title: Enhanced thermoelectric properties of selenium-deficient layered TiSe(2-x): a charge-density-wave material.
abstract: In the present work, we report on the investigation of low-temperature (300-5 K) thermoelectric properties of hot-pressed TiSe2, a charge-density-wave (CDW) material. We demonstrate that, with increasing hot-pressing temperature, the density of TiSe2 increases and becomes nonstoichiometric owing to the loss of selenium. X-ray diffraction, scanning electron microscopy, and transimission electron microscopy results show that the material consists of a layered microstructure with several defects. Increasing the hot-press temperature in nonstoichiometric TiSe2 leads to a reduction of the resistivity and enhancement of the Seebeck coefficient in concomitent with suppression of CDW. Samples hot-pressed at 850 °C exhibited a minimum thermal conductivity (κ) of 1.5 W/m·K at 300 K that, in turn, resulted in a figure-of-merit (ZT) value of 0.14. This value is higher by 6 orders of magnitude compared to 1.49 × 10(-7) obtained for cold-pressed samples annealed at 850 °C. The enhancement of ZT in hot-pressed samples is attributed to (i) a reduced thermal conductivity owing to enhanced phonon scattering and (ii) improved power factor (α(2)σ).
authors.affiliation: Technical Physics Division, ‡Astrophysical Sciences Division, ∥Solid State Physics Division, and ⊥Chemistry Division, Bhabha Atomic Research Centre , Mumbai 400 085, India.
authors.forename: Ranu
authors.initials: R
authors.lastname: Bhatt
authors.forename: Shovit
authors.initials: S
authors.lastname: Bhattacharya
authors.forename: Ranita
authors.initials: R
authors.lastname: Basu
authors.forename: Sajid
authors.initials: S
authors.lastname: Ahmad
authors.forename: A K
authors.initials: AK
authors.lastname: Chauhan
authors.forename: G S
authors.initials: GS
authors.lastname: Okram
authors.forename: Pramod
authors.initials: P
authors.lastname: Bhatt
authors.forename: Mainak
authors.initials: M
authors.lastname: Roy
authors.forename: M
authors.initials: M
authors.lastname: Navaneethan
authors.forename: Y
authors.initials: Y
authors.lastname: Hayakawa
authors.forename: A K
authors.initials: AK
authors.lastname: Debnath
authors.forename: Ajay
authors.initials: A
authors.lastname: Singh
authors.forename: D K
authors.initials: DK
authors.lastname: Aswal
authors.forename: S K
authors.initials: SK
authors.lastname: Gupta
keywords: interfaces; lattice thermal conductivity; layer microstructure; nanocrystalline materials; thermoelectric material