STRUCTURE, ELECTRICAL TRANSPORT, AND MAGNETIC-PROPERTIES OF THE MISFIT LAYER COMPOUND (PBS)1.13TAS2

(PbS)1.13TaS2, formerly designated "PbTaS3," has been found by single-crystal X-ray diffraction to be a misfit layer compound characterized by two face-centered orthorhombic unit cells each with space group Fm2m. One belongs to the PbS part of the structure (a = 5.825Å, b = 5.779Å, c = 23.96Å, Z = 8), the other belongs to the TaS2 part of the structure (a′ = 3.304Å, b′ = 5.779Å, c′ = 23.96Å, Z = 4). The corresponding axes are parallel; the ratio of the lengths of the misfit a axes, a a′ is irrational, but close to 7 4. The compound is built of alternately double layers of PbS with distorted NaCl-type structure and TaS2 sandwiches, with Ta in distorted trigonal prisms of sulfur. Along the c axes of length 23.96 Å, four units are stacked; units of the same type but ( 1 2)c apart are displaced with respect to each other over ( 1 2)b. The symmetry of the complete structure is analyzed in terms of a four-dimensional superspace group. The electrical transport and magnetic properties are related to those of 2HTaS2. The conduction is metallic and strongly anisotropic, the in-plane resistivity being about 105 smaller than the resistivity along the c axis. The Hall coefficient, with positive sign, corresponds with an electron donation from PbS to TaS2. The Seebeck coefficient is negative like that in other intercalates of 2HTaS2. The compound is Pauli-paramagnetic. © 1990.