Alloys and Compounds for Thermoelectric and Solar Cell Applications XI: Poster Session
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; Takao Mori, National Institute For Materials Science; Wan-Ting Chiu, Tokyo Institute of Technology; Chenguang Fu, Zhejiang University
Monday 5:30 PM
March 20, 2023
Room: Exhibit Hall G
Location: SDCC
C-1: Compositional Modification Improves the Thermoelectric Performance of AgSbTe2: Bo-Chia Chen1; Hsin-Jay Wu1; 1National Yang-Ming Chiao Tung University
In the mid-temperature range, AgSbTe2 is a potential thermoelectric compound. Their thermal and electrical properties can be efficiently optimized by even slightly altering the ratio of each element. The figure-of-merit zT is only one at 623 K due to the power factor (S2ρ) negatively impacting the high electrical resistivity (ρ). The stoichiometric ratios for the pure AgSbTe2 are tweaked in this study, resulting in a more significant Seebeck coefficient (S) and better electrical conductivity. The figure-of-merit zT rose to 1.4 with the low thermal conductivity (κ) combined. Second, following correct doping, the κ and κL are further lowered, but the power factor remains intact. Our AgSbTe2-based alloys surpass most AgSbTe2-based materials, with a peak zT of 1.7 at 623 K and an average zTave of 1.15 between 300 and 623 K.
C-2: Eliciting Promising p-type Bi2Te3 with Sizeable Thermoelectric Performances: Hung-Wei Chen1; Hsin-Jay Wu1; 1National Yang Ming Chiao Tung University
Due to the urgent demands for small device cooling and heat recovery applications, Thermoelectric (TE) materials have drawn significant interest in recent decades. Among various TE materials, Bismuth telluride (Bi2Te3) based alloys are the most potential candidate for near room-temperature applications, which have also been commercialized recently. In this study, we seek to enhance the TE performance of p-type Bi2Te3 materials by (i) modulating doping concentration in single-phase Bi2Te3 and (ii) inducing the liquid-like dopants into highly doped Bi2Te3. Our result demonstrates that a remarkable zT value can be presented in lightly-doped Bi2Te3 while a notable average zT (zTavg) can be observed in heavily-doped Bi2Te3. Hence, the zT value is improved by 30% (zT~ 1.6) compared to the previous p-type Bi2Te3, and an enhanced average zT (zTavg~ 1.2) is reported in the temperature range of 323 K to 493 K, representing the immense potential for future TE devices.
C-3: Interfacial Reactions in Cu/Se, Cu2Se/Te and Cu2Te/Se Couples: Yohanes Hutabalian1; Sinn-wen Chen1; 1National Tsing Hua University
Cu2Se-based and Cu2Te-based alloys are important thermoelectric materials. Interfacial reactions in the Cu/Se, Cu2Se/Te and Cu2Te/Se couples are determined in this study. Reaction products of CuSe2, Cu3Se2, CuSe and Cu2Se are observed in the Cu/Se reacted couple at 300oC. The Cu2Se/Te couple is prepared by heating Cu2Se substrate and Te shots together at 500oC for a very short time. Te melts and surrounds the Cu2Se substrate, and the Cu2Se/Te couple is quenched immediately. A very thick reaction zone is found in the as-quenched sample. A ternary compound, Cu3SeTe, is observed. The reaction path is Cu2Se/Cu3SeTe/CuTe/liquid at 500℃. A complicated reaction phases are observed found in the Cu2Te/Se couple reacted at 300oC. For only 10 min, a very thick layer of 147 mm thickness with various phases are found in the couple Cu2Te/Se. It is presumed that the Cu is the fastest diffusion species in both couples.
C-4: Liquid-like Copper Ionic and Multiscale Crystal Imperfections Eliciting Record-High Thermoelectric zT in n-type Bi2Te3: Wan-Ting Yen1; Hsin-jay Wu1; Kuang-Kuo Wang2; 1National Yang Ming Chiao Tung University; 2National Sun Yat-sen University
In the past ten years, Bismuth telluride-based thermoelectric (TE) materials have been proved to be widely used in waste heat recovery and electronic coolers. However, the peak zT of n-type counterparts have lower than p-type counterparts, and the peak zT is obtained at higher temperatures. This performance imbalance severely hinders its TE applications. In this work, the TE performance of n-type Bi2Te3 is improved by doping liquid-like copper chalcogenides Cu2X (X = S, Se, Te). Dilute Cu2X dopants are incorporated into Bi2Te3 crystals, aiming to boost carrier mobility by generating the highly-mobile Cu ions. Meanwhile, the dopants introduce nano-precipitates and multiscale crystal imperfections, leading to the κL for our best-performing sample reaching the amorphous limit of Bi2Te3. Hybrid crystalline materials with liquid-like superionic conductors could serve as a new route for alloy design, which decouples the interconnect transfer characteristics for breakthrough TE performance.
C-5: Low Crystallinity Cu-Te-S Compounds Elicit Ultralow Lattice Thermal Conductivity in GeTe Thermoelectric Materials: Yi-Fen Tsai1; Hsin-Jay Wu1; 1National Yang Ming Chiao Tung University
The promising thermoelectric material, germanium-telluride (GeTe), is one of the attractive based materials due to its outstanding electrical performance. The over-high thermal conductivity limited the TE performance in pristine GeTe. This work induced the liquid-like Cu2S with an ultralow thermal conductivity in the GeTe matrix. Compared to the high-cost material GeTe, cost-effective Cu2S has the characteristics of eco-friendly and is abundant on earth. The low crystallinity CuTeS compounds form in Cu2S-alloying GeTe as secondary phases, causing severe phonon scattering. The ultralow lattice thermal conductivity beats the amorphous limit from the Debye-Cahill model and boots the zT to 1.4 at 700 K.
C-6: Minor Cu Addition in β-Zn4Sb3 Leads to High Thermoelectric Performance via Phase Diagram Engineering: I-Lun Jen1; You-Kai Su2; Hsin-Jay Wu1; 1National Yang Ming Chiao Tung University; 2National Sun Yat-Sen University
Thermoelectric (TE) materials have attracted growing attention in recent decades. The p-type β-Zn4Sb3 has been an ideal candidate for mid-temperature TE generator, as it composes of cost-effective and environmental-friend elements. Even though β-Zn4Sb3 is known as a phonon-glass electron-crystal (PGEC) feature, the binary compound alloys face a barrier of thermal instability arising from the highly mobile zinc cations. Additionally, Phase Diagram Engineering is a useful method for determining the solubility range of Cu. In this work, a Zn-Sb-Cu system with a 623 K isothermal section is built. The greatest solubility in Zn4Sb3 at 623 K is less than 4% Cu. As a result, the Cu-addition (Zn4Sb3)1-yCuy alloys are created, and the improved power factor S2ρ-1 ~1.15 (mW/mk2) allows the alloy to reach a figure of merit zT of 0.97 at 623 K.