Nanostructural and Microstructural Ordering and Thermoelectric Property Tuning in Misfit Layered Sulfide [(LaS) x ] 1.14 NbS 2

P. Jood (1) , M. Ohta (1) , O.I. Lebedev (2) , David Berthebaud (2)

1 AIST - National Institute of Advanced Industrial Science and Technology
2 CRISMAT - Laboratoire de cristallographie et sciences des matériaux

The potential to control the structural ordering at the nanoscale in misfit layered systems can open new paths for achieving high thermoelectric performance in these systems. In the present work, we demonstrate that compositional changes can provide nanoscale tuning in misfit layered (La x S x ) 1.14 NbS 2 (x = 0.90, 0.95, 1.00, 1.05, 1.10), leading to improved thermoelectric properties (investigated over the temperature range of 300 to 950 K). The samples were prepared by CS 2 sulfurization and consolidated using pressure-assisted sintering. It was revealed through transmission electron microscopy analysis that nonstoichiometry promotes long-range ordering of the layers and results in elongated lamella formations. The La deficient x = 0.95 sample was found to contain large strain induced stacking disorder, owing to which the long lamellas rolled up to form tubular structures, whereas the La rich x = 1.05 sample had a much ordered structure and only slight curling of lamella edges was observed. Improved structural ordering and textured grain growth in La rich sample resulted in a ∼30% improved power factor (∼460 μW K -2 m -1 at 950 K) and ZT (∼0.2 at 950 K) in the in-plane direction, compared to the x = 1.00 sample. The origin of very low thermal conductivity (1.1-2.5 W K -1 m -1 at 950 K) in our samples has been identified and discussed in detail. © 2015 American Chemical Society.

Mots clés: Electric power factor; High resolution transmission electron microscopy; Lanthanum alloys; Nanotechnology; Sintering; Thermal conductivity; Thermoelectric equipment; Thermoelectricity; Transmission electron microscopy; Tuning; Compositional changes; Low thermal conductivity; Ordered structures; Pressure assisted sintering; Structural ordering; Thermoelectric performance; Thermoelectric properties; Through transmission; Grain growth; Layers; Grain; Sulfides; Lattices

Domaines: Chimie; Cristallographie; Matériaux; Chimie théorique et/ou physique

P. Jood, M. Ohta, O.I. Lebedev, David Berthebaud. Nanostructural and Microstructural Ordering and Thermoelectric Property Tuning in Misfit Layered Sulfide [(LaS) x ] 1.14 NbS 2. Chemistry of Materials, 2015, 27 (22), pp.7719-7728. ⟨10.1021/acs.chemmater.5b03365⟩. ⟨hal-02184133⟩