Complex Structural Disorder in Thermoelectric Zintl Phases Eu21M4As18 (M = Mn, Zn)

Document Type

Article

Publication Date

1-1-2025

Abstract

Ternary Zintl arsenides Eu21Mn4As18, Eu21Zn4As18, and quaternary solid solution Eu21Mn4As15.4Sb2.6 have been synthesized and structurally characterized using single-crystal X-ray diffraction. Eu21Mn4As18 and Eu21Mn4As15.4Sb2.6 are reported here for the first time, whereas new structural insights are presented for the previously known Eu21Zn4As18. All title compounds crystallize in the Sr21Mn4Sb18 structure type (space group C2/m) and exhibit pronounced positional disorder affecting both cationic and anionic sites. This includes disorder on Eu atoms and As2 dimers, as well as split M (M = Mn, Zn) sites within the anionic [M8As22]48− clusters. Despite the disorder, the Zintl concept remains applicable to the novel Eu21Mn4As18 phase, and the charge-balanced composition can be expressed as 2 × Eu21Mn4As18 = [Eu2+]42{[Mn8As22]48-}{[As2]4-}3[As3-]8. Electronic structure calculations performed on the disorder-free model of Eu21Zn4As18 predict a bandgap of ≈1.1 eV.

Publication Source (Journal or Book title)

Zeitschrift Fur Anorganische Und Allgemeine Chemie

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