New quaternary Zintl phases – Synthesis, crystal and electronic structures of K A2Cd 2Sb 3 ( A = Ca, Sr, Ba, Eu, Yb)

Abstract

The isostructural and isoelectronic Zintl phases K A 2Cd 2Sb 3 ( 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 [Cd 2Sb 3] 5− framework, with K + and A 2+ 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 KEu 2Cd 2Sb 3, confirming divalent Eu are also presented.