Candidate for Magnetic Doping Agent and High-Temperature Thermoelectric Performance Enhancer: Hard Magnetic M-type BaFe₁₂O₁₉ Nanometer Suspension

Abstract

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.

A review of CoSb3-based skutterudite thermoelectric materials

“…The maximum ZT value reached 1.6 at 850 K, increased by 22% compared with that of the matrix (Fig. 11(h [195], © American Chemical Society 2019. double-filled CoSb 3 materials [22]. Co nanoparticles were uniformly dispersed on the grain boundaries and interfaces of the Ba 0.3 In 0.3 Co 4 Sb 12 matrix, as shown in Figs.…”

“…)). Very recently, we also prepared a series of magnetic nanocomposites BaFe 12 O 19 /In 0.25 Co 4 Sb 12 by introducing BaFe 12 O 19 nanometer suspension into the In-filled CoSb 3 matrix material[195]. BaFe 12 O 19 nanometer suspension can not only solve the agglomeration phenomenon of nanoparticles in nanocomposites (Figs.Fig.…”

Impurity Removal Leading to High-Performance CoSb3-Based Skutterudites with Synergistic Carrier Concentration Optimization and Thermal Conductivity Reduction

“…Two A g modes at ∼153.4 and ∼182.6 cm –1 can be observed, which are the longer (A g1 ) and shorter (A g2 ) Sb–Sb stretching vibrations of the Sb 4 rings in skutterudites, respectively. Meanwhile, the other three peaks at 106.7, 133.1, and 170.8 cm –1 can be identified as the optical phonon modes (2F g + E g ) of skutterudites. , Difference in the vibration modes among TGZM-Ce 0.75 Fe 3 CoSb 12 of this study, BaFe 12 O 19 /In 0.25 Co 4 Sb 12 nanocomposite, and Ge/Sn-filling CoSb 3 should be induced by the composition difference, where different fillers might have different influences on the Sb 4 rings and the corresponding vibration modes . To further understand the crystal structure of TGZM-Ce 0.75 Fe 3 CoSb 12 , a typical low-magnification TEM image of TGZM-Ce 0.75 Fe 3 CoSb 12 is displayed in Figure d.…”

“…These fillers can significantly strengthen the phonon scattering to reduce κ l in CoSb 3 -based skutterudites. Particularly, rare-earth Yb and Ce fillers, with heavy atomic masses and small ionic radii, can effectively reduce κ l . , For the p-type CoSb 3 -based skutterudites, the dominating carriers and the corresponding electrical conducting types can be tuned by substitution at the Co or Sb site. − Pandya et al partially replaced Co with Fe, and a p-type Co 0.95 Fe 0.05 Sb 3 was obtained with a room-temperature S of ∼55 μV K –1 and a high S 2 σ of ∼10 μW cm –1 K –2 . Ba-filled and Fe-substituted (at Co sites) BaFe 4 Sb 12 possesses a p-type electrical conducting behavior with a room-temperature S of ∼65 μV K –1 and a zT of 0.62 at 800 K. In addition, Ge substitution at the Sb site forms a p-type Co 4 Ge 0.5 Sb 11.5 with a room-temperature S of ∼50 μV K –1 .…”

Recent Progress in Multiphase Thermoelectric Materials

“…The natural extension of using magnetic elements is to include magnetic phases to enhance the performance of thermoelectric materials [264,269,270]. The magnetic particles of BaFe 12 O 19 in Ba 0.3 In 0.3 Co 4 Sb 12 formed a magnetic composite; BaFe 12 O 19 nanoparticles trap electrons in the ferromagnetic phase due to the spiral motion of the electrons generated by non-uniform spherical magnetic fields.…”