New quaternary Zintl phases – Synthesis, crystal and electronic structures of KA2Cd2Sb3 (A = Ca, Sr, Ba, Eu, Yb)

The isostructural and isoelectronic Zintl phases KA2Cd2Sb3 (A = Ca, Sr, Ba, Eu, Yb) are the first in the corresponding quaternary systems. They have been synthesized by high-temperature reactions of the respective elements and their structures have been established by single-crystal X-ray diffraction. The orthorhombic structure (space group Pnma, no. 62, Z = 4) is complex and is best described following the Zintl formalism as a channel-like three-dimensional∞3[Cd2Sb3]5− framework, with K+ and A2+ cations filling the space within it. The polyanionic framework is based on corner-shared antimony-tetrahedra, centered by the Cd. Electronic structures calculations using the linear muffin-tin orbital (LMTO) method suggest that the title compounds are electron-precise Zintl phases, evidenced by the small energy gaps at the Fermi level. Magnetic susceptibility data for KEu2Cd2Sb3, confirming divalent Eu are also presented.

Graphical abstractThe new Zintl phases KA2Cd2Sb3 (A = Ca, Sr, Ba, Eu, Yb) are the first antimonides with Cd, and the alkali- and alkaline-earth or rare-earth elements. Their open framework-like crystal structures are based on corner-shared CdSb4-tetrahedra, with distinct and ordered arrangement of cations within the channels.Figure optionsDownload full-size imageDownload as PowerPoint slide