From the Ternary Phase Ca₁₄Zn_1+δSb₁₁ (δ ≈ 0.4) to the Quaternary Solid Solutions Ca_14–xRE_xZnSb₁₁ (RE = La–Nd, Sm, Gd, x ≈ 0.9). A Tale of Electron Doping via Rare-Earth Metal Substitutions and the Concomitant Structural Transformations

Abstract

The ternary compound Ca 14 Zn 1.37(1) Sb 11 and its six rare-earth metal substituted derivatives Ca 14−x RE x ZnSb 11 (RE = La−Nd, Sm, Gd; x ≈ 0.90 ± 0.06) have been synthesized and structurally characterized by singlecrystal X-ray diffraction methods. All compounds formally crystallize in the tetragonal Ca 14 AlSb 11 structure type (space group I4 1 /acd, No. 142, Z = 8). The crystal structure of Ca 14 Zn 1.37(1) Sb 11 subtly differs from the structure of the remaining six, as well as from the structure of the archetype, due to the presence of a partially occupied interstitial Zn position. The extra zinc atom is needed in this structure to alleviate the unfavorable number of valence electrons in the imaginary Ca 14 ZnSb 11 . Electron doping, via substitution of RE 3+ ions on Ca 2+ sites, is shown as an alternative route to achieve electron balance in these Zn-based analogs of the Ca 14 AlSb 11 structure, which does not require the incorporation of interstitial atoms. Electrical resistivity measurements done on single-crystalline samples are in agreement with the notion that Ca 14−x RE x ZnSb 11 moieties behave as either bad metals or heavily doped semiconductors. Magnetization measurements show Curie−Weiss paramagnetic behavior related to the local-moment magnetism of the RE 3+ ions.

Synthesis, Structural Characterization and Chemical Bonding of Sr7Li6Sn12and its Quaternary Derivatives with Eu and Alkaline Earth Metal (Mg, Ca, Ba) Substitutions. A Tale of Seven Li‐Containing Stannides and Two Complex Crystal Structures

“…–6 eV, the Sn 2 ‐dimers are in the antibonding states. Similar characteristics of DOS for the homoatomic bonds of many main group element have been reported in previous studies , , …”

Chemical Flexibility of Mg in Pnictide Materials: Structure and Properties Diversity

“…The tetrahedral anion [BSb 4 ] z − ( z depends on the divalent or trivalent nature of the B atoms) is structurally flexible in 14–1–11 structures. When Mg atoms occupy the B atom site, this results in Mg–Sb interatomic distances of 2.806 Å, which is slightly longer than the corresponding B–Sb distances in other 14–1–11 compounds: Zn–Sb (2.731 Å), Mn–Sb (2.742 Å), and Al–Sb (2.781 Å). − , Chemical bonding analysis using the electron localization function demonstrated the covalent nature of interactions between Mg and Sb in Ca 14 MgSb 11 . Full replacement of the MnSb 4 tetrahedra with MgSb 4 ones pointed toward a covalent metal-like role of Mg.…”

“…For the Zintl family X 14 BPn 11 (X = Ca, Sr, Ba, Eu, Yb; B = Mn, Nb, Zn, Cd, Al, Ga, In; Pn = P, As, Sb, Bi) more than 30 derivatives have been reported and exhibited interesting physical properties, such as the thermoelectric effect and magnetoresistance. − ,, These phases, abbreviated as 14–1–11, opened a new chapter for Zintl phases because of their extraordinary thermoelectric performance. The general trend of X 14 BPn 11 is as follows: X site occupied by a divalent alkaline-earth or rare-earth metal; B site occupied by a transition or post-transition metal or main group element of group 13; and Pn site being a pnictogen.…”

New n-Type Zintl Phases for Thermoelectrics: Discovery, Structural Characterization, and Band Engineering of the Compounds A2CdP2 (A = Sr, Ba, Eu)

“…The highly reducing nature of the reaction mixture was shown to, in previous experiments, react at high temperatures with the standard alumna crucibles causing undesirable cracking. 27,28 Single crystals of Eu 2 CdP 2 and Sr 2 CdP 2 were obtained by heating the reactants from 373 K to 1173 K at a rate of 200 K/hr. The peak temperature was held for 24 hrs and then slowly cooled to 823 K at a rate of 3 K/hr.…”