Thermoelectric
materials are used in thermoelectric device for generating cooling and heating
effects. The most common uses of these materials are to regenerate the
electricity from waste heat at electric power plants. These are available as
per high strength or low cost materials. The low cost materials which have
strong sufficient thermoelectric effect are used in applications including
power generations and refrigeration. We mostly use in such applications bismuth
telluride (Bi2Te3)
thermoelectric material.
Basically
for manufacturing high quality thermoelectric module, the selection of
thermoelectric material is affected by several factors such as:
·
Electrical
Conductivity
·
Thermal
Conductivity
·
Seebeck
Coefficient
·
Temperatures
Change Behavior
After choosing a material its usefulness is
decided by the material’s power factor and device efficiency.
As
most of the company use high-efficiency material Bi2Te3
and high temperature solders for generating thermoelectric modules, so we
discuss about this in detail.
Bismuth Telluride (Bi2Te3):
It
is a grey powder which is compounded from bismuth and tellurium. We also know
this as bismuth (lll) telluride. For portable power generation and
refrigeration we alloy this thermoelectric material with antimony and selenium
in a semiconductor. It is also known as topological insulator and hence
exhibits many thickness dependent physical properties.
Why use as thermoelectric
material?
Bismuth
telluride has a thin gap layered semiconductor which has trigonal unit cell.
Due to van der waals bonding, it cleaves easily along with trigonal axis
between neighboring tellurium atoms. Because of this feature we always use
polycrystalline bismuth telluride (Bi2Te3)
for power generation and cooling applications. Apart from this, the Seebeck
coefficient of bismuth telluride metal becomes compensated around the room
temperature. Due to which it is forced to be used in power generating devices
and having the alloy of bismuth, antimony, tellurium and selenium.
As
bismuth telluride thermoelectric material and its solid solutions are good at
room temperature, hence, it is also suitable for refrigeration applications
around 300 K. A method named Czochralskiis used to grow single crystalline
bismuth telluride compounds. These compounds are produced with directional
solidification from melt or powder metallurgy processes. The produced material
has superior mechanical properties and sensitive to structural defects and
lower impurities due to high optimal carrier concentrations.For more information visit @
