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Page 6 of 20 Hamawandi et al. Energy Mater. 2025, 5, 500065 https://dx.doi.org/10.20517/energymater.2024.204

Electrical and thermal transport property evaluations
The TE transport measurements were conducted on SPS compressed pellets. The total thermal conductivity
κ was estimated using κ = C ·α·ρ, where C is the specific heat capacity, α is thermal diffusivity, and ρ is
p
p
tot
tot
the density of mass. C measurements were performed via Differential Scanning Calorimetry (DSC, PT1000
p
Linseis). The α was measured on 2 mm thick disk-shaped samples (see Supplementary Figure 3 for sample
geometry) using the laser flash analysis (LFA 1000, Linseis) system. σ and S measurements were performed
simultaneously using the commercial ZEM3 ULVAC-RIKO system. A percentage error of 5%-10% is
possible in calculating the thermal conductivity of Bi Te and Sb Te pellets using the laser flash method and
3
2
2
3
can vary due to several factors, including sample quality and measurement precision [38,39] .
Data analysis by reverse Monte Carlo simulations
Experimental extended X-ray absorption fine structure (EXAFS) spectra were extracted from X-ray
[40]
[41]
absorption spectra using the XAESA code , following the conventional procedure . The analysis of
EXAFS spectra employed the RMC method based on the evolutionary algorithm (RMC/EA) implemented
in the EvAX code [42,43] . The RMC method is an atomistic simulation approach that iteratively minimizes the
difference between experimental and calculated EXAFS spectra, making random atomic displacements
within the structure model of the material.

In this study, an initial structure model was constructed for each temperature point based on lattice
parameters from the neutron diffraction data . A supercell (4a × 4b × 3c) containing 720 atoms with
[44]
periodic boundary conditions was used for calculations. The RMC/EA calculations were performed for 32
atomic configurations simultaneously. At each iteration, all atoms in the supercell were randomly displaced
with a maximum allowed shift of 0.4 Å. The configuration-averaged EXAFS spectra were calculated using
the ab initio self-consistent real-space multiple-scattering (MS) FEFF8.5L code [45,46] , considering
contributions from single, double, and triple scatterings. The complex energy-dependent exchange-
correlation Hedin-Lundqvist potential was employed to account for inelastic effects . The amplitude
[47]
scaling parameter is set to 1. Good agreement between experimental and simulated data was achieved in
both k- and R-spaces simultaneously for two absorption edges (Sb/Bi and Te). This was demonstrated by
comparing the Morlet wavelet transform (WT) of the respective EXAFS . RMC/EA calculations for Bi Te
[48]
2
3
-1
and Sb Te were performed in the k-space range of 3.0-15.4 Å and the R-space range from 2 to 7.0-7.6 Å for
3
2
both (Sb/Bi and Te) metal edges. Note that such a wide range in R-space allows one to determine the partial
radial distribution functions (RDFs) g(r) of up to about 8 Å. The convergence of each RMC simulation was
achieved after several thousand iterations. Five RMC/EA simulations with different sequences of pseudo-
random numbers were performed for each experimental data set. As a result of simulations, 3D structure
models of the tellurides were obtained at each temperature point and used to calculate the partial RDFs g(r)
and the average interatomic distances and the mean-square relative displacement (MSRD) factors, also
known as the Debye-Waller factors. The temperature dependencies of the MSRD factors for the nearest and
distant coordination shells were further utilized to estimate the effective force constants (f).

RESULTS AND DISCUSSION
Structural analysis
Through MW-assisted thermolysis, it has been possible to synthesize nanostructured materials in an energy
and time-efficient manner. The synthesis process took about 6 min, with a reaction yield of 98%. Structural
analysis was performed using XRPD on as-synthesized powders, and after their sintering using SPS. The
diffraction patterns of as-made and sintered samples are presented in Figure 2, where the diffraction
patterns are normalized for the most intense diffraction indexed to the (015) plane. For the sintered pellet
samples, the XRPD analysis was conducted on the surface perpendicular to the sintering direction. The