Ab initio study of thermodynamic and thermoelectric properties of the paramagnetic p-type half Heusler XNiBi (X=Sc, Y)

The primary aim of this scientific study is to investigate the thermodynamic and thermoelectric characteristics of paramagnetic p-type XNiBi (X = Sc and Y) half-Heusler compounds, which possess 18 valence electrons. The calculations were conducted utilizing the density functional theory (DFT), implemented in the WIEN2k code. Subsequently, the Boltzmann transport equation (BTE) was solved, employing an approximation of constant relaxation time (CRTA) to analyze the thermoelectric properties. Additionally, Debye’s quasi-harmonic equation was employed to assess the thermodynamic properties. The investigated compounds exhibit dynamic stability, suggesting the possibility of their experimental synthesis. The analysis of their thermodynamic properties indicates that these compounds possess the ability to store heat, as evidenced by their heat capacity and Debye temperature. Regarding the thermoelectric behavior of the alloys, we employed Slack’s model to calculate the thermal conductivity. Our findings demonstrate that both compounds show p-type behavior. Notably, the thermoelectric figure of merit (ZT) reaches its highest values, 0.17 for ScNiBi and 0.186 for YNiBi, within the temperature range of 400 K to 800 K. Therefore, we recommend and propose the utilization of ScNiBi and YNiBi compounds as thermoelectric materials, particularly in the low to medium temperature range. Graphical abstract