Structural study and evaluation of thermoelectric properties of single-phase isocubanite (CuFe₂S₃) synthesized via an ultra-fast efficient microwave radiation technique

Abstract

The current state-of-the-art thermoelectric materials are generally composed of expensive, scarce, and toxic elements. In this respect, copper-based sulfide compounds have emerged as viable alternatives. Herein, we report for the...

In situ thermo‐Raman spectroscopy and ab initio vibrational assignment calculations of cubanite CuFe2S3

“…[51][52][53] 3.5 | T = 443-513 K (isocubanite phase) At $443 K, the spectrum of orthorhombic cubanite is abruptly transformed into the spectrum of cubic isocubanite, which is characterized by three vibrational modes with peaks at $282, 312, and 327 cm À1 at $443 K, and is accompanied by a change in the electronic structure. 54 The obtained spectrum of isocubanite is similar to that for isocubanite R090050 presented in the RRUFF.info database. The phase transition according to the Raman data is recorded at $443 K, which differs significantly from the literature data, according to which the transition temperature is $523 K (or $548 K).…”

Tin-Substituted Chalcopyrite: Ann-Type Sulfide with Enhanced Thermoelectric Performance

“…To the best of our knowledge, the carrier mobility of isocubanite has not been reported. However, the lower reported resistivity and Seebeck coefficient of this phase suggests that the mobility is appreciably higher than that of chalcopyrite: a view that is supported by the DFT calculations of Barbier et al 57 , 58 Therefore, the presence of appreciable amounts of isocubanite at x > 0.05 may contribute to the observed marked increase in the charge-carrier mobility at higher levels of tin substitution. Similar increases in mobility on introduction of a higher mobility phase have been reported in nanocomposites of thermoelectrics.…”

“…For higher levels of substitution ( x ≥ 0.05), κ L decreases further through a combination of these effects and the increased amount of impurity phases. The thermal conductivity of isocubanite, identified by powder X-ray diffraction, is somewhat lower than that of chalcopyrite (κ L ≈ 3.6 to 2.5 W m –1 K –1 over the range 323 ≤ T /K ≤ 673) , and therefore contributes to the reduction in thermal conductivity of the more highly substituted materials. Moreover, for materials with x > 0.05, the microstructure consists of a high concentration of pores and microcracks.…”

“…This enables a relatively high value of the Seebeck coefficient, albeit reduced from that of the end-member phase, to be maintained for levels of tin incorporation of x ≤ 0.04. Above this value, the isocubanite impurity, which has a much lower Seebeck coefficient ( S = −65 to −75 μV K –1 at 323 ≤ T /K ≤ 723 , significantly reduces the measured Seebeck coefficient of Cu 1‑ x Sn x FeS 2 (0.05 ≤ x ≤ 0.1). Therefore, although it has been predicted that very high charge- carrier concentrations (ca.…”

“…Materials with higher levels of tin incorporation contain increasing amounts of the isocubanite (CuFe 2 S 3 ) phase as evidenced by X-ray diffraction. Since the electrical resistivity of isocubanite is an order of magnitude lower (ρ ≈ 0.01 mΩ m at 323 ≤ T /K ≤ 723) , than that of the Cu 1‑ x Sn x FeS 2 phases, it has an increasingly marked impact on electrical transport properties, effectively decreasing the overall electrical resistivity and significantly modifying its temperature dependence.…”