Two new phases in the ternary RE-Ga-S systems with the unique interlinkage of GaS building units: synthesis, structure, and properties.

Two novel ternary rare-earth chalcogenides, YbGaS and LuGaS, have been prepared by solid-state reactions of an elemental mixture at high temperatures. Their structures were determined on the basis of single-crystal X-ray diffraction. YbGaS crystallizes in the monoclinic space group C2/m (no.12) [a = 23.557(2) Å, b = 3.7664(4) Å, c = 12.466(1) Å, β = 90.915(9)°, V = 1105.9(2) Å and Z = 2], whereas LuGaS crystallizes in the triclinic space group P1[combining macron] (no.2) [a = 7.735(3) Å, b = 10.033(4) Å, c = 10.120(4) Å, α = 106.296(4)°, β = 100.178(5)°, γ = 101.946(3)°, V = 714.1(5) Å and Z = 2]. Both the structures feature complicated three dimensional frameworks with the unique interlinkages of GaS as basic building units. Significantly, photo-electrochemical measurements indicated that title compounds were photoresponsive under visible-light illumination. Furthermore, the UV-visible-near IR diffuse reflectance spectra, thermal stabilities, electronic structures, physical properties as well as a structure change trend of the ternary rare-earth/gallium/sulfur compounds have been evaluated.