CsMBi₃Te₆ and CsM₂Bi₃Te₇ (M = Pb, Sn):  New Thermoelectric Compounds with Low-Dimensional Structures

Abstract

The new materials CsPbBi(3)Te(6) and CsPb(2)Bi(3)Te(7) were discovered through reactions of CsBi(4)Te(6) with PbTe, whereas the isostructural materials CsSnBi(3)Te(6) and CsSn(2)Bi(3)Te(7) were discovered through corresponding reactions with SnTe. The compounds can also be prepared from stoichiometric mixtures of Cs(2)Te, Pb (Sn), Bi, and Te. The crystal structures show a layered architecture of NaCl-type slabs alternating with layers of Cs atoms. This group of compounds offers a new quaternary system, Cs-M-Bi-Te (M = Pb and Sn), available for thermoelectric investigations, including fine-tuning of compositions and doping.

Chemical aspects of the design of thermoelectric materials

“…At the same time, the development of more complex compounds based on CsBi 4 Te 6 by introduction of tin or lead atoms into their structure almost halved their thermopower. 38 The thermal conductivity of CsBi 4 Te 6 was within 1.3 ± 1.8 W m 71 K 71 depending on the nature and degree of alloying, which is worse than expected taking into account that this compound is built of heavy atoms and the volume of its unit cell is very large (3250 # A). Apparently, this can be explained by a substantial contribution of the electronic component to thermal conductivity, which is comparable with the phonon component.…”

Crystal and electronic structure of the red semiconductor Ba4LaSbGe3Se13 comprising the complex anion [Ge2Se7–Sb2Se4–Ge2Se7]14−

“…The inert pair of the Sb III atom is sterically active, as reflected in a severely irregular Se coordination reminiscent of the situation in Sb 2 Se 3 . That Ba 4 LaGe 3 SbSe 13 is an electron-precise compound, according to the ionic formulation (Ba 2+ ) 4 (La 3+ )(Ge 4+ ) 3 Sb 3+ (Se 2À ) 13 , reflects itself in its red color. …”

“…Among the most studied materials in thermoelectric research are ternary and higher antimony chalcogenides [1][2][3][4][5][6][7][8][9][10], bismuth chalcogenides [11][12][13][14][15], and germanium and tin-based clathrates [16][17][18][19]. A particularly well explored family of high-temperature thermoelectrics is (AgSbTe 2 ) 1Àx (GeTe) x (TAGS) [20,21].…”

Superconductivity in the orthorhombic phase of thermoelectric CsPbxBi4−xTe6 with 0.3≤x≤1.0

“…In structural point of view, both CsPbBi 3 Te 6 and CsBi 4 Te 6 possess a "M 4 Te 6 " type of framework, which can be viewed as a fragment excised from NaCl-type structure along the [011] direction with a thickness of four {NaCl} monolayers. [4][5][6][7] The CsBi 4 Fig. 1(a).…”

“…Furthermore, our investigations also show that the superconducting transition in resistivity for CsPb 0.3 Bi 3.7 Te 6 can be visibly suppressed under applied magnetic fields. The upper critical field is estimated from the field-dependent transition temperatures as 1.5 T using the Ginzburg−Landau (GL) law 6 [13] and 1.8 T using the Wer-thamer−Helfand−Hohenberg (WHH) theory. [14] This data is much lower than the results as reported for CsBi 4 Te 6 , which shows very high critical field up to 9.7(5), [4] suggesting that the superconducting properties could be quiet different for these two compounds (see Supplementary Information, Fig.…”