Effect of mixed occupancies on the thermoelectric properties of BaCu_6−xSe_1−yTe_6+y polychalcogenides

Abstract

Increasing the Te amount, y in BaCu6−xSe1−yTe6+y, causes higher electrical conductivity by increasing the Cu deficiencies for steric reasons.

Thermoelectric Properties of Hot-Pressed Ba3Cu14−δTe12

“…More specifically, other copper chalcogenides have also exhibited electrical conductivity values between 100 and 700 Ω –1 cm –1 . Our electrical conductivity values were comparable to those of Cu 2 Se (σ = 750 to 250 Ω –1 cm –1 from 300 to 900 K) but higher than those of the polychalcogenide BaCu 5.9 SeTe 6 (σ = 250 to 150 Ω –1 cm –1 from 300 to 575 K) and the high-performance tetrahedrite Cu 10.5 NiZn 0.5 Sb 4 S 13 (σ = 130 to 180 Ω –1 cm –1 from 300 to 700 K) …”

“…Typically, high-performance p-type thermoelectric materials exhibit thermopower values well in excess of 50 μV K –1 . While the highest thermopower obtained here was 60 μV K –1 at 570 K, this value was still lower than that of most advanced p-type thermoelectric materials such as Cu 2 Se (75–250 μV K –1 at 300–900 K), BaCu 5.9 SeTe 6 (150–225 μV K –1 at 300–575 K), and Cu 10.5 NiZn 0.5 Sb 4 S 13 (150–200 μV K –1 at 300–700 K) . Thus, further attempts to enhance the Seebeck coefficient of Ba 3 Cu 14−δ Te 12 are required for this material to become competitive.…”

“…Overall, the thermal conductivity values obtained for all the materials studied were very low, i.e., mostly below 1 W m –1 K –1 . Thus, the thermal conductivity values of Ba 3 Cu 14−δ Te 12 were on the order of those of high-performance copper chalcogenides such as Cu 2 Se (from 1.2 to 0.6 W m –1 K –1 from 300 to 900 K), BaCu 5.9 SeTe 6 (from 0.85 to 0.5 W m –1 K –1 from 300 to 575 K), and Cu 10.5 Ni 0.5 Sb 4 S 13 (from 0.5 to 0.55 W m –1 K –1 from 300 to 700 K) …”

Quasi-layered Crystal Structure Coupled with Point Defects Leading to Ultralow Lattice Thermal Conductivity in n-Type Cu2.83Bi10Se16

“…Achieving ultralow lattice thermal conductivity has been demonstrated to be an efficient way to increase the thermoelectric figure of merit, zT , driving intensive research efforts on complex structure compounds with intrinsically low lattice thermal conductivity. − The race for the lowest k L in crystalline solids is not only crucial to develop emerging thermoelectric materials but also fundamentally important to the condensed matter physics discipline. One efficient way to reduce k L is through crystal structure engineering (e.g., filler atoms in cage-structures, vacancies, mixed-occupancy, − anti-site defects, , etc.). In this work, reduced k L is achieved through splitting and partial filling of atomic sites in a complex quasi-layered material, Cu 2.83 Bi 10 Se 16 .…”

Stability and Thermoelectric Properties of the Canfieldite Ag8SnS6

“…Materials such as Cu 2– x Q , and Ag 2 Se , are examples of superionic conductors with extremely low thermal conductivity, and zT values often exceeding unity. Although superionic conductors have desirable thermoelectric properties, the instability and degradation due to the highly mobile Cu + /Ag + ions have hindered the utilization of these materials. , Efforts to enhance the stability of these materials include the introduction of heavy or immobile cations to block the movement of ions (diffusion barriers), as well as exploring the usage of safe operating temperatures and electrical currents. − In some cases, the addition of immobile cations created additional deficiencies causing enhanced stability. , …”