ZrSe₃-Type Variant of TiS₃: Structure and Thermoelectric Properties

A dense TiS3 sample has been processed by Spark Plasma Sintering. The structural analysis, obtained by coupling powder X-ray diffraction and transmission electron microscopy (TEM), shows that the A-variant of the ZrSe3-type structure is stabilized for the first time. Defects along the main atomic layer stacking directions are evidenced by high-resolution TEM, which explain the peculiar X-ray powder diffraction patterns, with strongly anisotropic microstrains. The presence of these structural defects might explain the existence of a metal-to-insulator transition with a charge localization below TMI ≈ 325 K. Large absolute values of the Seebeck coefficient, in the range −700 ≤ S ≤ −600 μV·K–1, are observed for 100 ≤ T ≤ 600 K, together with a low thermal conductivity, κ = 2 W·K–1·m–1 at 600 K. The T–1 dependence of the lattice part of κ indicates its phononic character. As the charge carrier concentration measured by Hall effect is too low, n = 1.24 × 1018 cm–3, extra doping would be necessary to decrease its too high electrical resistivity (ρ300K ∼ 1.4 Ω·cm) for thermoelectric applications.