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Page 18 of 23 Shanmugasundaram et al. Energy Mater. 2025, 5, 500100 https://dx.doi.org/10.20517/energymater.2024.304

Figure 8. Temperature dependence of (A) κ at 303K, 503 K, and 753 K (B) power factor vs. zT (C) figure of merit of Ag Mg 1.8-x Zn Sb 2
L
x
1.2
(x = 0, 0.01, 0.03 and 0.05) and (D) zT comparison [28,36,37,74-77] .
Figure 9 represents the TE efficiency (η) vs. zT of Ag Mg Zn Sb sample with temperature difference
2
0.03
1.77
1.2
(303-753 K). The maximum η has been expressed as . The theoretical η is determined by
the calculated zT of the prepared sample and the temperature difference between cold (T ) and hot sides
c
(T ). Here, the maximum TE efficiency of 4.9% has been achieved for Ag Mg Zn Sb sample with
0.03
2
1.77
1.2
h
comparable zT (0.5 K at 753 K).
CONCLUSION
In summary, p-type Mg Zn Sb and Mg Ag Zn Sb (x = 0.01 - 0.05) solid solutions have been successfully
2
1.2
1.2
1.8
2
x
1.8
prepared using spark plasma sintering process and their TE transport properties have been investigated. By
Ag substitution on the anion Mg2 lattice, the n and μ were enhanced, resulting in a VB convergence that
leads to narrowed E . Thus, the substantially enhanced σ and a noticeably high PF of 456 μW/mK at 753 K
2
g
were attained in the Ag substituted samples. Moreover, a greatly suppressed κ of 0.56 W/mK at 753 K is
L
also realized due to increased atomic disorder resulting from introduced point defect scattering by Ag,
which scatters different wavelengths of phonons. Consequently, remarkable TE performance with a peak zT