Researchers at Tokyo Metropolitan University used large amounts of data on simple superconducting materials with specific crystal structures to mix and design a new type of high-entropy alloy (HEA) superconductor. It is known that HEA can maintain superconducting properties under extremely high pressures. New superconductor, Co0.2you0.1use0.1rhodium0.3iridium0.3zirconium2, Has a superconducting transition at 8K, which is a relatively high temperature for HEA. The team’s method may be suitable for discovering new superconducting materials with specific ideal properties.
It has been more than one hundred years since the discovery of superconductivity. In superconductivity, certain materials are found to suddenly exhibit the smallest resistance to currents below the transition temperature. When we explore ways to eliminate power waste, a way to significantly reduce power transmission losses is a fascinating prospect. However, the widespread use of superconductors is hindered by the requirements of existing superconductors, especially low temperature requirements. Scientists need a way to discover new superconducting materials without trial and error and adjustment of key properties.
A team led by Associate Professor Yoshiichi Mizuguchi of Tokyo Metropolitan University is developing a “discovery platform” that has led to the design of many new superconducting materials. Their method is based on high-entropy alloys (HEA), in which certain sites in a simple crystal structure can be occupied by five or more elements. After being applied to heat-resistant materials and medical equipment, some HEAs have been found to have superconducting properties and have some special characteristics, especially maintaining zero resistivity under extreme pressure. The team investigated materials databases and cutting-edge research, and discovered a series of superconducting materials with the same crystal structure but different elements at specific locations. Then, they mixed and designed structures that contained many elements. Throughout the crystal, those “HEA positions” are occupied by one of the mixed elements (see Figure 1). They have successfully created a layered bismuth sulfide superconductor with a sodium chloride crystal structure and a high-entropy variant of telluride.
In their latest work, they focused on copper aluminide (CuAl2) Structure.Combining transition metal element (Tr) and zirconium (Zr) into TrZr compound2 Superconducting materials with this structure are known, in which Tr can be Sc, Fe, Co, Ni, Cu, Ga, Rh, Pd, Ta, or Ir. The team used arc melting technology to combine a “cocktail” of these elements to create a new HEA-type compound Co0.2you0.1use0.1rhodium0.3iridium0.3zirconium2, Showing superconducting properties. They studied the resistivity and specific heat of electrons, as well as the energy used by electrons in the material to increase temperature, and determined a transition temperature of 8.0K. For HEA-type superconductors, this is not only relatively high, but they confirmed that the material has a sign of “overall” superconductivity.
The most exciting aspect is that a variety of other transition metals and ratios can be tried and adjusted to achieve higher transition temperatures and other required properties without changing the underlying crystal structure. The team hopes that their success will lead to the discovery of more new HEA-type superconductors in the near future.
Use high-entropy alloys to make new layered superconductors
Yoshikazu Mizuguchi et al. Superconductivity in CuAl2Type company0.2you0.1use0.1rhodium0.3iridium0.3zirconium2 Transition metal sites with high entropy Material Research Letter (2020). DOI: 10.1080 / 21663831.2020.1860147
Provided by Tokyo Metropolitan University
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