Abstract:
Typical alloy development of a eutectic, compositional system of Ag18.34Bi29Te52.66 (at.%) was
successfully obtained by alloying very pure elemental raw materials, viz., Silver, Bismuth, and
Tellurium by flame melting. The obtained master ingot processed by Twin-roll casting with varied
rollers speed from slow to fast (600-2400 rpm) by keeping the rest parameters, viz., the gap
between rollers, cooling rate, the distance of head melt to rollers, melting temperature, the
dimension and loads of rollers constant. Very thin and silvery stripes obtained from the casting
process with different thickness sizes depending on the casting rollers speed. The stripes were
ground into raw powder, and sintered by a spark plasma-sintering unit. The relative density of
the sintered samples measured by Archimedes methods and all samples density measurement
result was above 95%. As the examination result of a scanning electron microscope, the structures
are multidirectional, unlike to other results that processed by another equilibrium process. Again,
the structures are with refined grain size, and due to increased grain boundaries density, the
cumulative material’s thermal conductivity became lowered and with moderate power-factor to
result in improved thermoelectric performance and evidenced by peak ZT of 1.18 at 303K that
corresponds to low revolution per minute (600 rpm) processed sample. The achievement of this
work can reported as, due to increasing rate of solidification with the increasing casting rollers
speed, the Bi2Te3 phases become amorphous as witnessed by the X-ray diffraction pattern.
Therefore, with increasing rollers speed, the transport properties decrease as seen from each
measured and calculated value, and leading to decreasing total thermoelectric performance
efficiency.
