Rapid Phase Screening via Hydride Route: A Discovery of K8–xZn18+3xSb16

A new antimonide K8–xZn18+3xSb16 was synthesized using reactive potassium hydride KH as a precursor. Owing to intimate mixing of starting materials, the hydride route allows rapid phase “screening” of ternary systems and is particularly suitable for the search of new antimonides. The crystal structure of K8–xZn18+3xSb16 (x = 1.12(8); P42/nmc (no. 137), a = 12.3042(5) Å, c = 7.3031(3) Å, V = 1105.6(1) Å3, R1 = 0.029) has a [Zn18Sb16] framework with large channels alternately filled by K cations and Zn3 triangular units. The Zn3 triangles break the channels into finite cages by forming covalent bonds to the framework, preventing K migration along the channel. This structural feature is responsible for its stability in air, uncommon for this class of compounds, as well as for its low thermal conductivity. Transport property measurement and computational analysis of the electronic structure indicate that the title compound is a semimetal with properties highly dependent on the precise composition, i.e., the K/Zn3 ratio in the channels. The hydride preparative route provides accurate control over the composition of the target phase, thereby facilitating transport properties tuning. This synthetic method will allow for the synthesis of novel alkali metal antimonides as well as for the development of functional materials via precise compositional control.