Thermoelectric properties in the series Ti1-xTaxS2

Abstract

Polycrystalline samples in the series Ti1-xTaxS2 with x varying from 0 to 1 were prepared using solid-liquid-vapor reaction and spark plasma sintering. Rietveld refinements of X-ray diffraction data are consistent with the existence of a full solid solution for x ≤ 0.4. Transport measurements reveal that tantalum can act as electron donor when substituted in the Ti sites. As a consequence, the electrical resistivity and the absolute value of the Seebeck coefficient decrease with Ta content due to an increase in the carrier concentration. The lattice thermal conductivity being reduced due to mass fluctuation effect, the ZT values in Ti0.95Ta0.05S2 is slightly increased as compared to TiS2.

Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides

“…In the case of TiS 2 -based layered sulfides, a single crystal can be grown using the chemical-vapor-transport method with I 2 as the transport agent [38,39,40,41]. Polycrystalline TiS 2 -based layered sulfides have been commonly prepared by melting stoichiometric amounts of the constituent elements in evacuated and sealed quartz tubes at 905–1273 K, followed by pressurized sintering at 873–1173 K [30,42,43,44,45,46,47]. However, these methods are difficult to apply because of the large difference in vapor pressure between metals and sulfur; consequently, there is less motivation for researchers in the thermoelectric community to investigate thermoelectric sulfides further.…”

“…Because TiS 2 -based layered sulfides are primarily composed of earth-abundant, low-toxicity, and light elements, they will pave the way for environment-friendly, cost-effective, and lightweight thermoelectric devices [29,30,39,40,41,42,43,44,45,46,47,56,57,58,59,60,61,62,63,64,65,66]. The two-dimensional crystal structure of these systems is a great example in which the thermoelectric performance can be improved through nanoblock integration and hierarchical architecturing.…”

“…Temperature dependence of the thermoelectric figure of merit ( ZT ) in the in-plane ( ab -plane) direction for single-crystal TiS 2 [40] and polycrystalline Ti 1.008 S 2 [29], Ti 1.025 S 2 [30], Cu 0.1 TiS 2 [44], TiS 1.5 Se 0.5 [45], Ti 0.95 Ta 0.05 S 2 [46], [BiS] 1.2 [TiS 2 ] 2 [42], [PbS] 1.18 [TiS 2 ] 2 [42], [SnS] 1.2 [TiS 2 ] 2 [43], and [BiS] 1.2 [Ti 0.95 Cr 0.05 S 2 ] 2 [66]. …”

“…For example, Cu intercalation reduces κ lat from ~2.0 W·K −1 ·m −1 for TiS 2 to ~1.7 W·K −1 ·m −1 for Cu 0.1 TiS 2 , and SnS intercalation dramatically reduces κ lat to ~1.0 W·K −1 ·m −1 for [SnS] 1.2 [TiS 2 ] 2 at 300 K (Figure 7a). Substitution is another way to reduce κ lat [45,46,47]; for example, the substitution of Ti by Ta slightly reduces κ lat to ~1.8 W·K −1 ·m −1 for Ti 0.95 Ta 0.05 S 2 at 300 K (Figure 7b).…”

“…Temperature dependence of the lattice thermal conductivity (κ lat ) in the in-plane ( ab -plane) direction for Ti 1.008 S 2 [29]: ( a ) intercalated systems [BiS] 1.2 [TiS 2 ] 2 [42], [PbS] 1.18 [TiS 2 ] 2 [42], [SnS] 1.2 [TiS 2 ] 2 [43], and Cu 0.1 TiS 2 [44]; ( b ) substituted systems TiS 1.5 Se 0.5 [45] and Ti 0.95 Ta 0.05 S 2 [46]. …”