Fine-Grained Bi–Sb Ribbons with Modulation-Doped FeSb Nanoparticles for High-Temperature Cryogenic Applications

Abstract

With about two-thirds of global energy being lost as waste heat, improvement in the mutual conversion of heat and electrical energy is a "must" with the continued growth in demand. The present report investigates the dramatic improvement of thermoelectric performance (ZT) in a well-studied system by utilizing the intrinsic magnetic field generated from within the material. The concept was to utilize the intrinsic magnetic field induced by the randomly dispersed multisized magnetic (FeSb) nanoparticles spread throughout the host TE material (Bi−Sb). It thus modified the transport properties, i.e., electrical/thermal conductivity and Seebeck coefficient, so as to give a record jump of ∼155% in the peak ZT of the referenced material and increased it to 0.79 from 0.32. Interestingly, the application of an external magnetic field further increased the ZT by ∼57% (i.e., from 0.79 to 1.26), thus giving an overall improvement of ∼300% (from 0.32 to 1.26) as compared to the referenced material. What is particularly exciting is that this simple idea of modulation doping of ferromagnetic nanoparticles can also be extended to other important thermoelectric materials.

Advancing Cryogenic Cooling with Self-Modulated YbAgCu4 for Enhanced Thermoelectric Efficiency below Liquid-Nitrogen Temperatures

“…We used a similar methodology in one of our recent work on cryogenic cooling application, where we reported 3-fold-gains in ZT of FeSb nanoparticles based modulation-doped fine-grained Bi− Sb ribbons. 43 Self-modulation could be considered as the single-phased analogue of modulation-doping which involves creating a heterogeneous nanocomposite of a particular material by condensing its highly crystalline polycrystals in the matrix of lower crystalline order (of same phase). As a result, in such structures, highly crystalline, nanosized polycrystals are dispersed three-dimensionally, forming island-like structures within the matrix of lower crystalline order.…”

“…On this line, we endeavor to study the thermoelectric properties of the self-modulated YbAgCu 4 nanostructure by sequentially applying arc-melting, melt-spinning (MS), and spark-plasma-sintering (SPS) approaches together. We used a similar methodology in one of our recent work on cryogenic cooling application, where we reported 3-fold-gains in ZT of FeSb nanoparticles based modulation-doped fine-grained Bi–Sb ribbons . Self-modulation could be considered as the single-phased analogue of modulation-doping which involves creating a heterogeneous nanocomposite of a particular material by condensing its highly crystalline polycrystals in the matrix of lower crystalline order (of same phase).…”