Li₃TrAs₂ (Tr=Al, Ga, In) – Derivatives of the antifluorite type structure, conductivities and electronic structures

Abstract

Dedicated to Prof. Wolfgang Schnick on the occasion of his 65 th birthday. Li 3 AlAs 2 , Li 3 GaAs 2 and Li 3 InAs 2 were obtained from the elements via high temperature synthesis. Li 3 AlAs 2 and Li 3 GaAs 2 crystallize in a distorted 2 • 2 • 1 superstructure of the antifluorite structure type. The orthorhombic crystal structure is isotypic to Li 3 AlP 2 and Li 3 GaP 2 , space group Cmce (No. 64) showing layers of condensed TrAs 4 -tetrahedra (Tr = Al, Ga). Li 3 InAs 2 crystallizes isotypic to Li 3 InP 2 in a distorted 2 • 2 • 4 antifluorite type super-structure. The crystal structure is tetragonal, space group I4 1 / acd (No. 142), showing a 3D-network of In 4 As 10 -supertetrahedra. Structural characterization by powder X-ray diffraction, thermal analysis, conductivity measurements and band structure calculations show ion conductivity for Li 3 InAs 2 and electronic charge transport for Li 3 AlAs 2 and Li 3 GaAs 2 .

The cubic structure of Li3As stabilized by substitution – Li8TtAs4 (Tt = Si, Ge) and Li14TtAs6 (Tt = Si, Ge, Sn) and their lithium ion conductivity

“…Recently our group presented the lithium arsenidotrielates Li 3 AlAs 2 , Li 3 GaAs 2 and Li 3 InAs 2 showing, that we can exchange phosphorus by arsenic not just in binary, but also in ternary compounds. 13 With the new compounds Li 8 TtAs 4 (Tt = Si, Ge) and Li 14 TtAs 6 (Tt = Si, Ge, Sn) discussed here we expand the family of arsenidotetrelates to higher lithium content showing similar structural features and properties like the phosphidebased compounds. These ternary phases can be understood as an aliovalent substitution of four lithium cations in Li 3 As by one tetrel cation (Li 12 As 4 → Li 8 Tt 4+ As 4 , Tt = Si, Ge; Li 18 As 6 → Li 14 Tt 4+ As 6 , Tt = Si, Ge, Sn).…”