Transport and mechanical property evaluation of (AgSbTe)1−x(GeTe)x (x=0.80, 0.82, 0.85, 0.87, 0.90)

Salvador, James R.; Yang, Jihui; Shi, Xun; Wang, H.; Wereszczak, A. A.

doi:10.1016/j.jssc.2009.05.024

Cited by 75 publications

(82 citation statements)

References 20 publications

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“…As a model system, Ag x Sb x Ge 50-2x Te 50 series, well-known GeTe-based high-efficiency tellurium-antimonygermanium-silver thermoelectric materials (TAGS series) [11][12][13], was used. purity), and Te (Alfa Aesar, 99.9999% purity, product #12607, lot 004).…”

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confidence: 99%

Charge carrier effective mass and concentration derived from combination of Seebeck coefficient andTe125NMR measurements in complex tellurides

Levin

2016

Phys. Rev. B

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Thermoelectric materials utilize the Seebeck effect to convert thermal to electrical energy. The Seebeck coefficient (thermopower), S, depends on the free (mobile) carrier concentration, n, and effective mass, m*, as In some materials the influence of m* on the Seebeck coefficient can be significant and its determination is important for better understanding of thermoelectric materials. 125 Te nuclear magnetic resonance (NMR) [4][5][6][7][8][9] can be used to study complex tellurides and derive the carrier concentration from spin-lattice relaxation time, T 1 . In a theoretical model by Selbach et al. [10], the coefficient of proportionality between T 1 and n, "Bloembergen constant", C B , depends on m*. Hence, if the effective mass in a series of materials is not constant, it can affect C B , and, therefore, the carrier concentration deriving from 125 Te NMR T 1 measurements should be different compared to that obtained if m* is constant.Here it is shown that the combination of the (Table 1) were synthesized by a direct reaction of the constituent elements in 10 mm diameter fused silica ampoules in argon backfilled up to ~17 kPa pressure atmosphere. For synthesis we used Ge (Materion G-1038, 99.999% purity), and Te (Alfa Aesar, 99.9999% purity, product #12607, lot 004). Ampoules with the constituent elements were heated up to 1323 K to melt the constituents, and after ~4 hours the melt was cooled down with the furnace at the rate of 100 K/hour. Each ingot had a mass of 20 g, diameter of 10 mm, length of ~40 mm. Analysis of each material was performed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy, and showed that all materials are nearly single phase; only ~1 at.% Ge is present in the samples matrix due to naturally occurring process of Ge rejection from the melt [8,14]. 125 Te NMR experiments were performed at 126 MHz using a Bruker 400WB spectrometer with TOPSPIN software in a magnetic field of 9.4 T without sample spinning 4 (static regime). Powder samples were prepared from ingots and placed in 4-mm diameter insert. 125 Te NMR spin-lattice relaxation measurements were used to obtain the spin-lattice relaxation time, T 1 , using GeTe as a reference material [5,8]; the uncertainty of T 1 measurements is less than ±0.2 ms [5].More experimental details including pulse sequence for 125 Te NMR can be found in Refs. 5,8,9,14. Samples for the Seebeck coefficient measurements were prepared by cutting the ingot with a diamond saw [9]. The Seebeck coefficient was measured by a LSR-3 measuring system (Linseis Inc.) in a helium atmosphere relative to the Pt legs of a Pt-(Pt+Rh) thermocouple and then the absolute Seebeck coefficient was calculated; the uncertainty of measurements is about ±3% [9]. Table 1). 125 Te NMR spectra for these two materials are shown on inset in Fig. 1(a), demonstrating that signals can be easily detected; spectra for the rest of materials also are located between those for GeTe and TAGS-85.Relaxation curves shown on Fig. 1(a) as well as for ...

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Charge carrier effective mass and concentration derived from combination of Seebeck coefficient andTe125NMR measurements in complex tellurides

Levin

2016

Phys. Rev. B

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“…Therefore, optimal TE materials must feature a high PF and low thermal conductivity. 1 (LAST) [18][19][20][21] and GeTe, called tellurium antimony germanium silver (TAGS) 22,23 and have successfully exhibited enhanced TE performance.…”

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Influence of nanoscale Ag2Te precipitates on the thermoelectric properties of the Sn doped P-type AgSbTe2 compound

et al. 2014

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We report a maximal figure of merit (ZT) value of 1.1 at 600 K was obtained for the sample of which x = 0.03, representing an enhancement greater than 20% compared with a pristine AgSbTe2 sample. This favorable thermoelectric performance originated from the optimal Sn2+ substitution for Sb3+ in AgSbTe2, which not only increased electrical conductivity but also led to a substantial reduction in thermal conductivity that was likely caused by an enhanced phonon-scattering mechanism through the combined effects of lattice defects and the presence of Ag2Te nanoprecipitates dispersed in the matrix.

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“…4(a). This discontinuity in electrical conductivity is owing to the phase transformation of rhomobohedral to cubic polymorphic in general TAGS system [22]. Interestingly, the phase transition regions decreases and moves to lower temperature as the milling time increases.…”

Section: Methodsmentioning

confidence: 98%

Microstructure And Thermoelectric Properties Of Tags-90 Compounds Fabricated By Mechanical Milling Process

Kim¹,

Madavali²,

Hong³

2015

Archives of Metallurgy and Materials

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TAGS-90 compound powder was directly prepared from the elements by high-energy ball milling (HEBM) and subsequently consolidated by a spark plasma sintering (SPS). Effect of milling time on the microstructure and thermoelectric properties of the samples were investigated. The particle size of fabricated powders were decreased with increasing milling time, finally fine particles with ∼1µm size was obtained at 90 min. The SPS samples exhibited higher relative densities (>99%) with fine grain size. X-ray diffraction analysis (XRD) and energy dispersion analysis (EDS) results revealed that all the samples were single phase of GeTe with exact composition. The electrical conductivity of samples were decreased with milling time, whereas Seebeck coefficient increased over the temperature range of RT∼450 • C. The highest power factor was 1.12×10 −3 W/mK 2 obtained for the sample with 90 min milling at 450 • C.

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Transport and mechanical property evaluation of (AgSbTe)1−x(GeTe)x (x=0.80, 0.82, 0.85, 0.87, 0.90)

Cited by 75 publications

References 20 publications

Charge carrier effective mass and concentration derived from combination of Seebeck coefficient andTe125NMR measurements in complex tellurides

Charge carrier effective mass and concentration derived from combination of Seebeck coefficient andTe125NMR measurements in complex tellurides

Influence of nanoscale Ag2Te precipitates on the thermoelectric properties of the Sn doped P-type AgSbTe2 compound

Microstructure And Thermoelectric Properties Of Tags-90 Compounds Fabricated By Mechanical Milling Process

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