From NaSc 3 Ga 2 Q 8 (Q = S, Se) to KGa 2 In 3 S 8 : substitution of Sc 3+ with In 3+ to achieve doubled birefringence

Three new chalcogenides, AM 5 Q 8 (A = Na, K; M = Sc, Ga and In; Q = S, Se), with a new structure feature 3 D channel-like frameworks. Substitution of Sc with In enhances the anisotropy of microscopic polarizability and achieves birefringence doubling.