K7In4As6 and K3InAs2 ‐ Two more Zintl phases showing the rich variety of In‐As polyanion structures

Binary phases of triel (Tr) and pentel (Pn) elements (III‐V semiconductors) represent a unique compound class due to their tunable intrinsic band gap in dependency of the element combination. We report here on two new compounds in the ternary system K−In−As. In K3InAs2 the edge‐sharing tetrahedral InAs4 units are connected via opposed edges of the tetrahedra forming linear [InAs2]3− chains and are thus iso(valence)‐ electronic with SiS2. In K7In4As6, the InAs4 tetrahedra are connected via neighboring edges of the tetrahedra forming zig‐zag chains. These chains are linked in two directions through dimeric [As3In−InAs3] units. Both reported Zintl phases extend the number of structures that possess the same In−As ratio. In K3InAs2 a one‐dimensional polyanion in contrast to known Na3InAs2 comprising a three‐dimensional polyanion structure is found. K7In4As6 forms together with the known phases K2In2As3 and K3In2As3 a series of Zintl phases with the ratio In : As=2 : 3. Even though the three phases differ only slightly in their valence electron concentration (VEC) of the polyanion, the VECs have a strong influence on the structures. Syntheses, crystal structures and the electronic band structures are reported. The compounds are discussed in the context of the Zintl concept.Dedicated to the late Professor Eduard Zintl on the occasion of his 125th birthday