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

摘要

Two new quaternary chalcogenides, La4FeSb2S10 and La4FeSb2Se10, have been synthesized from the stoichiometric mixture of elements by solid-state reactions at 1100 . The compounds crystallize in the orthorhombic space group Pbcm with a = 15.066(4) A° , b = 7.590(2) A° , c = 13.341(4) A° , and Z = 4 and a = 15.596(5) A° , b = 7.869(2) A° , c = 13.960(4) A° , and Z = 4, respectively. These structures represent an unique three-dimensional network, in which SbQ3 trigonal pyramids (Sb-S < 2.60A° , Sb-Se < 2.80A° ) are connected via a relatively weak Sb-Q bond (Sb-S≈ 2.90 A° , Sb-Se ≈ 3.00 A° ) 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 uB, respectively.