N-Type Thermoelectric AgBiPbS₃ with Nanoprecipitates and Low Thermal Conductivity

Abstract

Thermoelectric sulfide materials are of particular interest due to the earth-abundant and cost-effective nature of sulfur. Here, we report a new n-type degenerate semiconductor sulfide, AgBiPbS3, which adopts a Fm3̅m structure with a narrow band gap of ∼0.32 eV. Despite the homogeneous distribution of elements at the scale of micrometer, Ag2S nanoprecipitates with dimensions of several nanometers were detected throughout the matrix. AgBiPbS3 exhibits a low room-temperature lattice thermal conductivity of 0.88 W m–1 K–1, owing to the intrinsic low lattice thermal conductivity of Ag2S and the effective scattering of phonons at nanoprecipitate boundaries. Moreover, compared to AgBiS2, AgBiPbS3 demonstrates a significantly improved weighted mobility of >16 cm2 V–1 s–1 at 300 K, leading to an enhanced PF of 1.6 μW cm–1 K–2 at 300 K. The superior electrical transport in AgBiPbS3 can be attributed to the high valley degeneracy of the L point (the conduction band minimum), which is contributed by the Pb s and Pb p orbitals. Further, Ga doping is found to be effective in modulating the Fermi levels of AgBiPbS3, leading to further enhancement of PF with a PFave of 2.7 μW cm–1 K–2 in the temperature range of 300–823 K. Consequently, a relatively high ZTave of 0.22 and a peak ZT of ∼0.4 at 823 K have been achieved in 3% Ga-doped AgBiPbS3, highlighting the potential of AgBiPbS3 as an n-type thermoelectric sulfide.

High Thermoelectric Performance in Rhombohedral GeSe-LiBiTe2

“…The band structure of the rhombohedral phase 28GeSe-4LiBiTe 2 reveals a notably smaller band gap of 0.48 eV (Figure 3a, an enlarged image is shown in Figure S9a) compared to the large band gap of 0.85 eV in pristine Pnmastructured GeSe. 22 For hypothetical rhombohedral phase GeSe, the computed band gap is around 0.46 eV, 40 similar to the value for 28GeSe-4LiBiTe 2 . The congruence in band gaps between rhombohedral phase GeSe and 28GeSe-4LiBiTe 2 implies that this modest band gap is not primarily caused by the introduction of Li, Bi, and Te.…”

“…30−33 ing can stabilize the compound exceptionally well in highsymmetry structures, resulting in low lattice thermal conductivity and improved ZTs. 33−35 This has been evidenced in systems such as AgSbTe 2 -MnTe, 36 SnSe-AgSbTe 2 , 36−38 AgBi-(Se,S) 2 -Pb(Se,S), 39,40 and Cu 2 SnSe 3 -AgGaNa. 41 Previous studies on GeSe have also shown positive results by altering the crystal structure, 42−45 which motivates further investigation into the mechanisms underpinning the structure−performance relationship.…”

“…Beyond the doping method, crystal structure modification by alloying is another effective strategy for enhancing thermoelectric performance since carrier and phonon transport are closely related to the crystal structures. − For example, subtle alterations between the R 3 m and Fm 3 ̅m structures have been shown to play a pivotal role in achieving high ZT s in GeTe and its derivatives. − Furthermore, entropy engineering can stabilize the compound exceptionally well in high-symmetry structures, resulting in low lattice thermal conductivity and improved ZT s. − This has been evidenced in systems such as AgSbTe 2 -MnTe, SnSe-AgSbTe 2 , − AgBi­(Se,S) 2 -Pb­(Se,S), , and Cu 2 SnSe 3 -AgGaNa . Previous studies on GeSe have also shown positive results by altering the crystal structure, − which motivates further investigation into the mechanisms underpinning the structure–performance relationship.…”

Thermoelectrics for nuclear fusion reactors: opportunities and challenges

“…2. Although many of the TE materials can achieve high zT s of >2, such as GeTe, 23–34 PbTe, 35–39 and SnSe, 40–44 and others exhibit peak performances in the medium temperature range (473–973 K), 45–53 such TE materials will not be considered for discussion in this review, as they overlap with the operating temperature range of the much more efficient existing heat cycle of the molten salt coolant. Instead, for reliable performance on the plasma-facing surfaces, one should select from the tried and tested high temperature (873–1273 K) TE materials that have been used or assessed for RTGs in deep space probes, such as Si 1− x Ge x , La 3− x Te 4 and Yb 14 MgSb 11 zintls.…”

High-entropy materials for thermoelectric applications: towards performance and reliability

“…This reduced carrier mobility can be compensated by several mitigating strategies such as (i) controlled doping of HEMs, which can enhance the carrier concentration. 119 (ii) Band structure engineering which may involve adjusting the relative concentrations of the different cationic species to optimize the band alignment and minimize carrier scattering, thus enhancing carrier mobility. (iii) Interface engineering to reduce scattering and improve charge carrier mobility can be an effective strategy by optimizing interfaces between different phases or domains within HEMs.…”