Abstract:
PbTe based thermoelectric generators are widely employed by the United States Army in
space crafts to supply on-board power, and in pacemakers batteries, it's one among the
widely used thermoelectric semiconductor material with good chemical stability, good
mechanical strength, high melting point, low vapour pressure, and intermediate operating
temperature (900 K). But still, the PbTe module suffers from low efficiency, and
comparatively research on thermoelectric modules is at a primary stage because of the gap
between the material and device technologies. Thermoelectric devices are composed of
different layers, such as electrodes, insulators, thermoelectric elements, and bonding
interfaces. These layers have different physical features, and to construct thermo
mechanically reliable devices. The interfacial reaction between the electrode and the
thermoelectric leg has to be considered. Ni and Fe are commonly used as a diffusion barrier
and electrode for PbTe because the mismatch of coefficient of thermal expansion is very low
comparing with the other materials.in the case of metallization of PbTe with Ni, it was
observed that both Ni-Te intermetallic and voids can form near the bonding interface which
can lead to high electrical and thermal contact resistance. It is also difficult to get a
metallurgical high strength joint with Fe. Fe can only bond at a high temperature which can
affect the property of thermoelectric leg PbTe. We have added the atomic present of Fe to Ni
to investigate the Effect of Fe addition (Ni-at1%, 2at%, 5at %) in the PbTe/Ni interfacial
reaction, and we observed promising results. The experiment is undertaken at different
temperatures and time intervals to study the kinetics and based on our results we conclude
that Ni-5at%Fe /PbTe 700oC/15min is the best one, if we increase beyond 5at%Fe it would
take a longer time to join. The detailed results will be described in chapter 4 of this thesis
