Alloys and Compounds for Thermoelectric and Solar Cell Applications X: Session I and II
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
Monday 8:30 AM
February 28, 2022
Room: 303D
Location: Anaheim Convention Center
Session Chair: Takao Mori, National Institute for Materials Science (NIMS); Hsin-Jay Wu, National Yang Ming Chiao Tung University
8:30 AM Introductory Comments
8:35 AM Invited
Advancing the Thermoelectric Performance
of Full Heusler Alloys: Ernst Bauer1; Fabian Garmroudi1; Matthias Knopf1; Alexander Riss1; Michael Parzer1; Takao Mori2; 1Technische Universität Wien; 2NIMS Tsukuba
XYZ (half-Heusler) and X2YZ (full-Heusler) ternaries form extended families of materials, with a large variety of ground states, hence, with numerous prospects for technical applications. Here, X and Y are transition metal elements and Z is a main group element. Both of these families crystallise in a cubic structure with the prototypic LiAlSi-structure (C1b-type) for the former and the Cu2MnAl-strucutre (L21-type) for the latter. The present work aims to demonstrate how appropriate co-substitutions in the full-Heusler system Fe2VAl dramatically enhances the thermoelectric performance, arriving at thermoelectric power factors (PF > 10 mW/m·K2 [1]), exceeding best performing Bi2Te3-based systems by a factor of 2 to 3 around room temperature. Here, experimental data will be analysed by DFT results, and by appropriate phenomenological models in order to trace the evolution of physical features. [1] F. Garmroudi et al., PRB, 103, 085202 (2021)Research supported by JST, project MIRAI.
8:55 AM
Rational Band Engineering Leads to Enhanced Thermoelectric Performance of Fe2VAl-type Heusler Compounds: Alexander Riss1; Fabian Garmroudi1; Michael Parzer1; Sergii Khmelevskyi1; Raimund Podloucky2; Kazuki Tobita3; Yukari Katsura4; Kaoru Kimura3; Takao Mori5; Ernst Bauer1; 1TU Wien; 2Universität Wien; 3The University of Tokyo; 4The University of Tokyo, Kashiwa; 5NIMS
The full-Heusler compound Fe2VAl exhibits a small pseudogap, setting a favourable playground for optimizations to achieve a high thermoelectric (TE) performance. Here, we present various electronic measurements of a set of n-type and p-type samples with the composition Fe2V1-xTaxAl1-ySiy in the range of 4 K to 800 K. The results are analyzed semiquantitatively using a parabolic band model and compared with those from density functional theory calculations. The band gap Eg is increased from almost zero toward Eg ~ 0.1 eV with increasing Ta substitution, consistent with the results from ab initio calculations. Due to the enhancement of the Seebeck coefficient, the power factor is boosted up to 10.3 mW/mK2. In addition, the thermal conductivity is further reduced when synthesized as a thin film.
9:15 AM
Anderson Transition as a Novel Route for High-performance Thermoelectrics: Fabian Garmroudi1; Michael Parzer1; Alexander Riss1; Andrei Ruban2; Sergii Khmelevskyi1; Michele Reticcioli3; Matthias Knopf1; Herwig Michor1; Andrej Pustogow1; Takao Mori4; Ernst Bauer1; 1Technische Universität Wien; 2KTH Royal Institute of Technology; 3Universität Wien; 4National Institute for Materials Science
Twenty-five years ago, Mahan and Sofo derived a mathematical idea for 'the best thermoelectric' − a delta-distribution-shaped transport function, where electrons contributing to transport exist only in an infinitely narrow energy interval. While the authors themselves thought that only approximations to this concept exist in nature, we recognize that this scenario is actually realized at the Anderson transition in an impurity band, i. e. the transition from Anderson-localized to extended quantum states. We present here, for the first time, a significant enhancement of the thermoelectric properties across such a transition in the full-Heusler compound Fe2VAl. This is achieved by controlling the level of atomic disorder and number of antisite defects by high-temperature quenching. Experimental results of the magnetic and transport properties confirm the picture drawn by our ab initio Monte-Carlo simulations and electronic structure calculations, suggesting a new route towards achieving high thermoelectric performance in all kinds of materials.
9:35 AM
NOW ON-DEMAND ONLY - Improvement of Thermoelectric Figure of Merit of p-type BiSbTe Alloys through the Microstructure Controlling by Optimization of Initial Powder Size: Babu Madavali1; Pathan Sharief1; Sungjae Jo1; Gian Song1; Soon-Jik Hong1; 1Kongju National University
In this work, we have fabricated p-type Bi0.5Sb1.5Te3 alloys and, eminently improved the thermoelectric properties through the controlling microstructure via optimization of initial powder size using water atomization. For that, we have partitioned different powder sizes such as 32-75μm, 75-125μm, 125-200μm and <200μm for the present study, and consolidated using sintering. The grain sizes were increased with increasing powder size, which further severely affect the transport properties. The electrical conductivity was high for 125-200μm sample owing to their large grain size and it decreased with decreasing powder size samples corresponding to their decreasing grain size. As a sequence, the Seebeck coefficient was decreased with increasing particle size. Besides, thermal conductivity also increased with increasing particle size due to higher transportation of carriers and phonons. The maximum figure of merit, ZT of 1.257, 1.24 was obtained for the 75-125μm, and 125-200μm samples respectively due to their higher electric conductivity.