Alloys and Compounds for Thermoelectric and Solar Cell Applications IX: Session I
Sponsored by: TMS Functional Materials Division, TMS Structural 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; Lan Li, Boise State University; Takao Mori, National Institute For Materials Science; Tiejun Zhu, Zhejiang University; Alexandra Zevalkink, Michigan State University; Wan-Ting Chiu, Tokyo Institute of Technology
Monday 8:30 AM
March 15, 2021
Room: RM 21
Location: TMS2021 Virtual
Session Chair: Hsin-Jay Wu, National Chiao-Tung University; Albert T. Wu, National Central University
8:30 AM
Introductory Comments: Alloys and Compounds for Thermoelectric and Solar Cell Applications IX: Hsin-Jay Wu1; 1National Chiao Tung University
Introductory Comments
8:35 AM Invited
n-Bi2-xSbxTe3 as an Alternative to Mainstream n-Bi2Te3-xSex Near Room Temperature: Jian He1; Lipeng Hu2; 1Clemson University; 2Shenzhen University
For decades n-type Bi2Te3-xSex compounds have remained the mainstream n-type thermoelectric material for solid-state cooling and power generation near room temperature. However, the performance of n-type Bi2Te3-xSex is inferior to that of p-type Bi2-xSbxTe3 near room temperature, restricting the device efficiency. In this work, we developed high performance n-type Bi2-xSbxTe3, a composition long thought to only make good p-type thermoelectrics, owing to a synergy of the following: (i) The donor-like effect is compensated by the antisite defects regulated by Sb alloying; (ii) the conduction band degeneracy increases from 2 for Bi2Te3 and Bi2Te3-xSex to 6 for Bi2-xSbxTe3, favoring high Seebeck coefficients; and (iii) larger mass fluctuation but smaller electronegativity difference and smaller atomic radius difference between Bi and Sb than those between Se and Te effectively suppress the lattice thermal conductivity and retains decent carrier mobility. A state-of-the-art zT of 1.0 near room temperature was attained in hot deformed Bi1.5Sb0.5Te3.
8:55 AM Invited
Enhanced Thermoelectric Figure-of-Merit in Nanostructured n-type Bi2Te3 via Phase Diagram Engineering: Hsin-Ching Huang1; Wan-Ting Yen2; Hsin-Jay Wu2; 1National Sun Yat-sen University; 2National Chiao Tung University
Bismuth tellurides have been one of the most well-established thermoelectric (TE) coolers since the 1960s. Nevertheless, the research interest for this layered-structure material has not been faded away, given that there are still breakthroughs in its conversion efficiency being reported. Herein, an emerging thermodynamic approach by using an equilibrium phase diagram is being adopted to probe the high-zT zone for the n-type Ag-Bi2Te3. In particular, the best-performing Ag-Bi2Te3 reveals an Ag-rich inclusion along the grain boundaries, which further embedding with the dense nano-precipitation inside the grain. Nanostructured Ag-Bi2Te3 bulks, therefore, result in extraordinary power factor and reduced lattice thermal conductivity.
9:15 AM Invited
Unique Influences of Laser Additive Manufacturing on Multiscale Structuring of Bismuth Telluride Thermoelectric Materials: Saniya Leblanc1; Ryan Welch1; Bengisu Sisik1; 1George Washington University
Additive manufacturing can overcome challenges posed by traditional thermoelectric device. This talk will describe our progress in laser-based additive manufacturing of bismuth telluride using a laser additive process that locally melts successive layers of material powder to construct 3D objects. This technique could enable new device architectures and multiscale structuring. We will discuss the impact of laser-induced, rapid melting and solidification on nano-, micro- and meso-structure. We explain the relationship between laser processing parameters and the melt pool geometry, grain structure, and porosity. Transmission electron microscopy investigations of the nanostructure show disperse oxide inclusions that explain transport property measurement results. Investigation of processed material’s nanostructure also shows the unique grain boundaries and dislocations that result from laser processing. Finally, we show numerical modeling of different thermoelectric leg geometries enabled by additive manufacturing.
9:35 AM Invited
Assessment of Electroless Cobalt Diffusion Layer for Bi2Te3-based Thermoelectric Module: Albert T. Wu1; Chun-Hsien Wang1; 1National Central University
This study investigates the effect of using an electroless Co-P layer as the diffusion barrier when assembling thermoelectric module. The effect of adding the diffusion barrier on the interfacial reaction, mechanical behavior and thermoelectric properties of thermoelectric joints is discussed. When directly bonded solders with thermoelectric substrates, various intermetallic compounds (IMCs) form at the interface will affect the stability of the thermoelectric joints. The addition of a Co-P diffusion barrier will significantly improve the interfacial stability and effectively inhibit the formation of brittle IMC. The joint shear strength is greatly improved and the fracture mode becomes more ductile due to the added barrier layer. The addition of the Co-P diffusion barrier does not cause a significant deterioration in thermoelectric properties. These findings indicate that the Co-P layer is a promising diffusion barrier for Bi2Te3-based thermoelectric module.
9:55 AM
Effect of Interfacial Reaction on Bi2Te3 and Sb2Te3 Thin-film Thermoelectric Module: Kai-Wen Cheng1; Zhen-Wei Sun1; Albert T. Wu1; 1National Central University
The interfacial reaction between thermoelectric materials and metal electrode becomes crucial when decreasing the dimension of thin-film module. Serious atomic interdiffusion at the interface may affect the electrical and thermoelectric properties of the module. In this study, Bi2Te3 and Sb2Te3 are selected respectively as the n- and p-type thermoelectric materials in the module for their small band gap and excellent zT values at room temperature range. Cu and Ni are chosen as the electrodes for their high electrical conductivity. To simulate the operating condition, the modules are aged for different duration of times at elevated temperatures. Atomic diffusion in the thermoelectric thin-film from the electrodes and its crystallographic relationship is investigated. Thermoelectric properties are measured to understand the effect of the interfacial stability for the thin-film modules.
10:15 AM
Thermomagnetic Properties of Single-crystal 2H-NbSe2 and Bi2Te3: Md Sabbir Akhanda1; S. Emad Rezaei1; Md Golam Rosul1; Keivan Esfarjani1; Sergiy Krylyuk2; Albert Davydov2; Mona Zebarjadi1; 1University of Virginia; 2National Institute of Standards and Technology
Magneto-thermoelectric properties of topological materials recently have caught much attention for their potential in the heat-to-electricity energy conversion process. In this work, the Nernst coefficient, magneto-Seebeck, and magnetoresistance of two topological single-crystal materials: 2H-NbSe2 and Bi2Te3, were investigated over a wide temperature range. Seebeck coefficient, electrical conductivity, and thermal conductivity measurements are also presented to provide insight into the transport properties. Nernst coefficient measurements have been compared with the Moreau’s relation to validating the overall trend. Theoretical predictions based on first-principles calculations were included to substantiate the experiments. In the case of Bi2Te3, we observe that the Nernst coefficient and the magneto-Seebeck both increase as the temperature decreases which can be attributed to the increase of the carrier mobility. Despite the fact that NbSe2 is a Weyl semimetal with bipolar conduction, we observe a very small Nernst coefficient at room temperature that further decreases as the temperature decreases.