When i plotted the Seebeck coefficient with temperature for Si, Ge and ZnS the curves show little convex. Can anyone help me to explain the Physics behind this?
The seeback coefficient is proportional to [T d(ln(\sigma))/dE] where \sigma is the electrical conductivity. When T> 300 K the electron mobility decreases (\sigma = e*n*\mu), thus d(ln(\sigma))/dE decreases. Thus the above curve is convex.
Hello Sangay,
additionally to Valentin's answer I remark:
I would apply the approximation of Strattons formulae (low doped semiconductors):
S = -(e/k)*[2,5 + r - eta]
e - charge ; k - Boltzmann constant ; r - scattering parameter
eta = (EF - Ec]/kT
EF - Fermi energy ; Ec - band edge energy
Eta varies with 1/T. Therefore (the amount of) S decreases with increasing T as found by you.
With Regard
R. Mitdank
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