Syntheses and Structures of the New Quaternary Compounds Ba4Nd2Cd3Se10 and Ba4Ln2Cd3S10 (Ln=Sm, Gd, Tb)

The compounds Ba4Nd2Cd3Se10 and Ba4Ln2Cd3S10 (Ln=Sm, Gd, Tb) have been synthesized at 1173 K with the use of a BaBr2/KBr eutectic flux. These isostructural compounds crystallize as racemic twins in space group Cmc21 of the orthorhombic system in cells of (Ln, Q, a, b, c (?), T (K)): Nd, Se, 4.3340(9), 18.667(4), 27.376(6), 115; Sm, S, 4.1907(8), 17.931(4), 26.594(5), 153; Gd, S, 4.1726(4), 17.928(2), 26.638(3), 153; Tb, S, 4.1643(8), 17.916(4), 26.581(5), 153. The corresponding R1 indices for the refined structures are 0.053, 0.029, 0.032, and 0.030. The structure comprises [Ln2Cd3Q10]4layers interconnected by Ba atoms. There are LnQ6 octahedra and severely distorted CdQ4 tetrahedra in the structure. Ba4Tb2Cd3S10, which is paramagnetic, obeys the Curie–Weiss law and has an effective magnetic moment of 9.94(3) MUB. A band gap of 3.0 eV for this material was deduced from its diffuse reflectance spectrum.