Synthesis of the NaGa(S1-xSex)2 solid solution from mechanically activated precursors

Abstract

NaGaS₂ and NaGaSe₂ are two recently discovered compounds that crystallize in the same structure type. In this work, NaGa(S_1-xSe_x)₂ (x = 0.5, 0.75 and 1) are prepared by an alternative synthesis route, mechanochemistry followed by heat treatment. Na₂S, Na₂Se, Ga₂S₃ and Ga₂Se₃ are milled in stoichiometric proportions. Differential scanning calorimetry, X-ray diffraction and solid-state nuclear magnetic resonance ( ²³Na and ⁷¹Ga) show that the compounds after milling are composed of crystalline NaGa(S_1-xSe_x)₂ with an amorphous part. Annealing promotes the formation of crystalline NaGa(S_1-xSe_x)₂. A linear variation in the lattice parameters is observed, indicating that a solid solution is formed and that Se substitutes for S.