High-Entropy Alloy Superconductors under High Pressures

第1部分：非技术性超导体在美国经济的各个领域发挥着至关重要的作用，从能源传输、医学成像、用于聚变发电的磁约束等离子体、高速运输以及量子计算和信息技术。超导材料是特殊的，因为它们对电流流动表现出零阻力，并在临界转变温度以下自发地排出磁场。高熵合金是一种特殊的金属类别，通常含有几乎相等的五种或五种以上元素，而更传统的合金通常在一个基础上添加少量的几种元素(例如铁、镍、钴)。高熵合金代表着超导体家族的新成员，因为它们显示出一种强大的超导现象，即使在材料处于非常高的压力下，超导转变温度也不受影响。这项工作揭示了对高熵合金中超导现象的基本理解，目的是利用3D打印技术来定制其微观结构，以进一步增强其产生实际应用所需的更高磁场的能力。该项目支持在国家实验和计算设施接受培训的研究生和本科生，从而培养出一批全面发展的材料科学毕业生，在学术界、国家实验室和工业中就业。阿拉巴马大学伯明翰分校与东南地区历史上的黑人学院和大学合作，共同努力扩大未被充分代表的群体在科学和工程领域的参与。第2部分：技术总结在这个项目中，结合理论和实验专业知识来研究高熵合金在高压和低温下的强超导性现象。用四探针法测量了体心立方相(TiZrHfTaNb)、六方密堆积相(TiZrHfReNb)和氯化铯类相(RhPdScZrNb)三种高熵合金超导体的电阻和磁化率。超导测量将扩展到1.9K的低温和高达200 Gpa的压力，使用带有嵌入探头的定制金刚石顶锤进行电气传输和磁化率测量。高熵合金超导体在高压和低温下的晶体结构也正在使用同步加速器x射线源进行研究。本研究提供了基于密度泛函理论、电子-声子计算和三类高熵合金的随机随机结构随外压变化的相应的第一性原理计算。由此产生的结构、电子和超导性质的模拟正在直接与实验进行比较，这些实验有助于对计算框架进行基准测试。目前对3D打印高熵合金超导体的研究提供了独特的微结构控制，增加了上临界磁场，这对超导体的实际应用非常重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARYSuperconductors 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 SUMMARYIn 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.