A giant Nernst power factor and figure-of-merit in polycrystalline NbSb2 for Ettingshausen refrigeration

Ettingshausen refrigeration is a promising solid-state refrigeration technology that can be used in exploring the quantum state of matters and superconducting materials, but its development is greatly limited by the lack of high-performance polycrystalline thermomagnetic materials. In this work, we report that the polycrystalline topological semimetal NbSb2 has a giant Nernst power factor ((PF)(N)) of 1269 x 10(-4) W m(-1) K-2 under 9 T at 28 K and a Nernst figure-of-merit (z(N)) of 28.5 x 10(-4) K-1 under 9 T at 18 K, both of which are record-high values among the polycrystalline thermomagnetic materials. The observed high thermomagnetic performance is mainly attributed to the large and unsaturated Nernst thermopower under a high magnetic field. Due to the diminished anisotropy, the polycrystalline NbSb2 has similar high carrier mobility to the single-crystalline NbSb2 in the bc-plane, yielding large Nernst thermopower in low temperature ranges. Combining the excellent thermomagnetic performance and low-cost and time-saving fabrication process, polycrystalline NbSb2 is a very competitive candidate material for Ettingshausen refrigeration.

Automated summary

Ettingshausen refrigeration, a solid-state refrigeration technology, lacks high-performance polycrystalline thermomagnetic materials. In this study, we report the giant Nernst power factor (PF(N)) and Nernst figure-of-merit (z(N)) of polycrystalline topological semimetal NbSb2, which are record-high values among polycrystalline thermomagnetic materials. The high thermomagnetic performance of NbSb2 is attributed to its large and unsaturated Nernst thermopower under a high magnetic field. Polycrystalline NbSb2, with its excellent thermomagnetic performance and low-cost fabrication process, is a competitive candidate material for Ettingshausen refrigeration.