Un compose a structure feuilietee (LaO)4Ag1,5Ga1,5S5

The compound (LaO)₄Ag_{1 · 5}Ga_{1 · 5}S₅ belongs to the quasi-binary La₂O₂SAgGaS₂ system. It undergoes a peritectic decomposition at 1040°C and a order-disorder transition at 750°C. The high temperature variety is tetragonal, with $\text{a}{}_0\text{= 4.18}\text{A}\text{?}$; $\text{c}{}_0\text{= 18.74}\text{A}\text{?}$; Z = 1; space group 1422; it has the same structural type as (CeO)₄Ga₂S₅. The low temperature variety is an orthorhombic superstructure of the preceding one. with a = 17.58 (3 a₀√2); b = 5.90 (a₀√2) and $\text{c}\text{= 18.66}\text{A}\text{?}$ (c₀). The electrical conductivity is mainly of ionic nature. The e.m.f. measurements of a cell Ag/(LaO)₄Ag_{1 · 5}Ga_{1 · 5}S₅/S.C./Pt support this conclusion.