Realization of an Ultrahigh Power Factor and Enhanced Thermoelectric Performance in TiS2 via Microstructural Texture Engineering.

Abstract

Layered 1T-type TiS2 powders were pretreated by an ethanol-based shear pulverization process, which showed outstanding effectiveness in reducing the average grain size and narrowing the size distribution while maintaining high crystallinity and plate-shaped morphology. The resulting bulk ceramics densified by spark plasma sintering possessed a highly (00l)-oriented texture and pronounced anisotropy. They showed a noticeably increased σ and an unaffected S in the in-plane direction due to the increased carrier mobility μ and the constant carrier concentration n, which resulted in a significant enhancement of the in-plane power factor, optimally to an unprecedented high level of 1.6-1.8 mW m-1 K-2 in a range of 323-673 K. Meanwhile, the lattice thermal conductivity was reduced by approximately 20% due to the intensified grain boundary phonon scattering that overwhelmed the effect due to texturing. These effects not only demonstrated the powder shear pulverization pretreatment as a facial and reliable route toward a high-textured TiS2 but also enabled a remarkable increase of ZT record for TiS2-based thermoelectrics (TEs) to approximately 0.7 at 673 K, indicating clearly the significant effect of texture engineering on TE performance.