Oxychalcogenides as Thermoelectric Materials: An Overview

Abstract

Thermoelectric materials, which can convert heat into electricity and vice versa, have essential applications in power generation, thermocouples, sensors, and cooling. In the past decade, a lot of research has been devoted to developing various oxide-based thermoelectric materials, for mid- to high-temperature applications, ensuring robustness, long lifetimes, and low production costs. Among these oxide materials, one popular class is oxychalcogenides. A comprehensive discussion on the structural, electronic, and thermoelectric properties of both p-type and n-type oxychalcogenides is presented in this review article. The alternatively stacked conducting and insulating layers in these oxychalcogenides combined with a unique bonding network lead to interesting electronic properties and intrinsically low thermal conductivity. The article focuses primarily on Bi-based oxychalcogenides which have shown relatively good thermoelectric performance in the mid- to high-temperature range, with an elaborate discussion on n-type compositions. Several approaches such as chemical doping, modulation doping, introducing vacancies, band structure engineering, and so forth are summarized, vastly improving the zT in these materials and enabling their potential viability for thermoelectric applications. Finally, we discuss a few strategies as a future direction to further enhance the thermoelectric performance in these oxychalcogenide materials.

Anharmonicity and ultralow thermal conductivity in layered oxychalcogenides BiAgOCh (Ch = S, Se, and Te)

“…Recently, BiCuOSe oxyselenides have acquired ever-increasing attention as very promising thermoelectric materials due to their high value of ZT (1.5 at 900 K) [7][8][9][10][11][12] . The outstanding TE properties could be mainly ascribed to their intrinsically low thermal conductivity of BiCuOSe and its alloys [13][14][15][16][17][18] .…”

Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO3 and La-Doped SrTiO3 Materials: A Density Functional Theory Study

“…Most TE materials currently on the market are alloys containing bismuth, antimony, and tellurium, − which are rare, toxic, and/or expensive. While the highest ZT are currently obtained with chalcogenide TEs, , recent work has shown that metal oxides − such as CaMnO 3 , SrTiO 3 , − M 2 CoO 3 , BaTiO 3 , tungsten bronze, , Bi 2 Sr 2 Co 1.8 O y , In 2 O 3 , and La 1/3 NbO 3 may be promising alternatives to conventional TE materials while being made from cheaper, more earth-abundant, and less toxic materials. , Among the potential oxide TEs, strontium titanate (SrTiO 3 ; STO) shows promise due to its thermal stability at high temperature and tolerance to doping. ,, Bulk SrTiO 3 has a relatively poor ZT , and thus doping has been extensively explored as a possible route to improving its performance with examples including substituting Sr sites with rare-earth elements such as La , and Ti sites with other transition metals such s Nb. − La doping has been shown to promote the formation of A-site vacancies, which both increases the electrical conductivity and decreases the thermal conductivity through enhanced phonon scattering . Doping with La under reducing conditions further leads to the formation of oxygen vacancies, which decreases the thermal conductivity while having minimal impact on the electrical conductivity.…”

Effect of hydrostatic pressure on stereochemically active lone-pair of Bi$_2$O$_2$S

“…We have used DFT-D3 method 28 to capture the weak vdWs interactions. The following plane wave basis orbitals were considered as valence electrons; Bi: 5d 10 ,6s 2 ,6p 3 ; O: 2s 2 ,2p 4 ; and S: 3s 2 ,3p 4 . A kinetic energy cutoff of 600 eV was used for plane wave basis set expansion and a spacing of 2π × 0.025 Å−1 for k-mesh in the irreducible Brillouin zone.…”

“…2,3 Bismuth oxychalcogenides are emerging class of materials due to their outstanding thermeoelectric and opto-electronic properties. 4 In particular, dibismuth dioxychalcogenides, Bi 2 O 2 Ch (Ch = S, Se, Te), their 2D counterparts, [5][6][7] and heterostructures 8 gained tremendous research interest due to their potential applications in thermoelectrics, 4,9,10 ferroelectrics, 11 and optoelectronics. 4,6,[12][13][14] The ternary Bi 2 O 2 Ch systems are synthesized by a solid state reaction of well-known binary thermoelectric bismuth chalcogenides Bi 2 Ch 3 (Ch = S, Se, Te) with Bi 2 O 3 .…”

“…4 In particular, dibismuth dioxychalcogenides, Bi 2 O 2 Ch (Ch = S, Se, Te), their 2D counterparts, [5][6][7] and heterostructures 8 gained tremendous research interest due to their potential applications in thermoelectrics, 4,9,10 ferroelectrics, 11 and optoelectronics. 4,6,[12][13][14] The ternary Bi 2 O 2 Ch systems are synthesized by a solid state reaction of well-known binary thermoelectric bismuth chalcogenides Bi 2 Ch 3 (Ch = S, Se, Te) with Bi 2 O 3 . Bi 2 O 2 S crystallizes in the primitive orthorhombic structure (SG: P nmn, Z=2 formula units (f.u.)…”