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Syntheses, Crystal and Electronic Structures, and Physical Properties of Two Quaternary Chalcogenides: La4FeSb2Q10 (Q = S, Se)

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posted on 21.12.2009, 00:00 by Hua-Jun Zhao, Long-Hua Li, Li-Ming Wu, Ling Chen
Two new quaternary chalcogenides, La4FeSb2S10 and La4FeSb2Se10, have been synthesized from the stoichiometric mixture of elements by solid-state reactions at 1100 °C. The compounds crystallize in the orthorhombic space group Pbcm with a = 15.066(4) Å, b = 7.590(2) Å, c = 13.341(4) Å, and Z = 4 and a = 15.596(5) Å, b = 7.869(2) Å, c = 13.960(4) Å, and Z = 4, respectively. These structures represent an unique three-dimensional network, in which SbQ3 trigonal pyramids (Sb−S < 2.60 Å, Sb−Se < 2.80 Å) are connected via a relatively weak Sb−Q bond (Sb−S ≈ 2.90 Å, Sb−Se ≈ 3.00 Å) in a novel teeter-totter (SbQ4)n chain motif. The theoretical studies confirm the Sb−Q bonding interactions within such teeter-totter chains. Their optical band gaps are measured to be 1.00 and 0.85 eV. At room temperature, their electrical conductivities are about 10−4 S/cm. Both compounds display antiferromagnetic interactions between Fe centers, and their effective magnetic moments are 5.25 and 6.17 μB, respectively.