Page 39 - Read Online
P. 39
Page 14 of 23 Shanmugasundaram et al. Energy Mater. 2025, 5, 500100 https://dx.doi.org/10.20517/energymater.2024.304
Figure 6. (A-C) Temperature dependence of thermal transport characterization for Ag Mg 1.8-x Zn Sb (x = 0, 0.01, 0.03 and 0.05), (D)
x
2
1.2
comparison of κ with reported work [68,69] .
L
Based on the formation energy, Ag atoms can replace the tetrahedral Mg2/[Mg Sb ] sites and some excess
2-
2
2
Ag atoms occupy the interstitial sites of Mg Zn Sb system . Here, the larger atomic radius of Ag is
[45]
1.8
1.2
2
~165 pm which is lower than Mg (~145 pm), creates mass contraction and enhances the phonon scattering
via point defects. This also causes some lattice distortion via the introduction of various wavelengths (short
2+
+
to long) of lattice defects. The charge imbalance between Mg and Ag creates the formation of Mg
vacancies (produces excess holes), and occupancy of interstitial sites. Therefore, heavier Ag substitution at
+
Mg sites creates V and introduces different types of defects such as point defects, dislocation, stacking
2+
Mg
faults, grain boundaries, and strain in the lattice via atomic dislocations. These defects, identified using
HR-TEM, Inverse Fast Fourier Transform (IFFT), and subsequent strain analysis, strengthen the phonon
transport properties [45,67] .
