Synthesis and physical properties of single-crystalline InTe: towards high thermoelectric performance

Abstract

Chalcogenide semiconductors and semimetals continue to be of prime interest for thermoelectric applications in power generation. As another representative of this broad class of materials, tetragonal InTe has recently emerged...

Controlling Defect Chemistry in InTe by Saturation Annealing

“…Here, we show that this technique can be also applied to single-crystalline and polycrystalline InTe, a chalcogenide semiconductor that has recently emerged as an interesting thermoelectric material due to its extremely low lattice thermal conductivity. − This process, realized on both the In-rich and Te-rich sides of the solidus line at selected temperatures varying between 843 and 943 K, results in hole densities ranging from 4.9 × 10 19 up to 8.5 × 10 19 cm –3 at 300 K. While the results obtained on the In-rich side are consistent with the presence of a small amount of singly charged, acceptor-like In vacancies, the lower hole density achieved for the sample annealed on the Te-rich side suggests the formation of donor-like defects that partially compensate holes. , In spite of the narrow hole concentration range accessible, the low-temperature transport properties markedly vary with the annealing temperature. The ZT values of all saturated samples, that range between 0.7 and 0.8 around 770 K, are slightly lower than the peak ZT achieved in as-synthesized InTe (0.9 at 710 K) due to their increased degenerate character.…”

“…All samples display a similar microstructure (Figure S3 in the SI), with grains formed by stacked plate-like InTe layers. This layer-like structure originates from the (In 3+ Te 4 2 ) − tetrahedra chains weakly bounded to each other that lead to easy cleavage along the (110) plane in single-crystalline InTe. ,, This characteristic explains the anisotropic transport properties observed in polycrystalline and single-crystalline samples. − …”

Local-Disorder-Induced Low Thermal Conductivity in Degenerate Semiconductor Cu22Sn10S32

“…These remarkably low values are similar to those inferred in prior studies for disordered Cu–Sn–S phases , and in other S-based compounds such as tetrahedrites or strongly disordered colusites. − At high temperatures, the κ L values even drop below the minimum lattice thermal conductivity κ min of 0.70 W m –1 K –1 estimated using the Cahill and Pohl relationship , where V is the average volume per atom, k B is the Boltzmann constant, and v T = 2375 m s –1 and v L = 4597 m s –1 are the room temperature transverse and longitudinal sound velocities of the x = 0.075 sample, respectively. This finding, observed in only a few compounds exhibiting ultralow κ L , , suggests that the high-temperature lower bound might be better described by atomic vibrations carrying heat by diffusion. In this diffusive regime, the limit κ diff is given by the expression , yielding κ diff ≈ 0.45 W m –1 K –1 , that is, below the inferred κ L values …”

“…L , where V is the average volume per atom, k B is the Boltzmann constant, and v T = 2375 m s −1 and v L = 4597 m s −1 are the room temperature transverse and longitudinal sound velocities of the x = 0.075 sample, respectively. This finding, observed in only a few compounds exhibiting ultralow κ L , 51,52 suggests that the hightemperature lower bound might be better described by atomic vibrations carrying heat by diffusion. In this diffusive regime, t h e l i m i t κ d i f f i s g i v e n b y t h e e x p r e s s i o n…”

“…This finding, observed in only few compounds exhibiting ultralow 𝜅 ! , 51,52 suggests that the high-temperature lower bound might be better described by atomic vibrations carrying heat by diffusion. In this diffusive regime, the limit 𝜅 0+11 is given by the expression…”