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A new bismuth chalcogenide La0.92Bi1.08S3 in the monoclinic structure was discovered via solid-state reaction. La0.92Bi1.08S3 adopts a novel structure with positional disorder. This material shows a semiconducting behavior with a band gap of ∼1 eV and activation energy for transport of 0.36(1) eV. Band structure calculations confirm the gap is indirect.
The new bismuth chalcogenide La0.92Bi1.08S3 crystallizes in the monoclinic space group C2/m with a = 28.0447(19) Å, b = 4.0722(2) Å, c = 14.7350(9) Å, and β = 118.493(5)°. The structure of La0.92Bi1.08S3 is built of NaCl-type Bi2S5 blocks and BiS4 and LaS5 infinitely long chains, forming a compact three-dimensional framework with parallel tunnels. Optical spectroscopy and resistivity measurements reveal a semiconducting behavior with a band gap of ∼1 eV and activation energy for transport of 0.36(1) eV. Thermopower measurements suggest the majority carriers of La0.92Bi1.08S3 are electrons. Heat capacity measurements indicate no phase transitions from 2 to 300 K. Band structure calculations at the density functional theory level confirm the semiconducting nature and the indirect gap of La0.92Bi1.08S3.
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