Potential-Seebeck-microprobe (PSM): measuring the spatial resolution of the Seebeck coefficient and the electric potential

Thermoelectric power generators are typically operating in a large temperature difference; indeed the properties of thermoelectric semiconductors vary with temperature. Thus the overall conversion efficiency is strongly dependent on spatial variations of the material properties according to the temperature profile along the entire thermoelectric generator element. Similarly, a functionally graded module is capable of accomplishing thermal sensors with linearised characteristics over a wide temperature range. The Seebeck-coefficient S is a measure of the electrically active components in a material. Different components in a single unit become visible by measuring the local S with a scanning thermoprobe. This applies accordingly for the electrical conductivity and therefore the behaviour of the material in a certain temperature gradient becomes predictable. A scanning Seebeck microprobe has been combined with the measurement of the electric potential along the surface of semiconducting or metallic material. A heated probe tip is placed onto the surface of the sample under investigation, measuring the Seebeck coefficient. Using a specially designed sample holder, an AC current can be applied to the specimen, allowing for the detection of the voltage drop between one current contact and the travelling probe tip. This voltage is proportional to the electrical conductivity at the tip position. With this technique a spatially resolved imaging of the Seebeck coefficient as well as the electrical conductivity can be performed. Furthermore the electrical contact resistance between different materials becomes visible, e.g., in segmented thermoelectric or other devices.