High‐Temperature Thermoelectric Properties of Sn‐Doped β‐As₂Te₃

Thermoelectric Properties of the α-As2Te3 Crystalline Phase

“…At this step, the b-phase was obtained. 4 The ingot was subsequently annealed at 613 K for 3 days to finally obtain the pure a-As 2 Te 3 phase. The resulting ingots were ground into micron-sized powders and consolidated by SPS into a 10-mm-diameter cylindrical pellet under a pressure of 50 MPa at a temperature of 613 K for 2 min.…”

“…1 Owing to strong interdependence between the three transport properties, achieving high ZT on a broad temperature range still remains the most challenging aspect in thermoelectricity. 2,3 Recently, the metastable b-As 2 Te 3 phase, isostructural to the state-of-the art Bi 2 Te 3 -based materials, showed an interesting performance upon substitution of Sn for As, with peak ZT around 0.6 at 423 K. 4 However, As 2 Te 3 exists in two crystallographic forms: the rhombohedral b-As 2 Te 3 , which was first obtained at high pressure 5 and then directly synthesized by rapid quenching from the melt, 6,7 and the monoclinic a-As 2 Te 3 . 8 The former transforms into the latter upon heating above 410 K. a-As 2 Te 3 has been scarcely studied from the TE point of view but may show interesting properties at which early studies 9,10 and first-principles calculations hint.…”

High-temperature thermoelectric properties of the β-As2−xBixTe3 solid solution

“…9 Interestingly, both α-As 2 Te 3 and β-As 2 Te 3 phases are semiconductors that meet the aforementioned requirements. [10][11][12][13][14] In particular, they share the remarkable feature of being poor thermal conductors with lattice thermal conductivities well below 1 W m −1 K −1 above 300 K. Maximum ZT values of 0.8 at 523 K and 0.65 at 423 K were achieved in α-As 2 Te 3 and β-As 2 Te 3 , respectively, using the substitution of Sn for As as a tuning parameter of the hole concentration. 10,13 a Author to whom correspondence should be addressed.…”

“…1,2 First reported as a high-pressure phase, 7 polycrystalline samples could be obtained with high purity by conventional melting-quenching techniques allowing for a detailed investigation of its transport properties and of the influence of substitution on either the As or Te site. 10 Our prior work on Sn-substituted β-As 2 Te 3 has provided hints at the presence of defects in this material, 10 akin to the Bi 2 Te 3 -based alloys where defect chemistry plays a central role in determining the thermoelectric performances. 1,2 In addition, this compound has been suggested to harbor topological insulating properties when an uniaxial strain is applied along the c axis, 14,15 which could be experimentally realized by applying either an external pressure or a chemical pressure through substitutions.…”

“…Of note, these values are significantly lower than those measured in Bi 2 Te 3 -based alloys but similar to those achieved in α-As 2 Te 3 or in other chalcogenides. 2,10,[22][23][24][25][26][27] In the parallel direction, κ L approaches the lowest limit of the thermal conductivity (Figure 2(c)) estimated using the model developed by Cahill and Pohl and the measured longitudinal and transverse sound velocities. 13,[28][29][30] Figure 2(d), which shows the variations in temperature of the ZT values, indicates that ZT increases with temperature for all samples.…”