It was noted that these new super-ionic conductors crystallized with cubic space groups in which a = 1.09427nm (P4332) or a = 1.05013nm (P4132). These compounds exhibited similar S packings; consisting of S octahedra which shared common edges. In both cases, the M cations (Zr or Sn) were located within the S octahedra (12d sites). The main crystallographic difference between the 2 structures was the Ag packing. In the case of Ag4Zr3S8, the Ag ions were located in 3 different tetrahedral sites; 2 of which were partially occupied. In the case of Ag3.8Sn3S8, the Ag ions were situated only in statistically occupied octahedral sites (12d and 4b); thus giving a rocksalt-type lattice. They were both mixed conductors which exhibited a relatively high ionic conductivity.

O.Amiel, D.C.Frankel, H.Wada: Journal of Solid State Chemistry, 1995, 116[2], 409-21