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Brown needle-like crystals of CaEr2S4 were isolated as the major product from a reaction of elements and binary sulfides by a two-step flux technique. CaEr2S4 crystallizes in the orthorhombic space group Pnma with a = 12.845(4), b = 3.862(4), c = 13.001(2) , V = 645.0(7) 3, Z = 4, F(000) = 880, μ(MoKα) = 27.794 mm-1, the final R = 0.0528 and wR = 0.0562 for 1070 observed reflections with I > 3σ(I). The CaEr2S4 structure forms a three-dimensional framework that consists of interconnected tetra-octahedral Er4S18 fragments. Ca2+ cations, in a monocapped trigonal prism geometry, are stuffed in two parallel rows into the one-dimensional channels along the b direction. CaEr2S4 is an infrared-transparent semiconductor with a band gap of 1.81 eV. Magnetic susceptibility measurements over 6～300 K indicate a Curie-Weiss paramagnetic behavior for the phase, with an effective magnetic moment of 9.64(1) μB per Er3+ ion.
Brownie-like crystals of CaEr2S4 were isolated as the major product from a reaction of elements and binary sulfides by a two-step flux technique. CaEr2S4 crystallizes in the orthorhombic space group Pnma with a = 12.845 (4), b = 3.862 (4 ), c = 13.001 (2) , V = 645.0 (7) 3, Z = 4, F (000) = 880, μ (MoKα) = 27.794 mm -1, final R = 0.0528 and wR = 0.0562 for 1070 observed reflections with I> 3σ (I). The CaEr2S4 structure forms a three-dimensional framework that consists of interconnected tetra-octahedral Er4S18 fragments. Ca2 + cations, in a monocapped trigonal prism geometry, are stuffed in two parallel rows into the one- Magnetic susceptibility measurements over 6 ~ 300 K indicate a Curie-Weiss paramagnetic behavior for the phase, with an effective magnetic moment of 9.64 (1 ) μB per Er3 + ion.