Sk S, Shahi N, Pandey SK. Experimental and computational approaches to study the high temperature thermoelectric properties of novel topological semimetal CoSi.
J Phys Condens Matter 2022;
34:265901. [PMID:
35390770 DOI:
10.1088/1361-648x/ac655a]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 04/07/2022] [Indexed: 06/14/2023]
Abstract
Here, we study the thermoelectric properties of topological semimetal CoSi in the temperature range 300-800 K by using combined experimental and density functional theory (DFT) based methods. CoSi is synthesized using arc melting technique and the Rietveld refinement gives the lattice parameters ofa=b=c= 4.445 Å. The measured values of Seebeck coefficient (S) shows the non-monotonic behaviour in the studied temperature range with the value of ∼-81μV K-1at room temperature. The |S| first increases till 560 K (∼-93μV K-1) and then decreases up to 800 K (∼-84μV K-1) indicating the dominating n-type behaviour in the full temperature range. The electrical conductivity,σ(thermal conductivity,κ) shows the monotonic decreasing (increasing) behaviour with the values of∼5.2×105(12.1 W m-1 K-1) and∼3.6×105(14.2 W m-1 K-1) Ω-1 m-1at 300 K and 800 K, respectively. Theκexhibits the temperature dependency as,κ∝T0.16. The DFT based Boltzmann transport theory is used to understand these behaviour. The multi-band electron and hole pockets appear to be mainly responsible for deciding the temperature dependent transport behaviour. Specifically, the decrease in the |S| above 560 K and change in the slope ofσaround 450 K are due to the contribution of thermally generated charge carriers from the hole pockets. The temperature dependent relaxation time (τ) is computed by comparing the experimentalσwith calculatedσ/τand it shows temperature dependency of 1/T0.35. Further this value ofτis used to calculate the temperature dependent electronic part of thermal conductivity (κe) and it gives a fairly good match with the experiment. Present study suggests that electronic band-structure obtained from DFT provides a reasonably good estimate of the transport coefficients of CoSi in the high temperature region of 300-800 K.
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