p-Type Double Doping and the Diamond-like Morphology Shift of the Zintl Phase Thermoelectric Materials: The Ca11–xAxSb10–yGez (A = Na, Li; 0.06(3) ≤ x ≤ 0.17(5), 0.19(1) ≤ y ≤ 0.55(1), 0.13(1) ≤ z ≤ 0.22(1)) System
| Autor: | Hayeon Sa, Dohyun Moon, Tae-Soo You, Hongil Jo, Min Kim, Kang Min Ok, Junsu Lee |
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| Rok vydání: | 2021 |
| Předmět: |
Dopant
010405 organic chemistry Chemistry Crystal structure 010402 general chemistry 01 natural sciences 0104 chemical sciences Inorganic Chemistry Electronegativity Crystal Crystallography Tetragonal crystal system Zintl phase Seebeck coefficient Physical and Theoretical Chemistry Ternary operation |
| Zdroj: | Inorganic Chemistry. 60:10124-10136 |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/acs.inorgchem.0c03705 |
| Popis: | Five ternary and quaternary Zintl phases in the solid-solution Ca11-xAxSb10-yGez (A = Na, Li; 0.06(3) ≤ x ≤ 0.17(5), 0.19(1) ≤ y ≤ 0.55(1), 0.13(1) ≤ z ≤ 0.22(1)) system have been successfully synthesized by both of the arc-melting and the molten Pb metal-flux reactions. The crystal structure of these title compounds was characterized by powder and single-crystal X-ray diffractions analyses, and all title compounds crystallized in the Ho11Ge10-type phase in the tetragonal space group I4/mmm (Z = 4, Pearson code tI84). The complex crystal structure can be described as an assembly of 1) three kinds of cationic polyhedra centered by three different Sb and 2) the cage-shaped anionic frameworks built through the connection of two types of Sb. The newly substituted p-type double dopants of the cationic (Na and Li) and anionic (Ge) elements displayed particular site preferences, which were successfully explained by either the size-factor criterion based on the atomic size or the electronic-factor criterion based on the electronegativity of an element. Quite interestingly, as the reaction conditions were changed, the morphology shift of single crystals in Ca10.94(3)Na0.06Sb9.58(1)Ge0.21 occurred from a cubic-shaped to a hummocky-type, to a hopper-type, and eventually to an octahedral-shaped crystal, just like the Yakutian kimberlite diamonds. Moreover, we firmly believe that the inclusion of the p-type Ge dopant for Sb was crucial to trigger this type of morphology shift and complete the octahedral-shaped morphology in the overall crystal-growth mechanism. The theoretical calculations using a DFT method rationalized the observed site preference of Na and the electronic effect of the p-type Ge dopants. The Seebeck coefficient measurements for Ca10.88(4)Li0.12Sb9.45(1)Ge0.21 indicated that some portions of electron charge carriers were effectively eliminated by the p-type double dopants using Li and Ge. |
| Databáze: | OpenAIRE |
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