engleski

Report on the recent investigations of the systems which assume some of the good thermoelectric properties

We present our recent investigations on physically different systems which assume large thermopower, one of the most important properties of a thermoelectric material: A)YbAl₃ Since it was recognized that YbAl₃, a valence fluctuated system, assumes power factor even higher than Bi₂Te₃ (a semiconductor which is practically the only material used today in thermoelectric (TE) devices), YbAl₃ becomes one of the most interesting and most investigated metallic compound. We present our investigations on the monocrystals obtained by the “self flux method”. It was not noticed some improvement in the TE characteristics, but our investigations indicate possible improvement at high temperatures by doping with Lu. We also cast a new light on the energetic scales of YbAl₃. B) Highly doped polysilicon thin films By heavily doping of polysilicon thin films using the LPCVD method, we can reach into the metallic region of SiB, i.e., the transport properties, thermopower and resistivity, shows metallic like behavior from the lowest temperatures measured 2 K. Above 100 K the transport properties can be described by the theories for metals taking that the Fermi energy is low, i.e., that the terms with (E/E_F)² are not negligible. Due to the low Fermi energy, we obtained for thermopower 200 μV/K at room temperature ; much higher than predicted for the common metals and the same as of Bi2₂Te₃.

thermoelectric materials; polysilicon; valence fluctuated system

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