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Influence of zinc content and grain size on enhanced thermoelectric performance of optimally doped ZnSb
Journal
Materials Research Bulletin
ISSN
00255408
Date Issued
2022-05-01
Author(s)
Biswas, Rajan
Vitta, Satish
Dasgupta, Titas
Abstract
ZnSb is a promising mid-temperature, low-cost thermoelectric (TE) material. Lowering lattice thermal conductivity by grain-size reduction or introducing low thermal-conducting phases (β-Zn4Sb3) in optimally doped ZnSb was the objective of this work. Co-doped compositions - (Zn0.998Ag0.002)1+xSb0.99Sn0.01 (x = 0, 0.05, 0.1 and 0.2) have been synthesized by melting - rapid compaction - annealing process. One set of samples were ball-milled before compaction. The Zn-loss is adjusted with increasing excess-Zn (x), which forms the β-Zn4Sb3 phase in the non-ball-milled batches. Our results show that the co-doping technique can result in excellent TE performance with a peak figure-of-merit value of 1.17 at 640 K and efficiency of 10.3% at a gradient of 350 K. Efficiency can be further increased to 10.9% (even equal to the highest reported in β-Zn4Sb3) incorporating excess-Zn for x = 0.2. However, grain-size reduction to the submicron range is ineffective as phonons with lower mean-free-path substantially contribute to heat conduction in ZnSb.
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