Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology

Beijing, China

Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology

Beijing, China
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Kong X.,Beihang University | Zhu W.,Beihang University | Cao L.,Beihang University | Peng Y.,Beihang University | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2017

The contact resistance between metals and semiconductors has become critical for the design of thin-film thermoelectric devices with their continuous miniaturization. Herein, we report a novel interface tuning method to regulate the contact resistance at the Bi2Te3-Cu interface, and three Bi2Te3 films with different oriented microstructures are obtained. The lowest contact resistivity (∼10-7 cm2) is observed between highly (00l) oriented Bi2Te3 and Cu film, nearly an order of magnitude lower than other orientations. This significant decrease of contact resistivity is attributed to the denser film connections, lower lattice misfit, larger effective conducting contact area, and smaller width of the surface depletion region. Meanwhile, our results show that the reduction of contact resistance has little dependence on the interfacial diffusion based on the little change in contact resistivity after the introduction of an effective Ti barrier layer. Our work provides a new idea for the mitigation of contact resistivity in thin-film thermoelectric devices and also gives certain guidance for the size design of the next-level miniaturized devices. © 2017 American Chemical Society.


Zhang F.,Beihang University | Zhang F.,Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology | Cui Y.,Beihang University | Cui Y.,Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology | And 3 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2013

The microstructure, phase transformation and shape memory properties of Ti69Zr30Fe1 high-temperature shape memory alloy were investigated by optical microscopy (OM), X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and compressive tests. The results show that Ti69Zr30Fe1 alloy is composed of single needle-like α″ martensite with orthorhombic structure at room temperature. During heating process, nano scale ω phases precipitate within the grains at 584°C, and then reverse martensitic transformation from α″ phase to β phase occurs at 615~633°C. When cooling, martensitic transformation occurs from 584 to 529°C. The critical stress of Ti69Zr30Fe1 alloy is about 550 MPa and the maximum shape memory effect (SME) is 2.1%. Copyright © 2013, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.


Xin Y.,North China Electrical Power University | Chai L.,Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology
Rare Metals | Year: 2014

Microstructure, martensitic transformation behavior, mechanical and shape memory properties of Ni56-x Mn25Fe x Ga 19 (x = 0, 2, 4, 6, 8) shape memory alloys were investigated using optical microscopy (OM), X-ray diffraction analysis (XRD), differential scanning calorimeter (DSC), and compressive test. It is found that these alloys are composed of single non-modulated martensite phase with tetragonal structure at room temperature, which means substituting Fe for Ni in Ni56Mn 25Ga19 alloy has no effect on phase structure. These alloys all exhibit a thermoelastic martensitic transformation between the cubic parent phase and the tetragonal martensite phase. With the increase of Fe content, the martensitic transformation peak temperature (M p) decreases from 356 C for x = 0 to 20 C for x = 8, which is contributed to the depressed electron concentration and tetragonality of martensite. Fe addition remarkably reduces the transformation hysteresis of Ni-Mn-Ga alloys. Substituting Fe for Ni in Ni56Mn25Ga19 alloy can decrease the strength of the alloys and almost has no influence on the ductility and shape memory property. © 2013 The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg.


Xin Y.,North China Electrical Power University | Chai L.,Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology
Beijing Keji Daxue Xuebao/Journal of University of Science and Technology Beijing | Year: 2013

The microstructure, martensitic transformation behavior, mechanical properties and shape memory characteristics of Ni56Mn25-xFexGa19 (x=0-10) shape memory alloys were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, differential scanning calorimetry, and compression testing. A single phase of martensite with tetragonal structure is observed in the alloys with x≤4, but dual phases with martensite and face-centered cubic γ phase are present when x≥6. Compared with martensite phase, γ phase is rich in Ni and Fe, and its volume fraction increases with increasing Fe content. The martensitic transformation peak temperature decreases from 356°C for x=0 to 170°C for x=10, which is attributed to the comprehensive effect of the tetragonality and electron concentration of martensite. The introduction of ° phase by substituting Fe for Mn can greatly improve the strength and plasticity of the alloys. However, the shape memory strain drops from 5.0% for x=0 to 2.0% for x=6.

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