Synthesis and thermoelectric properties of Sn - doped ZrCoBi - based Half - Heusler compounds

In order to study the effect of Sn doping on the structure and thermoelectric properties of ZrCoBi compounds, a series of ZrCoBi_1-xSn_x(x=0, 0.05, 0.10, 0.15, 0.20, 0.25) samples with different doping concentrations were prepared by induction smelting combined with sparking plasma sintering. The phase structure and thermoelectric properties of ZrCoBi_1-xSn_x samples were tested and analyzed. The experimental results show that the synthesized ZrCoBi based compounds are all standard Half-Heusler phase, and the maximum solid solubility of Sn in the ZrCoBi matrix is 20%. At the same temperature, with the increase of Sn doping concentration at the Bi site, the conductivity increases, the Seebeck coefficient increases first and then decreases, and the ZT value increases continuously. By Sn/Bi substitution, the thermal conductivity of ZrCoBi_1-xSn_x is significantly reduced, and the lowest value of the thermal conductivity of ZrCoBi_0.80Sn_0.20sample is 2.56 W·cm^-1·k^-1 around 730 K. Due to the increase of power factor and the decrease of thermal conductivity, the ZT value increases from 0.39 of the undoped ZrCoBi sample to 1.02 of the maximum ZrCoBi_0.20Sn_0.80 sample around 730 K. Sn doping introduces acceptor impurity, optimizes carrier concentration, and improves conductivity and power factor. At the same time, because of the size and mass difference between Sn and Bi atoms, the point defect scattering is enhanced, and the thermal conductivity is further reduced, thus the ZT value is increased and the thermoelectric properties are improved.