The crystal structure of Er2.34La0.66Ge1.28S7 and the LaxRyGe3S12 phases (R – Tb, Dy, Ho and Er)

Highlights: • Isothermal section of the Er₂S₃–La₂S₃–GeS₂ system was investigated. • The crystal structure of La_4–4xR_4xGe₃S₁₂ alloys (x = 0–0.75, R – Tb, Dy, Ho and Er) was investigated. • The crystal structure of a new quaternary compound Er_2.34La_0.66Ge_1.28S₇ was determined. Isothermal section of the Er₂S₃–La₂S₃–GeS₂ system at 770 K was investigated. The phase boundaries of the solid solution La_4–4xR_4xGe₃S₁₂ (x = 0–0.75, R – Tb, Dy, Ho and Er) were determined, and their structure was investigated by single crystal and powder X-ray diffraction. The existence of new quaternary compound Er_2.34La_0.66Ge_1.28S₇ was established and its crystal structure was determined by X-ray single crystal diffraction (space group 6₃, Pearson symbol h24–1.44, a = 0.96934(3) nm, c = 0.58680(2) nm, R₁ = 0.0220).