ABSTRACT
Thermoelectric materials are widely used in refrigeration chips, thermal power generation, catalysis and other fields. Mg3Bi2-based thermoelectric material is one of the most promising thermoelectric materials. Herein, the Mg3Bi2-based samples were prepared by high temperature synthesis, and the influence of Mg/Sb content on the electrical transport properties and semi-conductivity/semi-metallicity of the materials has been studied. The results indicate that the efficiency of introducing electrons from excess Mg prepared by high temperature synthesis is lower than that introduced by ball milling, due to the high vapor pressure of Mg. The doping of Sb/Te at the Bi site would make it easier for the material to change from p-type conduction to n-type conduction. With the increase in Mg content, the semi-conductivity of the material becomes weaker, the semi-metallicity becomes stronger, and the corresponding conductivity increases. With the increase in Sb content, the samples exhibit the opposite changes. The highest power factor of ~1.98 mWm-1K-2 is obtained from the Mg3.55Bi1.27Sb0.7Te0.03 sample.
ABSTRACT
BiCuSeO has great application prospects in thermoelectric power generation and thermoelectric catalysis, but it is limited by its lower thermoelectric performance. Herein, BiCuSeO bulk materials were prepared using a solid-phase reaction method and a ball-milling method combined with spark plasma sintering, and then the thermoelectric properties were improved by synergistically increasing carrier concentration and mobility. Al was adopted to dope into the BiCuSeO matrix, aiming to adjust the carrier mobility through energy band adjustment. The results show that Al doping would widen the bandgap and enhance the carrier mobility of BiCuSeO. After Al doping, the thermoelectric properties of the material are improved in the middle- and high-temperature range. Based on Al doping, Pb is adopted as the doping element to dope BiCuSeO to modify the carrier concentration. The results show that Al/Pb dual doping in the BiCuSeO matrix can increase the carrier concentration under the premise of increasing carrier mobility. Therefore, the electrical conductivity of BiCuSeO can be improved while maintaining a large Seebeck coefficient. The power factor of Al/Pb doping reached ~7.67 µWcm-1K-2 at 873 K. At the same time, the thermal conductivity of all doped samples within the test temperature range maintained a low level (<1.2 Wm-1K-1). Finally, the ZT value of the Al/Pb-doped BiCuSeO reached ~1.14 at 873 K, which is ~2.72 times that of the pure phase, and the thermoelectric properties of the matrix were effectively improved.
