Transport property measurements in tungsten sulphoselenide single crystals grown by a CVT technique

Solanki, G. K.; Gujarathi, D. N.; Deshpande, M. P.; Lakshminarayana, D.; Agarwal, M. K.

doi:10.1002/crat.200711060

Cited by 36 publications

(32 citation statements)

References 29 publications

(24 reference statements)

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“…a of pure WS 2 was 654 mV K À1 which is consistent with the values in the literature. 10,13,14 The positive value confirms the p-type characteristic of the specimen. The temperature difference varied between 0.5 and 3.5 C during the measurements of a, and there was a linear relationship between the generated voltage and temperature difference (see Fig.…”

supporting

confidence: 72%

Enhanced thermoelectric properties of tungsten disulfide-multiwalled carbon nanotube composites

Suh¹,

Lee²,

Kang³

et al. 2012

J. Mater. Chem.

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We investigated WS 2 -multiwalled carbon nanotube composites prepared by powder metallurgy. The inclusion of a small amount of nanotubes (0.75 wt%) dramatically increased electrical conductivity (by 12 300%) with a moderate decrease in the Seebeck coefficient (by 22%) and thermal conductivity (by 43%) enhancing both power factor and thermoelectric figure of merit at 300 K.Thermoelectric materials, which allow direct conversion between thermal energy and electricity, have received considerable attention recently as an eco-friendly energy transformation source. 1 The conversion efficiency is described by the dimensionless thermoelectric figure of merit zT ¼ (a 2 s/k)T where a, k, s, and T are the Seebeck coefficient, thermal conductivity, electrical conductivity, and absolute temperature, respectively. 2 Materials with superior thermoelectric properties typically contain rare and potentially toxic elements such as Te, Sb, Pb, Bi and Se. 3-5 The hybrid composite structures containing these elements have also been actively investigated to enhance thermoelectric performance. 6-8 Therefore, new thermoelectric materials are of interest due to the toxicity and abundance issues. Tungsten disulfide (WS 2 ), a layered transition metal dichalcogenide, is a promising candidate since it is an environmentally friendly and abundant material. 5,9-12 It also has a high a ($375 to 1000 mV K À1 ) 10,13,14 and low k ($1.1 to $2.25 W m À1 K À1 ). 14,15 However, s is nearly 3-6 orders of magnitude lower ($10 À1 to $10 1 S m À1 ) than those of binary tellurides resulting in a very low power factor (sa 2 ) and zT. 8,10,13-16 Here we have investigated WS 2 -multiwalled carbon nanotube (MWNT) composites, prepared by powder metallurgy, over a wide range of temperatures (300-800 K). The inclusion of a small amount of nanotubes with high aspect ratios (0.75 wt%) dramatically increased both carrier concentration (by 8670%) and electrical conductivity (by 12 300%) at room temperature. There was a moderate decrease in the Seebeck coefficient by 22%. Interestingly, the thermal conductivity was reduced by 43% probably due to the increase in the grain boundary and interface scattering of phonons. This increased both power factor (68.4 mW m À1 K À2 ) and thermoelectric figure of merit (0.0063) at 300 K by 7330 and 13 100%. The thermoelectric performance increased with increasing temperature. The maximum power factor and thermoelectric figure of merit were 390 mW m À1 K À2 and 0.22 at 700-800 K respectively.Recently, substantial amounts of single-walled carbon nanotubes (SWNTs) (10-100 wt%) were mixed with exfoliated WS 2 to synthesize freestanding WS 2 -SWNT hybrid films by a vacuum filtration method. 15 The s could be increased in the hybrid films ($10 4 S m À1 ). However, a was significantly reduced (60-80 mV K À1 ) 15 and k was increased compared with the pure WS 2 specimens. 14,15 The addition of nanotubes increased the power factor faster than k leading to an increase in zT. However, the maximum power factor ($120 mW m À1 K À2 ) and zT ($0.001)...

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supporting

confidence: 72%

Enhanced thermoelectric properties of tungsten disulfide-multiwalled carbon nanotube composites

Suh¹,

Lee²,

Kang³

et al. 2012

J. Mater. Chem.

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“…Owing to the superior σ at comparable |S|, the power factor of the 2D monolayers is one order of magnitude larger than that of the 3D bulks, which is good agreement with [36][37][38][39][40][41]. (b) The power factor vs σ is exhibited for reported bulks (gray area) and large-area monolayers (green area) [36][37][38][39][40][41]. A significant enhancement in the 2D monolayer forms results in a power factor that is one order of magnitude larger than that in the 3D bulk forms.…”

mentioning

confidence: 64%

“…The comparison between large-area 2D monolayers and 3D bulks is summarized in Figs. 3(a) and 3(b), representing various semiconducting TMDC bulks, MoS 2 monolayers, and WSe 2 monolayers by black, blue, and red symbols, respectively [36][37][38][39][40][41]. We selected only large-area samples and excluded tiny single-crystal films.…”

mentioning

confidence: 99%

Enhanced thermoelectric power in two-dimensional transition metal dichalcogenide monolayers

Kanahashi

Cuong

et al. 2016

Phys. Rev. B

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The carrier-density-dependent conductance and thermoelectric properties of large-area MoS 2 and WSe 2 monolayers are simultaneously investigated using the electrolyte gating method. The sign of the thermoelectric power changes across the transistor off-state in the ambipolar WSe 2 transistor as the majority carrier density switches from electron to hole. The thermopower and thermoelectric power factor of monolayer samples are one order of magnitude larger than that of bulk materials, and their carrier-density dependences exhibit a quantitative agreement with the semiclassical Mott relation based on the two-dimensional energy band structure, concluding the thermoelectric properties are enhanced by the low-dimensional effect.

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“…where μ is the mobility. Then, Equation (3) can be rewritten as [22][23][24]: According to above equation, the Seebeck coefficient of a semiconductor strongly depends on the electrical conductivity. It seems that the electrical transport properties of the materials can be modified via controlling their microstructures using the fabrication conditions.…”

Section: Thermoelectric Performancementioning

confidence: 99%

Study of Conventional Sintered Cu2Se Thermoelectric Material

2019

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Lead-free thermoelectric material, copper chalcogenides, have been attracting much interest from many research and industrial applications owing to their high capability of harvesting energy from heat. The state-of-the-art copper chalcogenides are commonly fabricated by the spark plasma sintering (SPS) and hot pressing (HP) techniques. Those methods are still costly and complicated particularly when compared to the conventional solid-state sintering method. Here, we report an easy-to-fabricate lead-free copper(I)-selenium (Cu 2 Se) that was fabricated using the conventional sintering method. The fabrication conditions, including sintering temperature and dwelling time, have been systematically studied to optimize the thermoelectric performance of Cu 2 Se. The optimized zT value for the pure Cu 2 Se was found to be 1.2 for the sample sintered at 1173 K for 2 h. The study shows that Cu 2 Se developed using the simple and low-cost techniques could exhibit comparable thermoelectric performance when compared with those fabricated by the SPS method, which provides an alternative potential technique to synthesize high-performance thermoelectric materials in a cost-effective way for industrialization.

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Transport property measurements in tungsten sulphoselenide single crystals grown by a CVT technique

Cited by 36 publications

References 29 publications

Enhanced thermoelectric properties of tungsten disulfide-multiwalled carbon nanotube composites

Enhanced thermoelectric properties of tungsten disulfide-multiwalled carbon nanotube composites

Enhanced thermoelectric power in two-dimensional transition metal dichalcogenide monolayers

Study of Conventional Sintered Cu2Se Thermoelectric Material

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