Seven new rare-earth transition-metal oxychalcogenides: Syntheses and characterization of Ln(4)MnOSe(6) (Ln = La, Ce, Nd), Ln(4)FeOSe(6) (Ln = La, Ce, Sm), and La4MnOS6

摘要

The quaternary oxychalcogenides Ln(4)MnOSe(6) (Ln = La, Ce, Nd), Ln(4)FeOSe(6) (Ln = La, Ce, Sm), and La4MnOS6 have been synthesized by the reactions of Ln (Ln = La, Ce, Nd, Sm), M (M = Mn, Fe), Se, and SeO2 at 1173 K for the selenides or by the reaction of La2S3 and MnO at 1173 K for the sulfide. Warning: These reactions frequently end in explosions. These isostructural compounds crystallize with two formula units in space group C-6v(4) - P6(3mc) of the hexagonal system. The cell constants (a, c in &ANGS;) at 153 K are: La4MnOSe6, 9.7596(3), 7.0722(4); La4FeOSe6, 9.7388(4), 7.0512(5); Ce4MnOSe6, 9.6795(4), 7.0235(5); Ce4FCOSe6, 9.6405(6), 6.9888(4); Nd4MnOSe6, 9.5553(5), 6.9516(5); Sm4FeOSe6, 9.4489(5), 6.8784(5); and La4MnOS6, 9.4766(6), 6.8246(6). The structure of these Ln(4)MOQ(6) compounds comprises a three-dimensional framework of interconnected LnOQ(7) bicapped trigonal prisms, MQ(6) octahedra, and the unusual LnOQ(6) tricapped tetrahedra. © 2005 Elsevier Inc. All rights reserved.