The remarkable crystal chemistry of the Ca14AlSb11 structure type, magnetic and thermoelectric properties

Abstract

Yb14MnSb11 is a member of a remarkable structural family of compounds that are classified according to the concept of Zintl. This structure type, of which the prototype is Ca14AlSb11, provides a flexible framework for tuning structure-property relationships and hence the physical and chemical properties of compounds. Compounds within this family show exceptional high temperature thermoelectric performance at temperatures above 300 K and unique magnetic and transport behavior at temperatures below 300 K. This review provides an overview of the structure variants, the magnetic properties, and the thermoelectric properties. Suggestions for directions of future research are provided. One active research area is to systematically explore more complex compositions such as Ca11Sb10, K4Pb9, Na8Si46, Ca14AlSb11 and KBa2InAs3. 3-7 The other direction is to replace the alkaline earth metals with divalent rare earth elements (Sm, Eu and Yb) along with the introduction of transition metals into structures, typically replacing the less electronegative metalloid in the anionic framework. 8-10 Combinations of these two directions led to compounds such as Yb14MnSb11, Pr4MnSb9, Eu10Mn6Sb13, Yb9Zn4+xBi9 and Cs13Nb2In6As10. 11-16 The complexity of compositions can be combined with a small flexibility in electron counting. For example, Yb14MnSb11 and Yb9Zn4+xBi9 do not strictly follow the Zintl-Klemm concept. Yb14MnSb11 has Mn 2+ instead of a group 13 element such as in Ca14AlSb11 and therefore is electron deficient, 17 and Yb9Zn4+xSb9 has interstitial Zn atoms which can be compositionally varied to achieve specific properties. 18 At the same time, the total number of valence electrons within an identical Zintl phase structure type with different elements may also vary slightly but the variance can be quite small and limited for many structure types that can be described by the Zintl concept. Therefore, with the introduction of transition elements, new electronic properties are possible, but complete transfer of electrons and clear counting of valence electrons remains a criterion for describing transition and rare earth metal containing Zintl phase compounds. Binary Zintl phase compounds which have compositions of simple ratios of elements usually adopt the structures of known oxides or halides, in which anions and cations are isolated in the structure with no covalent bonding. 2, 19 Both isolated anions, polyanions or clusters in Zintl phase compounds can provide complex compositions such as those represented by Ca11Sb10 and K4Pb9. 3, 4 Polyanions or clusters are formed to compensate for lack of enough electrons from the electropositive element to satisfy valence to form a simple one atom anion. Sb forms Sb-Sb single bonds in the Ca11Sb10 structure type resulting in Sb2 4and Sb4 2polyanions in the structure. 3 The Zintl electron counting provides the following charge balanced scenario: 11Ca 2+ + 4Sb 3-+ 2Sb2 4-+ Sb4 2-. Two types of clusters exist in K4Pb9 with the same formal oxidation state: a monocapped square antiprism and a tr...

Discovery of multivalley Fermi surface responsible for the high thermoelectric performance in Yb 14 MnSb 11 and Yb 14 MgSb 11

“…S5). This increase in effective mass with temperature and carrier concentration is what previous experimental studies ( 4 , 25 ) have been reported for different compounds of the A 14 MPn 11 structure and is seen in Fig. 5B .…”

“…However, this study could not explain why the Seebeck coefficient of differently doped samples appears to converge near room temperature instead of the expected 0 K for an SPB semiconductor with constant m * ( 24 ). Hu et al ( 4 ) and Kunz Wille et al ( 25 ) have shown the experimental DOS effective mass of A 14 M Pn 11 markedly increases with increasing temperature and suggested a deviation from SPB.…”

Ba2Si3P6: 1D Nonlinear Optical Material with Thermal Barrier Chains

“…Thermal conductivity of 0.56 W m -1 K -1 at 300 K is comparable to that of state-of-the-art thermoelectric materials, such as Yb14MnSb11 (0.7 Wm -1 K -1 at 300 K), Bi0.5Sb1.5Te3 (~0.7 Wm -1 K -1 at 300 K), [010] direction of the SnSe single crystal (0.7 Wm -1 K -1 at 300 K), Zn8Sb7 (0.6 Wm -1 K -1 at 400 K), Ba8Cu14Ge6P26 (0.77 Wm -1 K -1 at 300 K), and LaxBa8-xCu16P30 (~1.1 Wm -1 K -1 at 400 K). [53][54][55][56][57][58] Ba2Si3P6 displays a relatively low absolute value of Seebeck coefficient (−30 µV/K at 300 K) and high resistivity (83 Ωm at 300 K) (Figure 3 middle and bottom). The negative nature of the Seebeck and temperature dependence of resistivity suggest Ba2Si3P6 to be a n-type semiconductor.…”

Synthesis, Crystal and Electronic Structure of Layered AMSb Compounds (A = Rb, Cs; M = Zn, Cd)

“…[7][8][9][10][11] A notable example is the well-known Yb 14 MnSb 11 , which has been identified as an efficient high-temperature p-type leg for thermoelectric generators. [11][12][13] Examining the reported compounds in the ternary alkali metal-antimonide systems, two things become apparent: (i) there is a high number of compounds with 111 stoichiometry that crystallize in extraordinarily common ZrBeSi or PbFCl structure types; and (ii) that a large number of these compounds are found for the lighter alkali metals (Li, Na, or K) while the heavier metals (Rb or Cs) are underrepresented. [14][15] The latter point is not as easily explained.…”