Zintl phases for thermoelectric applications

Kauzlarich, Susan M.; Devlin, Kasey P.; Perez, Christopher

doi:10.1016/b978-0-12-818535-3.00004-9

Cited by 6 publications

(9 citation statements)

References 79 publications

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“…This complex phase contains eight formula units per unit cell with each formula unit containing 13 Yb +2 cations, 1 Yb +3 cation, 1 [MgSb 4 ] −10 tetrahedron, 1 Sb 3 –7 linear unit, and 4 Sb –3 anions. Yb 14 MgSb 11 and the isostructural Yb 14 MnSb 11 both exhibit excellent high-temperature thermoelectric properties and are under consideration for implementation in radioisotope thermal electric generators for space exploration. − Because of the wide interest in thermoelectric modules for waste heat recovery, an efficient synthetic route to high-purity phases with precise control over stoichiometry will have a significant impact on increasing the progress toward even higher-efficiency materials. − …”

Section: Introductionmentioning

confidence: 99%

2 + 2 = 3: Making Ternary Phases through a Binary Approach

et al. 2022

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Synthetic organic chemists have a large toolbox of named reactions to form structural motifs through a retrosynthetic approach when targeting a complex molecule. On the other hand, a comparatively complex inorganic compound may be made through simple mechanochemical reactions of the elements followed by annealing. For complex phases that involve more than two elements, the simple mechanochemical process can be complex with many competing phases, which can negatively impact desired properties. This point has been made recently with a revelation of improved properties of thermoelectric materials upon the removal of impurities. Compounds of the Yb14AlSb11 structure type represent complex Zintl phases with exceptional high-temperature thermoelectric properties but are difficult to prepare in high purity. In this work, a quenching study was used to elucidate the pathway taken by reactions from the elements to form the complex ternary phase, Yb14AlSb11. Through that study, two Yb–Sb binary phases, Yb11Sb10 and Yb4Sb3, were identified as intermediates in the reaction. These two Yb–Sb binaries were investigated for use as reactive precursors to form Yb14MnSb11 in reactions with MnSb. Through this pseudoretrosynthetic approach, reactions from Yb4Sb3 allowed for the synthesis of high-purity Yb14MnSb11 and Yb14MgSb11 through balanced, stoichiometric reactions. The apparent Yb2O3 (∼1%) impurity found in these products was systematically reduced with x in the series Yb14‑x MnSb11 (x = 0–0.05), suggesting that the main phase is inherently Yb-deficient and showing the high degree of control obtained through this synthetic approach. The stoichiometric sample of Yb14MgSb11 has a peak zT of 1.3 at 1175 K, and the stoichiometric sample of Yb14MnSb11 has a peak zT of 1.2 at 1275 K. This approach to solid-state synthesis provides reproducible products from balanced stoichiometric reactants to form high-purity complex structure types and can be adapted to other difficult ternary systems.

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Section: Introductionmentioning

confidence: 99%

2 + 2 = 3: Making Ternary Phases through a Binary Approach

et al. 2022

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“…Recent interest in high-temperature power applications and thermoelectric generator design has led to an interest in determining the oxidation behavior of a number of important thermoelectric materials, such as Skutterudites, half Heuslers, and SnSe. − While Zintl phases show great promise for thermoelectrics, there are few investigations of their stability in air, especially at the proposed operating temperatures. ,− …”

Section: Introductionmentioning

confidence: 99%

Probing High-Temperature Oxidation of Thermoelectric Phases Yb₁₄MSb₁₁ (M = Mg, Mn, Zn)

Justl

Kauzlarich

2022

ACS Appl. Mater. Interfaces

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Yb14 MSb11 (M = Mg, Mn, Zn) are p-type Zintl phases with high thermoelectric efficiencies at 1000 °C and melting points above 1200 °C under vacuum and/or inert atmosphere. In a thermoelectric generator, even within a vacuum jacket, small amounts of oxygen may be present, and therefore, elucidating chemical reactions in the presence of air or oxygen provides a framework for engineering design. The oxidation of Yb14 MSb11 was investigated from room temperature to 1000 °C in dry air with thermogravimetric/differential scanning calorimetry (TG/DSC) on small pellets and visually after heat treatment to 1000 °C under ambient conditions on large pellets. Scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and powder X-ray diffraction provide identification of the oxidation products. In the presence of dry air, Yb14 MSb11 initially oxidizes initially slowly at room temperature with a sweeping exotherm and weight gain with rapid oxidation at 400 °C, after which the exotherm signal plateaus at about 600 °C, with M = Zn showing the smallest overall exothermic curve. All samples showed a paired endo-/exotherm at 785–803 °C, consistent with the melting/solidification of YbSb2, which in the case of M = Mg, Mn extrudes from the sample. The various sections of the pelletsouter layer, inner layer, and core are analyzed, and oxidation reactions are proposed. After cycling to 1000 °C, the outer layer is composed of Yb2O3 with small amounts of the corresponding metal oxides. The inner layer shows delamination by inward diffusion of oxygen and outward diffusion of Sb or Sb oxide-containing phases, and the core shows Yb14 MSb11. Yb14ZnSb11 shows the best resistance to oxidation and may provide a promising material for further passivation optimization.

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“…Band structure of Yb 14 ZnSb 11 The champion high-temperature p-type thermoelectric materials Yb 14 MnSb 11 and Yb 14 MgSb 11 (zT = 1.33 and 1.28, respectively) form in the Ca 14 AlSb 11 structure type, which can accommodate a number of different elements (8). Compounds of this structure type fall under the description of Zintl phases where simple electron counting rules can be used to rationalize the bonding and are considered semiconductors (9)(10)(11)(12). Figure 1 shows the crystal structure of Ca 14 AlSb 11 that contains eight formula units, each of which can be described as consisting of 14 Ca 2+ cations, a [AlSb 4 ] 9− tetrahedron, a Sb 3 7− linear unit, and four Sb −3 anions.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2022

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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.

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Zintl phases for thermoelectric applications

Cited by 6 publications

References 79 publications

2 + 2 = 3: Making Ternary Phases through a Binary Approach

2 + 2 = 3: Making Ternary Phases through a Binary Approach

Probing High-Temperature Oxidation of Thermoelectric Phases Yb₁₄MSb₁₁ (M = Mg, Mn, Zn)

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

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Zintl phases for thermoelectric applications

Cited by 6 publications

References 79 publications

2 + 2 = 3: Making Ternary Phases through a Binary Approach

2 + 2 = 3: Making Ternary Phases through a Binary Approach

Probing High-Temperature Oxidation of Thermoelectric Phases Yb14MSb11 (M = Mg, Mn, Zn)

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

Contact Info

Product

Resources

About

Probing High-Temperature Oxidation of Thermoelectric Phases Yb₁₄MSb₁₁ (M = Mg, Mn, Zn)

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