laboratories, and industry. The University of Alabama at Birmingham in partnership with the Historically Black Colleges and Universities in the southeastern region jointly undertake efforts in broadening participation of underrepresented groups in the science and engineering fields. PART 2: TECHNICAL SUMMARY In this project, combined theoretical and experimental expertise is called upon to investigate the phenomenon of robust superconductivity in high-entropy alloys at high-pressures and low-temperatures. Four-probe electrical resistance and magnetic susceptibility measurements on three classes of high-entropy alloy superconductors crystallizing in body-centered cubic phase (TiZrHfTaNb), hexagonal close-packed phase (TiZrHfReNb), and Cesium-Chloride type phase (RhPdScZrNb) are being conducted. The superconducting measurements are being extended to low temperatures of 1.9 K and pressures as high as 200 GPa using a custom diamond anvil with embedded probes for electrical transport and magnetic susceptibility measurements. The crystal structures of high-entropy alloy superconductors under high-pressures and low temperatures are also being examined using a synchrotron x-ray source. This study is providing corresponding first-principles calculations based on density functional theory, electron-phonon calculations, and stochastic random structures across three classes of high-entropy alloys as a function of external pressure. The resulting simulations of structural, electronic, and superconducting properties are being compared directly with experiments, which are helping benchmark the computational frameworks. Current studies on 3-D printed high-entropy alloy superconductors are offering unique microstructural control that increases the upper critical magnetic field which is of importance for practical applications of superconductors. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.