Abstract
Thermoelectric materials, capable of converting temperature gradients into electrical power, have been traditionally limited by a trade-off between thermopower and electrical conductivity. This study introduces a novel, broadly applicable approach that enhances both the spin-driven thermopower and the thermoelectric figure-of-merit (zT) without compromising electrical conductivity, using temperature-driven spin crossover. Our approach, supported by both theoretical and experimental evidence, is demonstrated through a case study of chromium doped-manganese telluride, but is not confined to this material and can be extended to other magnetic materials. By introducing dopants to create a high crystal field and exploiting the entropy changes associated with temperature-driven spin crossover, we achieved a significant increase in thermopower, by approximately 136 μV K−1, representing more than a 200% enhancement at elevated temperatures within the paramagnetic domain. Our exploration of the bipolar semiconducting nature of these materials reveals that suppressing bipolar magnon/paramagnon-drag thermopower is key to understanding and utilizing spin crossover-driven thermopower. These findings, validated by inelastic neutron scattering, X-ray photoemission spectroscopy, thermal transport, and energy conversion measurements, shed light on crucial material design parameters. We provide a comprehensive framework that analyzes the interplay between spin entropy, hopping transport, and magnon/paramagnon lifetimes, paving the way for the development of high-performance spin-driven thermoelectric materials.
Original language | English |
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Journal | Energy and Environmental Materials |
DOIs | |
State | Accepted/In press - 2024 |
Funding
The authors like to acknowledge the funding support by the National Science Foundation (NSF) under grant numbers CBET\u20102110603 and the Air Force Office of Scientific Research (AFOSR) under contract number FA9550\u201012\u20101\u20100225. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This work was partly performed at the Analytical Instrumentation Facility (AIF) at North Carolina State University, supported by the State of North Carolina and the National Science Foundation (award number ECCS\u20102025064).
Funders | Funder number |
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National Science Foundation | CBET‐2110603 |
Air Force Office of Scientific Research | FA9550‐12‐1‐0225 |
North Carolina State University | ECCS‐2025064 |
Keywords
- magnons
- paramagnons
- spin crossover
- thermoelectric materials
- thermopower enhancement