Thermoelectric (TE)
materials have consistently gained momentum
for use in waste heat utilization technology. Recently, we fabricated
a Cu3AlSnS5 (CATS) nanobulk by pelletizing chemically
synthesized CATS nanocrystals using a pulsed electric current sintering
technique and found that it possesses exceptionally low lattice thermal
conductivity (κlat). However, the total thermal conductivity
of the CATS nanobulk was relatively high because of the high carrier
thermal conductivity (κcar) owing to its considerably
high electrical conductivity. In this study, the effect of Ga substitution
in Cu3Al1–x
Ga
x
SnS5 nanobulk materials on the carrier
transport properties of the materials is systematically investigated.
The value of the dimensionless figure of merit ZT of the Cu3Al1–x
Ga
x
SnS5 nanobulk at x = 0.5 (ZT = 0.26 at 665 K) was found to be more
than twice that of the pristine CATS nanobulk at 665 K, primarily
because of the significant reduction in κcar. A detailed
analysis of the correlation among transport parameters, crystal structure,
and thermoelectric performance of the Cu3Al1–x
Ga
x
SnS5 nanobulks
(0.25 ≤ x ≤ 1) revealed that a larger
fraction of the zinc blende (ZB) phase leads to a higher power factor.
In summary, the Cu3Al0.5Ga0.5SnS5 nanobulk exhibited the highest ZT value
in the range of 0 ≤ x ≤ 1 because of
its significantly reduced κcar value as compared
with the CATS nanobulk. This reduced κcar value is
owing to the Ga substitution and the highest ZB phase fraction, resulting
in the highest power factor among the Cu3Al1–x
Ga
x
SnS5 nanobulks
(0.25 ≤ x ≤ 1).