Candidate for Magnetic Doping Agent and High-Temperature Thermoelectric Performance Enhancer: Hard Magnetic M-type...

How to prevent the agglomeration of nanoparticles in nanocomposites remains a key challenge. Using nanometer suspension as a doping agent provides an effective approach to solve this challenge. A new technique that consists of chemical coprecipitation, ball milling and sedimentation separation metheds was developed for preparing hard magnetic M-type BaFe₁₂O₁₉ nanometer suspension. The single-phase BaFe₁₂O₁₉ nanoparticles dispersed uniformly in alcohol have been prepared by this new technique. Magnetic nanocomposite thermoelectric materials with a homogeneous dispersion of BaFe₁₂O₁₉ nanoparticles were prepared through a combination process of an ultrasonic mixing of BaFe₁₂O₁₉ nanometer suspension and In-filled CoSb₃ thermoelectric matrix material and spark plasma sintering. The microstructure analysis of magnetic nanocomposite thermoelectric materials confirmed that using the nanometer suspension as a doping agent is an effective way to solve the agglomeration phenomenon of nanoparticles in nanocomposites. In addition, the decline of thermoelectric performance in the high-temperature intrinsic excitation region of In-filled CoSb₃ can be effectively suppressed by the magnetic phase transition of BaFe₁₂O₁₉ nanoparticles dried by nanometer suspension from ferromagnetism to paramagnetism. It is also confirmed that using the BaFe₁₂O₁₉ nanometer suspension as a thermoelectric performance enhancer is an effective way to solve the challenging problem of performance deterioration of thermoelectric materials at high temperature.