排序方式: 共有33条查询结果,搜索用时 15 毫秒
1.
在GeTe-Bi2Te3赝二元系统中, (GeTe)n(Bi2Te3)m化合物往往具有较低的晶格热导率, 但其中很多组分的热电性能尚未得到系统研究。本研究通过熔融、淬火、退火结合放电等离子烧结工艺制备了一系列(GeTe)nBi2Te3(n=10, 11, 12, 13, 14)单相多晶样品, 并对其相组成和热电性能进行表征和研究。掺杂Bi2Te3可以显著增强点缺陷声子散射, 大幅度降低材料的晶格热导率, 在723 K时, (GeTe)13Bi2Te3样品的总热导率低至1.63 W?m -1?K -1。此外, 掺杂Bi2Te3和调控GeTe的相对含量, 提高了材料的载流子有效质量, 即使在较高的载流子浓度下, 样品依然保持较高的塞贝克系数和功率因子, 在723 K, (GeTe)13Bi2Te3样品获得最大的功率因子为2.88×10 -3 W?m -1?K -2, 最终(GeTe)13Bi2Te3样品在723 K获得的最大ZT值达到1.27, 较未掺杂的GeTe样品提高了16%。 相似文献
2.
S. N. Zhang J. He X. H. Ji Z. Su S. H. Yang T. J. Zhu X. B. Zhao Terry M. Tritt 《Journal of Electronic Materials》2009,38(7):1142-1147
Inspired by the high ZT value lately attained in Ar-protected ball-milled nanocrystalline p-BiSbTe bulk alloy, we report herein an investigation of the effects of ball-milling atmosphere on the thermoelectric (TE)
properties of the traditional TE material (GeTe)85(AgSbTe2)15 (TAGS-85). TAGS-85 samples were prepared via a melting–quenching–annealing process, and then ball-milled in different atmospheres
and subsequently densified using a spark plasma sintering technique. The Seebeck coefficient, electrical conductivity, thermal
conductivity, and Hall coefficient were measured as a function of temperature from 10 K to 310 K. It was found that different
ball-milling atmospheres, i.e., air, liquid N2 (LN2), and Ar, profoundly affected the TE properties. A state-of-the-art figure of merit ZT ≈ 0.30 was attained at 310 K in the Ar-ball milled sample. The results are discussed in terms of the carrier concentration,
mobility, crystallinity, and the grain boundary scattering. 相似文献
3.
Y. Gelbstein O. Ben-Yehuda E. Pinhas T. Edrei Y. Sadia Z. Dashevsky M. P. Dariel 《Journal of Electronic Materials》2009,38(7):1478-1482
The search for alternative energy sources is presently at the forefront of␣applied research. In this context, thermoelectricity
for direct energy conversion from thermal to electrical energy plays an important role. This␣paper is␣concerned with the development
of highly efficient p-type [(PbTe)(SnTe)(Bi2Te3)]
x
(GeTe)1−x
alloys for thermoelectric applications using spark plasma sintering (SPS). Varying the carrier concentration of GeTe was
achieved by alloying of PbTe, SnTe, and/or Bi2Te3. The rhombohedral to cubic phase transition temperature, T
c, was found to be sensitive to the degree of alloying. Highest power factor values (P ≤ 33 μW/cm K2) were obtained for (GeTe)0.95(Bi2Te3)0.05 composition. 相似文献
4.
GeTe is an interesting material presenting both spontaneous polarization (ferroelectrics) and outstanding electrical conductivity (ideal for thermoelectrics). Pristine GeTe exhibits classic 71° and 109° submicron ferroelectric domains, and near unity thermoelectric figure of merit ZT at 773 K. In this work, it is demonstrated that Bi2Te3 alloying in GeTe lattice can introduce vast Ge vacancies which can further evolve into nanoscale van der Waals gaps upon proper heat treatment, and that these vacancy gaps can induce 180° nanoscale ferroelectric domain boundaries. These microstructures eventually become a hierarchical ferroelectric domain structure, with size varying from submicron to nanoscale and polarization from 71°, 109° to 180°. The establishment of hierarchical ferroelectric domain structure, together with the nanoscale Ge vacancy van der Waals gaps, has profound effects on the electrical and thermal transport properties, resulting in a striking peak thermoelectric ZT ≈ 2.4 at 773 K. These findings might provide an alternative conception for thermoelectric optimization via microstructure modulation. 相似文献
5.
