Effect of hydrostatic pressure and alloying on thermoelectric properties of van der Waals solid KMgSb: An \textit{ab-initio} study

Abstract

Through a combined first-principles and Boltzmann transport theory, we systematically investigate the thermal and electrical transport properties of the unexplored ternary quasi two-dimensional KMgSb system of KMgX (X = P, As, Sb, and Bi) family. Herein, the transport properties of KMgSb under the application of hydrostatic pressure and alloy engineering are reported. At a carrier concentration of $\sim 8\times 10^{19}\mathrm{c}{\mathrm{m}}^{-3}$, the figure of merit zT ($\sim 0.75$) for both the $n$-type and $p$-type of KMgSb closely matched, making it an attractive option for engineering both legs of a thermoelectric device using the same material. This is particularly desirable for high-performance thermoelectric applications. Furthermore, the zT value increases as pressure decreases, further enhancing its potential for use in thermoelectric devices. In the case of substitutional doping (replacing 50 \% Sb by Bi atom), we observed $\sim 49\%$ (in-plane) increase in the peak thermoelectric figure of merit (zT). The maximum zT value obtained after alloy engineering is $\sim 1.45$ at 900~K temperature. Hydrostatic pressure is observed to be a great tool to tune the lattice thermal conductivity (${\kappa }_L$). We observed that the negative pressure-like effects could be achieved by chemically doping bigger-size atoms, especially when ${\kappa }_L$ is a property under investigation. Through our computational investigation, we explain that hydrostatic pressure and alloy engineering may improve thermoelectric performance dramatically.

10 pages, 8 figures, and Supplementary Information

References in corpus (5)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Distribution of phonon lifetime in Brillouin zone
• Efficient calculation of carrier scattering rates from first principles
• Physical properties of KMgBi single crystals