Alloys and Compounds for Thermoelectric and Solar Cell Applications X: Session III and IV
Sponsored by: TMS Structural Materials Division, TMS Functional Materials Division, TMS: Alloy Phases Committee
Program Organizers: Hsin-Jay Wu, National Chiao Tung University; Sinn-wen Chen, National Tsing Hua University; Franck Gascoin, CNRS Crismat Unicaen; Philippe Jund, Montpellier University; Yoshisato Kimura, Tokyo Institute of Technology; Takao Mori, National Institute For Materials Science; Alexandra Zevalkink, Michigan State University; Wan-Ting Chiu, Tokyo Institute of Technology; Pai-chun Wei, National Taiwan University

Tuesday 8:00 AM
March 1, 2022
Room: 303D
Location: Anaheim Convention Center

Session Chair: Yoshisato Kimura, Tokyo Institute of Technology; Philippe Jund, Montpellier University


8:00 AM  Invited
Electronic and Phononic Features for High Thermoelectric Performance in Half-Heusler Materials: David Singh1; Zhenzhen Feng2; 1University of Missouri; 2Henan University
    The thermoelectric figure of merit, ZT, is a combination of thermal and electrical transport quantities that is strongly contraindicated in the sense that the particular combination of high electrical conductivity, high thermopower and low thermal conductivity does not naturally occur in textbook models. This talk discusses electronic and lattice dynamical features that resolve these contradictions in half-Heuslers thus providing ways of designing and discovering new themoelectrics. This includes a generalization of the concept of rattling to achive low thermal conductivities and the use of a fitness function that characterized the decoupling of conductivity and thermopower based on band structure features.

8:20 AM  
Ultra-high Solubility of Al and Enhanced Thermopower in Fe2VAl1+x: Michael Parzer1; Fabian Garmroudi1; Alexander Riss1; Takao Mori2; Ernst Bauer1; 1TU Wien; 2National Institute of Materials Science
    Recently, a record-breaking power factor of over 10 mW/mK2 was achieved in n-type Fe2VAl-based compounds, sparking new interest in full-Heusler systems for thermoelectrics. Here, we propose phase-boundary mapping in the Al-rich part of the phase diagram as a strategy to achieve high thermoelectric performance for p-type Fe2VAl-based compounds. Increasing the Al concentration up to Fe2VAl2, we find full solubility of Al using X-ray diffraction and scanning electron microscopy measurements. The transport properties - measured in a wide temperature range from 4-800 K - indicate non-rigid band structure behavior as the thermopower steadily increases up to Fe2VAl1.5, surpassing the original compound by over 100 %. Furthermore, the introduction of antisites into the crystal lattice leads to a significant reduction of the thermal conductivity. Therefore, this poses a powerful starting point for the discovery of new optimized thermoelectric materials, drastically extending the phase space of Fe-V-Al-based semiconducting compounds.

8:40 AM  
High-throughput Transport Property Measurements of Additively Manufactured Thermoelectric Materials: Dylan Kirsch1; Vijayabarathi Ponnambalam2; Joshua Martin1; Connor Headley3; Saniya LeBlanc2; Prasanna Balachandran3; Ji Ma3; 1National Institute of Standards and Technology; 2George Washington University; 3University of Virginia
    Widespread adoption of thermoelectric (TE) energy conversion technology has been hindered by low conversion efficiency and high device production costs. In contrast to traditional TE device manufacturing methods, powder-bed additive manufacturing (AM) is now being explored to print components with unique and controllable geometries, with the potential to reduce assembly steps, material waste, and production time and costs. A primary challenge of AM TE materials is the optimization of the processing parameters that affect the solidification microstructure and thereby the macroscale transport properties. To elucidate these processing-structure-property relationships, we synthesized material libraries that contain discrete processing parameters and subsequently performed high-throughput transport measurements on each region. We will present high-throughput electrical resistance and Seebeck coefficient measurements, along with bulk heat capacity and diffusivity measurements. We will emphasize key insights into processing-structure-property relationships that enable the tuning of AM parameters for producing higher efficiency and lower cost TE devices.

9:00 AM  Invited
The Role of Additive Manufacturing in Tailoring Thermoelectric Leg Shape and Transport Properties: Saniya Leblanc1; Bengisu Sisik1; Ryan Welch1; Yahya Oztan1; Vijayabarathi Ponnambalam1; 1George Washington University
    The advent of new manufacturing techniques such as additive manufacturing enables customizable thermoelectric device shapes, but there is little knowledge about what shapes are desirable and what impact additive manufacturing processes have on transport properties. In this work, we show the effect of different (non-rectangular) thermoelectric leg designs on thermoelectric device performance. Various leg shapes (rectangular prisms, rectangular prisms with interior hollows, trapezoids, hourglass, and Y-shapes) and two materials (bismuth telluride and silicon germanium) were modeled numerically to determine their thermal and electrical performance under constant temperature and heat flux boundary conditions for low and high temperature applications. Laser powder bed additive manufacturing experiments were conducted on both materials, and transport properties (Seebeck coefficient, electrical conductivity, thermal diffusivity) as well as microstructure were characterized. The results provide insight about how additive manufacturing may enable topological optimization of thermoelectric devices.