Effect of grain size distribution in raw powders on the thermoelectric and mechanical properties of hot-extruded Bi0.4Sb1.6Te3 and Bi2Te2.85Se0.15 solid solutions

The effect of grain size distribution in raw powders on the structure and properties of n- and p-type conductivity room-temperature thermoelectric materials based on bismuth and antimony chalcogenides has been studied. Mixtures of coarse-grained and fine-grained powders have been used as raw powders. The samples have been produced using hot extrusion. The structure of the powders and the bulk materials has been studied using X-ray diffraction and electron microscopy. The thermoelectric properties of the samples have been examined using the Harman method. The mechanical properties of the samples have been tested by measuring the uniaxial compression ultimate strength. It has been shown that increasing the fraction of fine-grained powder in the raw powder mixture leads to an almost linear increase in the mechanical strength of the extruded material. The optimum grain size distribution that increases the thermoelectric figure of merit of the p-type conductivity materials has been found. A thermoelectric material having the thermoelectric figure of merit ZT =1.02 at 330 K and ZT = 0.9 at 336 K for p- and n-type conductivity, respectively, has been obtained using hot extrusion.