Optimization of Thermoelectric Transport Properties in Nanocomposite MgAgSb-based Alloys

doi:10.15541/jim20250010

Abstract

Abstract:

MgAgSb exhibits excellent thermoelectric performance in the near-room temperature range of 300-573 K, making it a key research focus for p-type materials in recent years. Due to the low level of atomic doping, the improvement of thermoelectric performance through carrier concentration optimization via doping alone is limited. In this study, Nb and Ta nano-secondary phases were introduced into the MgAg_0.97Sb_0.99 matrix, and two series of alloys, xNb/MgAg_0.97Sb_0.99 and yTa/MgAg_0.97Sb_0.99, were prepared using high-energy ball milling mechanical alloying. The introduction of Nb nano-secondary phase significantly altered carrier and phonon transport properties of the material. It was the presence of nano-secondary phase Nb in the 0.005Nb/MgAg_0.97Sb_0.99 alloy that optimized its unique microstructure and electrical performance, achieving a maximum power factor of 24.1 μW·cm^-1·K^-2 at 533 K. Additionally, the introduction of secondary phase enhanced phonon scattering, significantly reducing thermal conductivity. As a result, the 0.005Nb/MgAg_0.97Sb_0.99 sample achieved an optimal zT of 1.09 at 483 K, improved by 9.0% compared to MgAg_0.97Sb_0.99 at the same temperature. Furthermore, the introduction of Ta, a homologue of Nb, into the MgAg_0.97Sb_0.99 sample showed a similar trend, with 0.005Ta/MgAg_0.97Sb_0.99 achieving zT of 1.02 at 483 K. This study demonstrates an effective nanocomposite strategy for optimizing thermoelectric transport properties and enhancing thermoelectric performance of p-type MgAg_0.97Sb_0.99.

Key words: MgAgSb-based compound, secondary phase, alloying, thermoelectric performance

CLC Number:

TQ174

WU Huaxin, ZHANG Qihao, YAN Haixue, WANG Lianjun, JIANG Wan. Optimization of Thermoelectric Transport Properties in Nanocomposite MgAgSb-based Alloys[J]. Journal of Inorganic Materials, 2025, 40(9): 997-1004.

Figures/Tables 6

Fig. 1 Phase compositions of xNb/MgAg0.97Sb0.99 samples (a) XRD patterns; (b-d) Surface scan element distributions of xNb/MgAg0.97Sb0.99 samples when x is (b) 0.005, (c) 0.010, and (d) 0.015

Fig. 2 Electrical properties of xNb/MgAg0.97Sb0.99 alloys (a) Nb content dependent room-temperature carrier concentration and mobility; (b-d) Temperature dependence of (b) electrical conductivity, (c) Seebeck coefficient, and (d) power factor

Fig. 3 Temperature dependence of thermal properties and figure of merit for xNb/MgAg0.97Sb0.99 alloys (a) Total thermal conductivity; (b) Thermal conductivity comprising lattice and bipolar contributions; (c) zT; (d) Comparison of peak zT and average zT. Colorful figures are available on website

Fig. 4 Phase compositions of yTa/MgAg0.97Sb0.99 samples (a) XRD patterns; (b-d) Surface scan element distributions of yTa/MgAg0.97Sb0.99 samples when y is (b) 0.005, (c) 0.010, and (d) 0.015

Fig. 5 Electrical properties for yTa/MgAg0.97Sb0.99 alloys (a) Ta content dependent room-temperature carrier concentration and mobility; (b-d) Temperature dependence of (b) electrical conductivity, (c) Seebeck coefficient, and (d) power factor

Fig. 6 Temperature dependence of thermal properties and figure of merit for yTa/MgAg0.97Sb0.99 alloys (a) Total thermal conductivity; (b) Thermal conductivity comprising lattice and bipolar contributions; (c) zT; (d) Comparison between peak zT and average zT. Colorful figures are available on website

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