Synthesis, structural and spectroscopic properties of orthorhombic compounds BaLnCuS(3) (Ln = Pr, Sm)

Nikita O.Azarapin Aleksandr S.Aleksandrovsky Victor V.Atuchin Tatyana A.Gavrilova Aleksandr S.Krylov Maxim S.Molokeev ShaibalMukher Aleksandr S.Oreshonkov Oleg V.Andreev JOURNAL OF ALLOYS AND COMPOUNDS

Ternary sulfides BaPrCuS3 and BaSmCuS3 are first synthesized by the sulphidation reaction of a mixture of related oxides and metal Cu in a flow of (CS2, H2S) at 1170 K. The crystal structures of BaPrCuS3 and BaSmCuS3 are obtained by Rietveld method. BaPrCuS3 crystallizes in space group Pnma with unit cell parameters a = 10.56074(6), b = 4.11305(2) and c = 13.42845(7) angstrom, V = 583.289 (5) angstrom(3), Z = 2 (structure type Eu2CuS3). BaSmCuS3 crystallizes in space group Cmcm with unit cell parameters a = 4.07269(4), b = 13.4499(1) and c = 10.3704(1) angstrom, V = 568.06 (1) angstrom(3), Z = 2 (structure type KZrCuS3). The structural model is proposed for the Cmcm -> Pnma transition in ABCX(3) (X = S, Se) compounds for the sequence Sm-Pm-Nd-Pr. The dimensionless tolerance factor t = IR(A) x IR(C)/IR(B)(2) is suggested to control the boundary between the Cmcm and Pnma structures. The micromorphological, thermal and spectroscopic properties are evaluated for BaPrCuS3. The compound melts incongruently at T-melt = 1580.9 K. In BaPrCuS3, the band gap is estimated to be 2.1 eV. The vibrational parameters of BaPrCuS3 and BaSmCuS3 are comparatively observed by Raman spectroscopy. (c) 2019 Published by Elsevier B.V.