Synthesis and crystal structure of new quaternary sulfides BaLn2FeS5(Ln = La, Ce, Pr, Nd, Sm)

New quaternary sulfides, BaLn2FeS5(Ln = La, Ce, Pr, Nd, Sm) were synthesized by a solid state reaction at 900 or 950°C. These compounds crystallize in the tetragonal structure (space group I4/mcm) with Z = 4. The refinement of the X-ray diffraction data was carried out by the Rietveld method. They have a layered-structure composed of Ln-S layers and Ba-Fe-S layers, which are perpendicular to the c-axis. In these compounds, barium, lanthanide, and iron cations are located in 4a (0, 0, 1/4), 8h (x, x + 1/2, 0), and 4b (0, 1/2, 1/4) sites, respectively. Sulfur anions occupy two different sites, S(1) and S(2) in 4c (0, 0, 0) and 16l (x, x + 1/2, z), respectively. BaSm2FeS5 is a new compound in a series of BaLn2MS5 (M : 3d transition metal).