The cubic structure of Li 3 As stabilized by substitution - Li 8 TtAs 4 (Tt = Si, Ge) and Li 14 TtAs 6 (Tt = Si, Ge, Sn) and their lithium ion conductivity.

The new lithium arsenidotetrelates Li 8 SiAs 4 , Li 8 GeAs 4 , Li 14 SiAs 6 , Li 14 GeAs 6 and Li 14 SnAs 6 were synthesized via ball milling and structurally characterized by Rietveld analysis of X-ray powder diffraction data. The aliovalent substitution of lithium in hexagonal Li 3 As by introducing a tetravalent tetrel cation stabilizes cubic structures for Li 8 TtAs 4 (Tt = Si, Ge) in the space group Pa 3̄ and for the lithium richer compound Li 14 TtAs 6 (Tt = Si, Ge, Sn) in the higher symmetrical space group Fm 3̄ m (no. 225). Thermal properties of the arsenidotetrelates were investigated via high temperature powder diffraction and differential thermal analysis revealing a decomposition process of the lithium richer arsenidotetrelate (Li 14 TtAs 6 → Li 8 TtAs 4 + 2Li 3 As) into the lithium poorer arsenidotetrelates and lithium arsenide at moderate temperatures. Impedance spectroscopy shows moderate to good lithium ion conductivity for the lithium arsenidotetrelates.