Effect of Te addition and texturing on the thermoelectric properties of TiS2 ceramics

Abstract

Dense ceramics with a nominal composition of TexTiS2 were prepared utilizing a liquid-assisted shear exfoliation (LASE) process and spark plasma sintering for improved thermoelectric performance by manipulating transport properties and texturing. Microstructural investigations showed significantly improved (00l)-texturing and refined grains independent of Te addition due to the LASE process. In addition, Te addition caused a gradual reduction of carrier concentration along with enhanced carrier mobility and unaffected density-of-states effective mass in spite of a slight decrease of bandgap, leading to an optimal power factor of PF ∼ 16 μW cm−1 K−2 obtained with x = 0.01, which is about 1.6 times larger that of the pristine sample. Unexpectedly, lattice thermal conductivity increased with increasing x, which can be correlated with the strengthened inter-layer forces despite the alloying effect, as evidenced by the increased longitudinal and transverse phonon velocities. This anomaly outlined an important guidance for TiS2 like layered thermoelectric that a high carrier concentration would be beneficial to achieve a low lattice thermal conductivity.