Alloys and Compounds for Thermoelectric and Solar Cell Applications VIII: Student Poster Session
Sponsored by: TMS Functional Materials Division, TMS: Alloy Phases Committee
Program Organizers: Sinn-wen Chen, National Tsing Hua University; Franck Gascoin, Ensicaen University of Caen; Philippe Jund, Montpellier University; Yoshisato Kimura, Tokyo Institute of Technology; Lan Li, Boise State University; Takao Mori, National Institute For Materials Science; Hsin-jay Wu, National Chiao-tung University; Tiejun Zhu, Zhejiang University

Monday 5:30 PM
February 24, 2020
Room: Sails Pavilion
Location: San Diego Convention Ctr

Session Chair: Sinn-wen Chen, National Tsing Hua University


D-4: Assessment of Co-P Diffusion Barrier for Bismuth Telluride-based Thermoelectric Materials: Zhen-Wei Sun1; Chun-Hsien Wang1; Albert T. Wu1; 1National Central University
    Bismuth telluride (Bi2Te3) is commonly used as thermoelectric materials owing to high figure of merit (zT) at low temperature range. The module requires the joining between Bi2Te3 and commercial Sn-based solder. The materials would react severely at the interface when assembling the module. Fast growing SnTe and Bi precipitates would deteriorate the thermoelectric performance and reliability of the module. To inhibit the formation of SnTe and Bi-rich phase, electroless cobalt-phosphorus (Co-P) layer is added to serve as an effective diffusion barrier on Bi2Te3-based substrate. The interfacial stability and the mechanical strength of the joints were improved. The results show that Co-P diffusion barrier can be used to enhance the reliability of the thermoelectric module.

Cancelled
D-5: Mass Production of Highly Performing BiSbTe Thermoelectric Materials Through Powder Metallurgy: Pathan Sharief1; Suk-Min Yoon1; May Likha Lwin1; Chul-Hee Lee1; Peyala Dharmaiah1; Babu Madavali1; Soon-Jik Hong1; 1Kongju National University
    Thermoelectrics (TE), a competent energy conversion technology capable of converting abundant waste heat into electricity and vice versa, which improves fuel efficiency of automobiles and reduces greenhouse gas emissions from conventional refrigerators. To implement efficient thermoelectrics into active commercial products, the device requires high figure of merit (ZT) and consequently mass-production of powders with uniform microstructure is highly demanding. Many researchers had achieving high ZT but unable to fabricate high amount of powder which is not suitable for thermoelectric industries. In here, we report that powder metallurgy had capacity of producing BiSbTe thermoelectric materials with high figure of merit and mass production rate of about 2-3 kg/min feasible for many thermoelectric applications. The produced powders, consolidated bulk samples were systematically analyzed by XRD, XRF, SEM-EDS, and TEM respectively. The sample’s electrical and thermal properties were measured by Seebeck measurement system, laser flash method and achieved high figure of merit.

D-6: Phase Diagram of Bi-Cu-Te and Thermoelectric Properties of Cu Doped Bi2Te3 Alloys: Wan-Ting Yen1; Hsin-Jay Wu1; 1National Chiao Tung University
    Thermoelectric material (TE) could convert waste heat directly into electricity, and therefore it could pave the way toward the environmental sustainability. The layered-structure Bi2Te3, which crystallize in a rhombohedral symmetry, show anisotropic transport properties, and are the most well-established room-temperature TE materials. Herein we aim to tune the thermal/electrical transport properties of the Bi2Te3-based alloys, by incorporating minor amount of Cu, to form a series of Cu-doped Bi2Te3 alloys. The homogeneity regime, phase stability and microstructural evolution are elaborated by establishing the 523K isothermal section of ternary Bi-Te-Cu, using the thermally-equilibrated or solidified alloys. In addition, the TE properties of selective Cu-doped Bi2Te3 alloys that grown by the Bridgman method suggest that the small deviations in the starting compositions could lead to the huge the difference in the resultant TE performance.

D-7: Phase Diagrams of Ag-Pb-Sn-Te System: Sinn-wen Chen1; Jia-yu Du1; Yohanes Hutabalian1; Aleš Kroupa2; 1National Tsing Hua University; 2Czech Academy of Sciences
    Ag-Pb-Sn-Te is an important material system for thermoelectric applications. Various compounds in this system, such as Ag2Te, PbTe, SnTe, (Pb,Sn)Te, are promising thermoelectric materials. There are no phase equilibria information of the Ag-Pb-Sn-Te quaternary system, and limited phase equilibria literatures of the four ternary subsystems, Ag-Pb-Sn, Ag-Pb-Te, Ag-Sn-Te and Pb-Sn-Te. Phase diagrams of Ag-Pb-Te and Pb-Sn-Te are adopted from literatures. Experimental measurements are carried out to determine phase equilibria of Ag-Pb-Sn, Ag-Sn-Te and Ag-Pb-Sn-Te at 350℃. One ternary compound, AgSnTe2, is observed. No other ternary compounds and quaternary compounds are found. PbTe and SnTe form a continuous solid solution (Pb,Sn)Te in the Pb-Sn-Te system. There are two tie-triangles, Ag+ζ-Ag4Sn+Liquid and ζ-Ag4Sn+Liquid+ε-Ag3Sn, in the Ag-Pb-Sn isothermal sections at 350℃. There are eight tri-angles in the Ag-Sn-Te system. The isothermal tetrahedron of the Ag-Pb-Sn-Te quaternary system at 350℃ is proposed based on the literature results and those determined in this study.

D-8: Realizing the Microstructure in GeTe-based Thermoelectric Materials and Phase Transition Behavior: Yi-Fen Tsai1; Pai-Chun Wei2; Hsin-Jay Wu1; 1National Chiao-Tung University; 2Computer, Electrical, and Mathematical Sciences and Engineering Division King Abdullah University of Science and Technology (KAUST)
    Lately, the thermoelectric community has been fascinated by the Germanium-tellurides (GeTe-based alloys) which feature high electrical conductivity and high thermal conductivity. Additionally, the GeTe undergoes a phase transition from the low-temperature rhombohedral α-GeTe to high-temperature cubic β-GeTe at 673 K, which induces the discontinuities in temperature-dependent TE property curves. In this work, the GeTe is doped with multiple dopants (e.g., Sb, Cu, Se, Bi, Ga, Mn, Sn.) via long-term heat treatment, and we further realized that the α-to-β phase transition could be greatly affected by the dopants. For example, the addition of Sb, Se, and Mn effectively lower the α-to-β phase transition temperature, and can be viewed as stabilizers for cubic β-GeTe. The compositional homogeneity and microstructural texture for α-GeTe and β-GeTe varies dramatically in those Sb-, Se- and Mn-doped GeTe, which eventually leading to a wide distribution in their zT peak values, ranging from 0.8 to above 2.

D-9: Thermoelectric Properties of Multiply Doped Mg3(Sb, Bi)2: Yasuo Shibata1; Yuji Ohishi1; Hiroaki Muta1; 1Osaka University
     Tamaki et al. reported that Te-doped Mg3(Sb, Bi)2 exhibited a very high ZT of 1.5 around 700 K with a largely enhanced electrical transport performance due to the significant valley degeneracy at the conduction band. According to Li’s first-principles calculation, when the carrier concentration reaches 4.8×1020 cm-3, the maximum ZT value of Mg3Sb2 can be enhanced by 88% compared with the reported value. However, this high carrier concentration has not been achieved in previous research. In the present study, we synthesized both cation and anion-site doped Mg3(Sb, Bi)2 in order to reach high carrier concentration.