Enhanced Thermoelectric and Mechanical Properties in Yb_0.3Co₄Sb₁₂ with In Situ Formed CoSi Nanoprecipitates

Abstract

Filled Skutterudites are one group of the most promising thermoelectric materials in real power generation applications. Herein, homogeneously dispersed multiscale CoSi nanostructures are successfully embedded into grains of the classic skutterudite system, Yb0.3Co4Sb12, by the in situ precipitation method. Such nanoprecipitates contribute much to the synergistic enhancement of thermoelectric and mechanical properties. On one hand, by the fine deployment of multiscale CoSi nanoparticles, the lattice thermal conductivity is significantly depressed almost to the theoretical limit because of the disrupted propagation of the heat‐carrying phonons at phase boundaries. On the other hand, low‐energy electrons are effectively screened due to the energy filtering effect by the interfacial potential barrier between the CoSi nanoprecipitate and the matrix, resulting in an enhanced power factor. Taken together, an enhanced peak ZT value of ≈1.5 at 873 K for the Yb0.3Co4Sb12/0.05CoSi composite is obtained with a high average ZT ≈0.95 between 300 and 873 K through decoupling the electrical and thermal transport parameters. Moreover, such a microstructure with multiscale CoSi nanoparticles shows significantly improved mechanical properties owing to particle hardening, making it more competitive for practical applications.

A review of CoSb3-based skutterudite thermoelectric materials

“…The electron is not easy to be scattered because of the size of the nanoscale second-phase is much larger than the mean free path of the electron, which has little effect on the electrical properties. The preparation of CoSb 3 -based nanocomposites by in-situ generation [78,[167][168][169][170][171][172][173][174][175][176][177] or mechanical addition of nanoinclusions [178][179][180][181][182][183][184][185][186][187][188][189][190][191][192][193] is a common method to introduce the second phase. In x Ce y Co 4 Sb 12 nanocomposites containing in-situ formed InSb nanophases (10-80 nm) were prepared by melt quenching, annealing, and spark plasma sintering [78], as shown in Figs.…”

“…In addition, introducing nanoscale second-phase into CoSb 3 -based materials to form nanocomposites can not only significantly reduce the thermal conductivity, but also may significantly affect the mechanical properties [158,177,[197][198][199][200][201] of CoSb 3 -based materials. Rogl and Rogl [199] reviewed systematically that nanoparticles can obviously change the mechanical properties of skutterudite TE materials.…”

“…The mechanical properties of different kinds of CoSb 3 -based nanocomposites were obviously changed by introducing some nanoparticles like Yb 2 O 3 [158], TiN [181,200], CoAl [197], CoSi [179], and SiC [198]. Qin et al [177] prepared Yb 0.3 Co 4 Sb 12 with in situ formed CoSi nanoprecipitates by adding the extra Co and Si. Microstructure with multiscale CoSi nanoparticles shows that mechanical properties (hardness and indentation fracture toughness) were significantly improved owing to particle hardening, making it more competitive for practical applications.…”

High thermoelectric figure of merit in well optimized YbyCo4Sb12

“…Improved maximum ZT values ranging from 1.4 to 1.8 were recently reported in the AyCo4Sb12 (A = Sr, In, Ba, La, Ce, Yb) skutterudites by introduction of extra phonon scattering processes arising from multifilling the antimony icosahedra by several different electropositive elements 12 or from nanostructuration (grain boundaries, nanoprecipitates…) 10,[13][14][15][16][17][18][19] or by a combination of both [20][21][22][23] .…”

A material catalogue with glass-like thermal conductivity mediated by crystallographic occupancy for thermoelectric application

“…[3][4][5] The dimensionless thermoelectric figure of merit (ZT), defined as ZT = (S 2 σ/κtot)T, dominates the conversion efficiency, where S, σ, κtot, and T are Seebeck coefficient, electrical conductivity, total thermal conductivity (including lattice thermal conductivity κlat and electronic thermal conductivity κele) and absolute temperature, respectively. κele usually follows the Wiedemann-Franz law, linearly proportional to σ and T. Considering the intertwined or contradicted thermoelectric parameters (S, σ, and κele), 6 optimizing the charge carrier concentration [7][8][9] or suppressing κlat through nano-microstructural engineering [10][11][12][13][14][15] is the common method to increase ZT. Please do not adjust margins Please do not adjust margins Alternatively, discovering materials with the intrinsically low κlat is another important route for achieving high ZT in thermoelectrics.…”