ICT2014 Abstracts

In the thermoelectric effect, an entropy current drives an electric current. Depending on the sign of the Seebeck coefficient α of the material, both currents are parallel or anti-parallel. The serial connection of n-type (α < 0) and p-type (α > 0) semiconducting legs with their contacts being alternatingly hot and cold, allows constructing thermoelectric modules, which can make use of the entropy current running from “hot” to “cold” for energy harvesting. Thermoelectric n- and p-type semiconducting oxides were synthesized by sol-gel route for high-temperature application. Oxide ceramics are used because of their thermodynamic stability in the high-temperature range. The designed materials were structurally characterized by X-ray diffraction (XRD) analyses and scanning and transmission electron microscopy including chemical analysis based on electron energy-loss and X-ray emission spectroscopy. Thermoelectric measurements like temperature-depending electronic conductivity σ(T) and Seebeck coefficient α(T) from thermo-voltage were made to investigate the quality of chosen compounds by estimating the power factor α²σ. Analyzed oxide ceramics were prepared to construct a thermoelectric generator for high-temperature application up to 800 °C. The pieces of thermoelectric ceramics were sandwiched between Al₂O₃-plates by fixing them with gold as contacting material for serial electronic connection. Thermoelectric parameters of the module were measured in high-temperature conditions to investigate the reloading of energy from entropy current to electronic current when a temperature difference is applied between the top- and bottom side of the thermoelectric device.