Temperature dependence of the Seebeck coefficient and the potential barrier scattering of n-type PbTe films prepared on heated glass substrates by rf sputtering

Abstract

Thermoelectric properties of polycrystalline degenerate n-type PbTe films have been investigated in order to understand potential barrier scattering. The Seebeck coefficients of the PbTe films obtained in this study were larger than those of bulk samples having the same carrier concentrations in the temperature range from 100 to 450 K. Some of their power factors were larger than those of bulk samples having the same carrier concentrations in the temperature range from 200 to 450 K, while their electrical conductivities were smaller than those of bulk samples. From a comparison of these results with those previously reported, we concluded that potential barrier scattering occurred at grain boundaries in our films, resulting in the above favorable changes in thermoelectric properties. By analyzing their properties using the energy filtering model, we estimated the height of grain-boundary potential barriers, which probably influenced the increases in the Seebeck coefficient. We also examined the origin of the potential barriers accordingly. Consequently, we consider that the origin of the potential barriers was mainly due to point defects, probably Te vacancies, and that the barrier height may be controlled, for example, by the preparation conditions.

Control of thermoelectric properties in ZrO2/CoSb3 nano‐dispersed composites

“…The presence of nano-sized ZrO 2 hardly affects the Seebeck coefficient, especially at high temperatures, where a maximum is forming near 720 K. The slight change in the Seebeck coefficient of the composites could be attributed to grain-boundary scattering of the charge carriers as reported elsewhere [11], whereas no clear systematic relation to the ZrO 2 content is observed here. In general, potential barriers can be formed by localized states linked to lattice imperfections such as point defects and dislocations at grain boundaries [12]. It is noted that ceramic inclusions themselves cannot be the reason for an increase of the Seebeck coefficient.…”

Nano Bulk Thermoelectrics: Concepts, Techniques, and Modeling

“…Several research groups have reported the implementation of this technique for n-type and p-type Si 0.8 Ge 0.2 and some types of Bi x Sb 2Àx Te 3 [41,42,70]. Spark plasma sintering [71][72][73] is a newer technique compared with conventional sintering approach where the heat is provided by an external source. In this method the heat is generated by passing a pulsed DC current through a die and conductive powder.…”

Seebeck effect of as‐grown and micro‐structured metallic (Zn,Al)O

“…At first sight, this appears to be a minor effect. However, keeping in mind that in metallic samples, such as Zn 0.98 Mn 0.02 O, only a small fraction of the free carriers in the vicinity of the Fermi-level E F contributes to the transport and, moreover, that the potential barriers due to the grain boundaries define an additional minimum energy E min for transport to take place [10], this reduction of the carriers due to the additional traps has a significant impact. It reduces the number of occupied conduction band states and lowers the global Fermienergy, i. e. it mainly changes the carrier distribution at E F which provides the carriers participating in the transport processes.…”