Unlocking the thermoelectric potential of the Ca ₁₄ AlSb ₁₁ structure type

Abstract

Yb 14 MnSb 11 and Yb 14 MgSb 11 are among the best p-type high-temperature (>1200 K) thermoelectric materials, yet other compounds of this Ca 14 AlSb 11 structure type have not matched their stability and efficiency. First-principles computations show that the features in the electronic structures that have been identified to lead to high thermoelectric performances are present in Yb 14 ZnSb 11 , which has been presumed to be a poor thermoelectric material. We show that the previously reported low power factor of Yb 14 ZnSb 11 is not intrinsic and is due to the presence of a Yb 9 Zn 4+ x Sb 9 impurity uniquely present in the Zn system. Phase-pure Yb 14 ZnSb 11 synthesized through a route avoiding the impurity formation reveals its exceptional high-temperature thermoelectric properties, reaching a peak zT of 1.2 at 1175 K. Beyond Yb 14 ZnSb 11 , the favorable band structure features for thermoelectric performance are universal among the Ca 14 AlSb 11 structure type, opening the possibility for high-performance thermoelectric materials.

Zintl Phases: From Curiosities to Impactful Materials

“…Therefore, this material was a good starting place in terms of structure to expect a high-temperature, high-efficiency thermoelectric material. Compounds of the general formula Yb 14 MSb 11 (M = Mn, Mg, Zn) − are some of the most efficient high-temperature p-type thermoelectric materials. Finding efficient materials in this temperature range is important due to the greater device efficiencies that result from large thermal gradients.…”

Impact of Lu-Substitution in Yb14–xLuxZnSb11: Thermoelectric Properties and Oxidation Studies

“…16 The error in thermal conductivity is estimated to be ±8%, considering the uncertainties from D, ρ, and C p . 5 Electrical Resistivity. The electrical resistivity of Yb 14−x Lu x ZnSb 11 was measured on a custom-built Hall system at the Jet Propulsion Laboratory (JPL).…”

“…5 The large complex unit cell filled with heavy atoms lends to ultralow thermal conductivities, while degeneracy within the band structure leads to high Seebeck coefficients while maintaining low electrical resistivities all of which are ideal for high thermoelectric performance. 5 The oxidation process of Yb 14 ZnSb 11 as a function of temperature was investigated and compared to the other highperformance analogues, Yb 14 MnSb 11 and Yb 14 MgSb 11 , and showed the most promising passivating oxide shell formation. 8 In addition, Yb 14 ZnSb 11 does not appear to undergo a peritectic with increasing temperature, as observed in the large-scale pellet oxidation of the Mn and Mg analogues.…”

Tuning the Radius Ratio to Enhance Thermoelectric Properties in the Zintl Compounds AM2Sb2 (A = Ba, Sr; M = Zn, Cd)

“…Among the various TE materials, the Zintl phases that have intrinsically complex crystal structures and semiconducting behaviors are considered one of the most promising candidates for this application, and these include the A 14 MPn 11 (A = Ca, Yb; M = Mn, Al; Pn = Sb), , A 11 Pn 10 (A = Ca, Yb; Pn = Ge, Sb, Bi), − A 5 M 2 Pn 6 (A = Ca, Yb; M = Al, In; Pn = Sb, Sn), , and A 2 MPn 2 (A = Ca, Eu, Yb; M = Cd; Pn = Sb) systems. , In particular, worldwide research for the trigonal CaAl 2 Si 2 -type AM 2 Pn 2 (A = Ca, Sr, Ba, Eu, Yb; M = Zn, Cd; Pn = Sb) system has been recently conducted due to its relatively easy dopability and large ZT values. − On the other hand, despite the identical stoichiometry AM 2 Pn 2 , only a few compounds have been reported in the orthorhombic BaCu 2 S 2 -type AM 2 Pn 2 (A = Ba; M = Cu, Zn; Pn = Sb, Te) system for the TE application, such as the Ba 1– x – y Na x Sr y Zn 2 Sb 2 (0 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.1) system, due to its narrow phase-width and limited dopability. − …”

“…Therefore, high electrical conductivity, large Seebeck coefficient, and low thermal conductivity are required to achieve the high ZT value. Among the various TE materials, the Zintl phases that have intrinsically complex crystal structures and semiconducting behaviors are considered one of the most promising candidates for this application, and these include the A 14 MPn 11 (A = Ca, Yb; M = Mn, Al; Pn = Sb), 6,7 A 11 Pn 10 (A = Ca, Yb; Pn = Ge, Sb, Bi), 8−10 A 5 M 2 Pn 6 (A = Ca, Yb; M = Al, In; Pn = Sb, Sn), 11,12 and A 2 MPn 2 (A = Ca, Eu, Yb; M = Cd; Pn = Sb) systems. 13,14 In particular, worldwide research for the trigonal CaAl 2 Si 2 -type AM 2 Pn 2 (A = Ca, Sr, Ba, Eu, Yb; M = Zn, Cd; Pn = Sb) system has been recently conducted due to its relatively easy dopability and large ZT values.…”