Pb_mBi₂S_3+m Homologous Series with Low Thermal Conductivity Prepared by the Solution-Based Method as Promising Thermoelectric Materials

Abstract

Homologous compounds with complex crystal structures are considered as a new class of potential thermoelectric materials due to the possible low thermal conductivity. The thermoelectric properties of Pb m Bi2S3+m (m = 0, 1, and 3) homologous series are investigated in the temperature range of 300–800 K. The samples are prepared by a solution-based method assisted with EDTA-2Na in aqueous media, followed by sintering at 973 K. All obtained Pb m Bi2S3+m show an N-type degenerate semiconducting behavior, providing thermoelectric power factors, PF, of 3.7 μW·cm–1·K–2 for PbBi2S4 and 2.5 μW·cm–1·K–2 for Pb3Bi2S6 at 800 K. Meanwhile, very low thermal conductivities, κtotal, ranging from 0.55 to 0.65 and 0.93 to 1.17 W·m–1·K–1 are achieved at 300–800 K for PbBi2S4 and Pb3Bi2S6, respectively. Significantly, both PbBi2S4 and Pb3Bi2S6 reveal extremely low lattice thermal conductivities, κLat, of less than 0.46 and 0.79 W·m–1·K–1 over the entire temperature range, respectively. As a result, the highest thermoelectric figure of merit zT of 0.46 at 800 K is observed in PbBi2S4 due to a higher power factor and lower thermal conductivity compared with Pb3Bi2S6.

A Tunable Structural Family with Ultralow Thermal Conductivity: Copper-Deficient Cu1–x□xPb1–xBi1+xS3

“…Such a large value, close to those reported for other ultralow- κ L materials (Table ), is consistent with strong phonon–phonon scattering in CuPbBi 5 S 9 . Similar characteristics have been observed in the phonon spectra of the aforementioned chainlike and sulfide compounds, all of them exhibiting ultralow κ L values. − The presence of soft bonding interactions in CuPbBi 5 S 9 is further supported by the low average sound velocity v s of 1758 m s –1 (see eq S4), which is comparable to published data on CuPbBi 5 S 9 and to those of other low-thermal-conductivity chalcogenides (Table ).…”

“…Similar characteristics have been observed in the phonon spectra of the abovementioned chain-like and sulfide compounds, all of them exhibiting ultralow L. [79][80][81][82][83] The presence of soft bonding interaction in CuPbBi5S9 is further supported by the low average sound velocity vs of 1758 m s -1 (see eq. S4), which is comparable with published data 39…”

“…(Top panel) ZT and (bottom panel) lattice thermal conductivity in state of the art thermoelectric n - type Bi-based sulfides. − ,,,,− The values inside the histogram bars are the carrier concentrations.…”

“…optimum S values predicted in several studies, 85,87,88 shows that the carrier concentration should be further increased using other aliovalent substitutions. [33][34][35]37,38,83,[89][90][91] The values inside the histogram bars are the carrier concentration.…”

Nanocrystal Heterostructures Based On Halide Perovskites and Lead–Bismuth Chalcogenides

“…With both lead and bismuth being isoelectronic and active species in the reaction mixture, our synthesis gives access to compounds within the ternary PbS–Bi 2 S 3 system for the domain grown on the perovskite seed. Compounds in this PbS–Bi 2 S 3 system have been investigated as NCs and in bulk for their thermoelectric properties, , but the variation of the composition might also allow a facile tuning of the band gap. , In essence, the introduction of bismuth results in the formation of NC heterostructures made of two domains: a prismatic CsPbBr 3 perovskite domain and an elongated Pb x Bi y S z chalcogenide domain. These NC heterostructures are investigated by advanced electron microscopy to identify their three-dimensional shape, and the progress of the reaction is followed by in situ and ex situ experiments to investigate their formation.…”