Intercalation: Building a Natural Superlattice for Better Thermoelectric Performance in Layered Chalcogenides

• Published in: Journal of electronic materials 2011-05, Vol.40 (5), p.1271-1280
• Main Authors: Wan, Chunlei, Wang, Yifeng, Wang, Ning, Norimatsu, Wataru, Kusunoki, Michiko, Koumoto, Kunihito
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Chromium; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conductivity phenomena in semiconductors and insulators; Electronic transport in condensed matter; Electronics and Microelectronics; Exact sciences and technology; Heat conductivity; Heat transfer; Incommensaturate crystals; Instrumentation; Materials Science; Nature; Optical and Electronic Materials; Phonons; Physics; Rare earth metals; Science; Semi-periodic solids; Softening; Solid State Physics; Structure of solids and liquids; crystallography; Superlattices; Thermal conductivity; Thermoelectric and thermomagnetic effects; Thermoelectricity; Transmission electron microscopy
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-011-1565-5

A natural superlattice with composition (SnS) 1.2 (TiS 2 ) 2 , built by intercalating a SnS layer into the van der Waals gap of layered TiS 2 , has been directly observed by high-resolution transmission electron microscopy (HRTEM). The thermoelectric performance is improved in the direction parallel to the layers because the electron mobility is maintained while simultaneously suppressing phonon transport, which is attributed to softening of the transverse sound velocities due to weakened interlayer bonding. In the direction perpendicular to the layers, the lattice thermal conductivity of (SnS) 1.2 (TiS 2 ) 2 is even lower than the predicted minimum thermal conductivity, which may be caused by phonon localization due to the translational disorder of the SnS layers parallel to the layers. Moreover, we propose a large family of misfit-layer compounds (MX) 1+ x (TX 2 ) n (M = Pb, Bi, Sn, Sb, rare-earth elements; T = Ti, V, Cr, Nb, Ta; X = S, Se; n  = 1, 2, 3) with a natural superlattice structure as possible candidate high-performance thermoelectric materials.