Abstract:
The growing demand for energy needs better materials for energy conversion. One class of
materials to address the problem are materials for conversion of waste heat to electricity, which
are called thermoelectric materials. Even though SnTe and Bi2Te3 are important thermoelectric
materials, the phase diagram and microstructural studies of their pseudo-binary system are not
well investigated. Since these microstructures can determine the property of the material,
investigation of the relationship between microstructure and thermoelectric property of Sn-Bi-Te
system is anticipated to result in the finding of new thermoelectric material. Therefore, this
research is aimed to study the variation of microstructures with the composition of selected
samples. The thermoelectric properties have been investigated as a function of variation in
microstructures.
This research contains two parts. The first part aims at determining the effect of Bi addition to the
SnTe system. It includes investigation of the microstructural, mechanical and thermoelectric
properties of the system. This work describes the nature of the microstructure of the system. The
study of the mechanical property concerns the change of Vickers hardness with aging heat
treatment. The study of the thermoelectric properties was as a function of both composition and
temperature. This group samples had created small SnTe phases compacted with Bi. Such a
structure has a high probability of scattering phonon while allowing electrical conduction and
hence enables the high value of the Seebeck coefficient.
The second part considers a group of samples which were studied to investigate the relatively
complex nature microstructure of the SnTe - Bi2Te3 system. It focuses on the region where Bi2Te3
is soluble in SnTe. Both composition and processing methods result in the creation of different
kind of microstructures. The study of the microstructure in this region focuses on determining the
phases and crystal structure of the system. This part of the research aims at exploring different
compositions which have a high potential for thermoelectric application.