Peigen Li Teng Ding Junqin Li Chunxiao Zhang Yubo Dou Yu Li Lipeng Hu Fusheng Liu Chaohua Zhang 《Advanced functional materials》2020,30(15)
Because the intrinsic Ge vacancies in GeTe usually lead to high hole concentration beyond the optimal range, many previous studies tend to consider Ge vacancies as negative effects on increasing the figure of merit ZT of GeTe‐based alloys, and consequently have proposed various approaches to suppress Ge vacancies. However, in this work, it is demonstrated that the Ge vacancies can have great positive effects on enhancing the ZT of GeTe‐based alloys when the hole concentration falls into the optimal range. First, hole concentration of GeTe is reduced close to the optimal range by co‐alloying of Pb and Bi, and then the Ge vacancies are increased by adding excess Te into the Ge0.8Pb0.1Bi0.1Te1+x. The Ge vacancies can cause lattice shrinkage and promote rhombohedral‐to‐cubic phase transition. As revealed by first‐principle calculations, theoretical simulations, and experimental tests, Ge vacancies can facilitate the band convergence, suppress the bipolar transport at higher temperature range, and reduce the lattice thermal conductivity. Combining these effects, a peak ZT of 1.92 at 637 K and an average ZT of 1.34 within 300–773 K in Ge0.8Pb0.1Bi0.1Te1.06 can be obtained, demonstrating the great significance of utilizing vacancy‐type defects for enhancing ZT. 相似文献
6.
Yu Wang Cong Wang Shi-Jun Liang Zecheng Ma Kang Xu Xiaowei Liu Lili Zhang Alemayehu S. Admasu Sang-Wook Cheong Lizheng Wang Moyu Chen Zenglin Liu Bin Cheng Wei Ji Feng Miao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(42):2004533
By virtue of the layered structure, van der Waals (vdW) magnets are sensitive to the lattice deformation controlled by the external strain, providing an ideal platform to explore the one-step magnetization reversal that is still conceptual in conventional magnets due to the limited strain-tuning range of the coercive field. In this study, a uniaxial tensile strain is applied to thin flakes of the vdW magnet Fe3GeTe2 (FGT), and a dramatic increase of the coercive field (Hc) by more than 150% with an applied strain of 0.32% is observed. Moreover, the change of the transition temperatures between the different magnetic phases under strain is investigated, and the phase diagram of FGT in the strain–temperature plane is obtained. Comparing the phase diagram with theoretical results, the strain-tunable magnetism is attributed to the sensitive change of magnetic anisotropy energy. Remarkably, strain allows an ultrasensitive magnetization reversal to be achieved, which may promote the development of novel straintronic device applications. 相似文献
7.
8.
The optical parameters of GeTe semiconductor films after various thermal treatments have been measured using a novel method. A comparative study using a spectrum ellipsometer is presented. The optical parameters of the films were extracted precisely by data analysis and corrections have been made to previous calculations. Calculations based on the spectral ellipsometry measurements are presented finally, and the complex refractive index curves of the samples in the spectral range from 250 to 830 nm have been obtained. 相似文献
9.
Enhancement of thermopower is achieved by doping the narrow‐band semiconductor Ag6.52Sb6.52Ge36.96Te50 (acronym TAGS‐85), one of the best p‐type thermoelectric materials, with 1 or 2% of the rare earth dysprosium (Dy). Evidence for the incorporation of Dy into the lattice is provided by X‐ray diffraction and increased orientation‐dependent local fields detected by 125Te NMR spectroscopy. Since Dy has a stable electronic configuration, the enhancement cannot be attributed to 4f‐electron states formed near the Fermi level. It is likely that the enhancement is due to a small reduction in the carrier concentration, detected by 125Te NMR spectroscopy, but mostly due to energy filtering of the carriers by potential barriers formed in the lattice by Dy, which has large both atomic size and localized magnetic moment. The interplay between the thermopower, the electrical resistivity, and the thermal conductivity of TAGS‐85 doped with Dy results in an enhancement of the power factor (PF) and the thermoelectric figure of merit (ZT) at 730 K, from PF = 28 μW cm?1 K?2 and ZT ≤ 1.3 in TAGS‐85 to PF = 35 μW cm?1 K?2 and ZT ≥ 1.5 in TAGS‐85 doped with 1 or 2% Dy for Ge. This makes TAGS‐85 doped with Dy a promising material for thermoelectric power generation. 相似文献
10.
Trinh Thi Ly Jungmin Park Kyoo Kim Hyo-Bin Ahn Nyun Jong Lee Kwangsu Kim Tae-Eon Park Ganbat Duvjir Nguyen Huu Lam Kyuha Jang Chun-Yeol You Younghun Jo Se Kwon Kim Changgu Lee Sanghoon Kim Jungdae Kim 《Advanced functional materials》2021,31(17):2009758
Microscopic structures and magnetic properties are investigated for Fe5−xGeTe2 single crystal, recently discovered as a promising van der Waals (vdW) ferromagnet. An Fe atom (Fe(1)) located in the outermost Fe5Ge sublayer has two possible split-sites which are either above or below the Ge atom. Scanning tunneling microscopy shows √3 × √3 superstructures which are attributed to the ordering of Fe(1) layer. The √3 × √3 superstructures have two different phases due to the symmetry of Fe(1) ordering. Intriguingly, the observed √3 × √3 ordering breaks the inversion symmetry of crystal, resulting in substantial antisymmetric exchange interaction. The temperature dependence of magnetization reveals a sharp magnetic anomaly suggesting helical magnetism of the Fe5−xGeTe2 due to its non-centrosymmetricity. Analytical study also supports that the observed ordering can give rise to the helimagnetism. The work will provide essential information to understand the complex magnetic properties and the origin of the new vdW ferromagnet, Fe5−xGeTe2 for future topology-based spin devices. 相似文献