Identification, structural characterization and transformations of the high-temperature Zn_9−δSb₇ phase in the Zn–Sb system

Abstract

The Zn9-δSb7 phase has been identified via high-temperature powder diffraction studies. Zn9-δSb7 adopts two modifications: an α form stable between 514 °C and 539 °C and a Zn-poorer β form stable from 539 °C till its melting temperature of 581 °C. The Zn9-δSb7 structure was solved from the powder data using the simulated annealing approach. Both modifications adopt the same hexagonal structure (P6/mmm) but with slightly different lattice parameters. The α-to-β transformation is abrupt and first-order in nature. The Zn atoms occupy the tetrahedral holes created by Sb atoms. The ideal Zn9Sb7 composition can be explained by its tendency to adopt a charge balance configuration. Out of 7 Sb atoms, 3 Sb atoms form dimers (Sb(2-) ions) and 4 Sb atoms are isolated (Sb(3-) ions), which require 9 Zn(2+) cations for charge neutrality.

Enhanced thermoelectric performance and high-temperature thermal stability of p-type Ag-doped β-Zn4Sb3

“…In the heating process, the second strongest endothermic peak (x = 0: at 767 K; x = 0.005: at 764 K; x = 0.01: at 769 K) corresponds to the peritectoid reaction from β-Zn 4 Sb 3 to γ-Zn 4 Sb 3 + ζ-Zn 3 Sb 2 phases, the weak peak (x = 0: at 798 K; x = 0.005: at 799 K; x = 0.01: at 804 K) corresponds to the phase transition from γ-Zn 4 Sb 3 to γ'-Zn 4 Sb 3 , and the strongest peak (x = 0 & 0.005: at 839 K; x = 0.01: at 847 K) corresponds to the melting point of γ'-Zn 4 Sb 3 [46]. The two phases (γ-and γ'-Zn 4 Sb 3 ) could be α-and β-Zn 9−δ Sb 7 , respectively [47]. The other two weak peaks at 745 K and 783 K are also present in the sample with x = 0.01, which could be due to the impurity of Ag-Zn compound.…”

The impact of site selectivity and disorder on the thermoelectric properties of Yb21Mn4Sb18 solid solutions: Yb21Mn4−xCdxSb18 and Yb21−yCayMn4Sb18

“…The subset of Zintl phases with complex unit cells gives rise to more phonon modes leading to increased phonon scattering and lower thermal conductivity. Examples of such materials include Yb 14 MnSb 11 , 2,3 Zn-Sb phases, 4,5,6 and Tl 2 Ag 12 Te 7+δ . 7 Other optimization strategies include: electronic structure modification (e.g.…”

Structural evolution in thermoelectric zinc antimonide thin films studied by in situ X-ray scattering techniques

“…Recently, Lo et al (2018) updated the Zn-Sb phase diagram, and White et al (2018) explored the Li-Zn-Sb phase diagram using a solution-phase method. It is now established that there exists a large number of unique Zn-Sb phases within a narrow compositional range (50-60 at% Zn) including ZnSb (Telkes, 1947), Zn 8 Sb 7 (Pomrehn et al, 2011;Wang & Kovnir, 2015), Zn 9 Sb 7 (He et al, 2015), Zn 4 Sb 3 (Caillat et al, 1997) and Zn 3 Sb 2 (Lo et al, 2017;Boströ m & Lidin, 2004). Among these, ZnSb and -Zn 4 Sb 3 are the two well known stable bulk phases at room temperature (RT, $300 K), both exhibiting excellent TE properties (Telkes, 1947;Caillat et al, 1997).…”