Synthesis and characterization of a series of quaternary chalcogenides BaLnMQ(3) (Ln = rare earth, M = coinage metal, Q = Se or Te)

The compounds BaGdAuSe3, BaLaCuTe3, BaYCuTe3, BaYAgTe3, BaLaAgTe3, BaYbCuTe 3, BaGdAgTe3, BaNd CuTe3, and BaPrCuTe3, were prepared by the reaction in a BaBr2/KBr flux at 850 degrees C of a rare earth, a coinage-group metal, a chalcogen, and BaSe or BaTe, The unit cells of all of the compounds and the crystal structures of the first four compounds were determined by single-c rystal X-ray diffraction methods. With the exception of BaLaCuTe3,, which c rystallizes with four formula units in the orthorhombic space group Pnma, a ll of these compounds crystallize with four formula units in the orthorhomb ic space group Cmcm. BaLaCuTe3,, isostructural with beta-BaLaCuSe3, and Eu2 CuS3 (i.e., EU2+EU3+CU+(S2-)(3)), and BaCdAuSe3, BaYCuTe3, and BaYAgTe3, is ostructural with KZrCuS3, crystallize in a layered structure in which there are (2)(infinity)[LnMQ(3)(2-)] layers separated by Ba2+ ions, Ln atoms are coordinated by six Q atoms at the corners of a distorted octahedron, and M atoms are coordinated by four Q atoms at the corners of a tetrahedron. The layers are formed by the connection of edge-sharing octahedral chains and corner-sharing tetrahedral chains, Ba atoms are coordinated by seven Q atom s in BaLaCuTe3, and by eight Q atoms in BaGdAuSe3,. BaYCuTe3, and BaYAgTe3, . BaNdAgTe3, show's temperature-dependent; paramagnetism. Its magnetic susc eptibility follow's the Curie-Weiss law. The effective magnetic moment of 3 .4(3)mu(B) is in agreement with the theoretical value of 3.6 mu(B) for Nd3. (C) 1999 Academic Press.