Thermoelectric properties of a series of polycrystalline Mo(Se_1−xTe_x)₂

Abstract

Transition metal dichalcogenides have being actively studied on the account of their large density-of-state effective mass and low lattice thermal conductivity. Herein, thermoelectric and electrical transport properties of MoSe 2 -MoTe 2 system are investigated. A series of Mo(Se 1−x Te x ) 2 (x = 0, .25, .5, .75, and 1) polycrystalline samples was synthesized by conventional solid-state reaction. Single hexagonal phase was identified for each sample without secondary phase, confirming the formation of complete solid solutions between MoSe 2 and MoTe 2 .The electrical conductivity and magnitude of the Seebeck coefficient increased simultaneously with increasing Te content x at high temperatures, with the power factor following the same trend. As results, the MoTe 2 sample exhibited the maximum power factor of .014 mW/(m K 2 ) at 823 K. The lattice thermal conductivities of the alloyed samples (x = .25, .5, and .75) significantly decreased compared to MoSe 2 and MoTe 2 owing to point defect phonon scattering via anion substitution, which is verified by the Debye-Callaway model. A maximum zT of .0044 was obtained for MoTe 2 sample at 773 K; however, the calculated quality factor B values of the samples with x = .75 and 1 at 773 K were almost identical, suggesting that a further enhancement of zT can be achieved by optimizing an n H of the Mo(Se 0.25 Te 0.75 ) 2 sample. K E Y W O R D Schalcogenides, thermal conductivity, thermoelectric properties 1 where S, σ, κ tot , and T are the Seebeck coefficient, electrical conductivity, total thermal conductivity, and absolute temperature, respectively, and generally, the κ tot is divided 3170