Thermomagnetic Performance of Polycrystalline TaSb2

doi:10.15541/jim20250264

Abstract

Abstract:

Thermomagnetic refrigeration based on the Ettingshausen effect is a low-temperature solid-state cooling technology with advantages of precise temperature control, compact size and noiseless operation. In recent years, topological semimetals, which possess both electrons and holes as charge carriers and exhibit high carrier mobility, have shown excellent thermomagnetic performance at low temperatures, making them promising candidates for cryogenic applications. In this study, highly dense polycrystalline TaSb₂ was synthesized via solid-state reaction followed by spark plasma sintering, and its low-temperature thermomagnetic transport properties were systematically investigated. The results show that the Nernst thermopower (S_yx) peaks at around 27 K and increases with applied magnetic field. Under 9 T and 26 K, the Nernst power factor ((PF)_N) reaches 315.1 μW·cm^-1·K^-2, while under 9 T and 22 K, the Nernst figure of merit (z_N) is 7.1×10^-4 K^-1, both outperforming most reported polycrystalline thermomagnetic materials. Mechanistic analysis indicates that the high performance originates from the combined effects of strong bipolar effect, high carrier mobility and significant phonon-drag enhancement of thermopower. Moreover, magnetic fields markedly suppress the electronic contribution to thermal conductivity at low temperatures, making the total thermal conductivity predominantly determined by the lattice component. This work offers a new material option and design strategy for low-temperature solid-state cooling applications. The relatively high lattice thermal conductivity partially limits the thermomagnetic performance, and further reduction via phonon engineering could lead to substantial improvements.

Key words: topological semimetal, polycrystalline TaSb₂, thermomagnetic effect, bipolar effect, phonon drag

CLC Number:

TB34

LI Peng, QIU Pengfei, JIANG Binbin, XIAO Jie, SHI Xun. Thermomagnetic Performance of Polycrystalline TaSb₂[J]. Journal of Inorganic Materials, 2026, 41(3): 303-310.

Figures/Tables 5

Fig. 1 Crystal structure, band structure and phase analysis of polycrystalline TaSb2 (a) Schematic representation of the unit cell; (b) Band structure with spin-orbit coupling considered; (c) Powder XRD pattern and Rietveld refinement results; (d) Secondary electron images of cross-section after acid pickling (upper left) and polished surface (upper right), and corresponding elemental mappings (lower)

Fig. 2 Electrical transport properties of polycrystalline TaSb2 Temperature dependences of (a) Seebeck thermopower Sxx, (b) Nernst thermopower Syx, (c) electrical resistivity ρyy, and (d) Nernst power factor (PF)N of polycrystalline TaSb2 under different magnetic fields

Fig. 3 Analysis of the electrical transport properties of polycrystalline TaSb2 (a, b) Comparison between experimental data and two-carrier model fitting results for (a) resistivity ρyy and (b) Hall resistivity ρyx of polycrystalline TaSb2 (dots representing experimental data and lines representing fitting results); (c) Temperature dependences of electron concentration ne and hole concentration nh in polycrystalline TaSb2 with inset showing temperature dependences of electron mobility μe and hole mobility μh; (d, e) Comparison between experimental and theoretical values of Nernst thermopower Syx at (d) low temperatures (15, 25, 35 and 50 K) and (e) high temperatures (above 150 K); (f) Contributions of thermal diffusion and phonon drag to the thermopower of electrons (${S}_{\text{d}}^{\text{e}}$ and ${S}_{\text{p}}^{\text{e}}$) and holes (${S}_{\text{d}}^{\text{h}}$ and ${S}_{\text{p}}^{\text{h}}$)

Fig. 4 Thermal transport properties and performance evaluation of polycrystalline TaSb2 (a) Temperature dependence and (b) magnetic field dependence of thermal conductivity κxx of polycrystalline TaSb2; (c) Temperature dependence and (d) magnetic field dependence of Nernst figure-of-merit zN of polycrystalline TaSb2

Table 1 Parameters used to fit the thermal electric conductivity of polycrystalline TaSb2

T/K	κ_l/(W·m^-1·K^-1)	κ_c(0, T)/(W·m^-1·K^-1)	η/T^-1	s
5	1.17	5.92	1.190	1.41
15	13.71	11.68	0.790	1.58
25	36.81	12.72	0.400	1.54
50	45.83	9.26	0.114	1.45
100	29.66	7.14	0.043	1.56
150	21.47	7.85	0.033	1.88
200	17.51	8.34	0.029	1.81
250	15.49	8.41	0.026	1.91
300	14.90	8.53	0.023	1.90

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Thermomagnetic Performance of Polycrystalline TaSb₂

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