PhD Thesis Proposal: Russell Taylor

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Meeting ID: 981 7864 8526
Passcode: 319148

"Disorder engineering and carrier density tuning for high performance p-type Fe₂VAl thermoelectric materials"

Abstract

Even while global electrification increases, the demand for fossil fuels is expected to remain high, and with over 60% of this energy lost as waste heat, there is an immense opportunity to improve system efficiency through energy harvesting with thermoelectric materials. 

Fe₂VAl is a promising, strongly-ordered, intermetallic compound that is an eco-friendly, low-cost, and easy-to-process potential replacement for conventional, low-temperature, thermoelectric materials like Bi₂Te₃ and Sb₂Te₃, which are brittle and use toxic, expensive elements. The disordered and metastable phases of Fe₂VAl, of which we have developed a method to quantify, can enhance both thermal and electrical properties. Initial trials indicate the composition can be optimized for favorable thermal properties through electro-pulse annealing, a Joule-heating and rapid quenching process.

A key factor in achieving desirable electrical properties is the carrier density, which can be challenging to measure in high-carrier density materials like Fe₂VAl. Using a method we developed, we propose that we can tune carrier density to an optimal value where peak electrical performance is achieved, without sacrificing the thermal properties. Through a novel compensation doping strategy, we aim to introduce n-type doping into p-type materials to reach desired carrier densities. Our n-type alloy, Fe₂VAl_0.9Ge_0.1, has achieved a record ZT of 1.2, with a high Seebeck coefficient enhanced by ferromagnetic phase stabilization. However, our best-performing and record p-type alloy, Fe₂V_0.7Al_1.3, has only reached a ZT of ~0.25. By combining off-stoichiometric Al-rich compositions with Ge, we aim to leverage the best properties of each to achieve new record p-type efficiencies in compensation-doped Fe₂V_1-x-yAl_1+xGe_y.

Proposed work: 1) efficiency improvement through carrier density tuning in Fe₂V_1-x-yAl_1+xGe_y compensation-doped alloys, 2) optimization of thermal treatments to improve ZT through electro-pulse annealing, and 3) validation of performance with a thermoelectric generator.

Thesis Committee

• Ian Baker (Chair)
• Jifeng Liu (co-advisor, project lead)
• Yan Li
• Geoffroy Hautier (external)

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu.