A flexible measurement system for the characterization of thermoelectric materials

The figure of merit needs to be determined to rate the quality of thermoelectric materials (TM). Therefore, it is necessary to measure all involved parameters-the Seebeck coefficient (S), the thermal conductivity (l), and the electrical conductivity (s). Hence, a concept of a measurement system was developed to perform a quick and global characterization of TM by the use of two different sample mounts. The maximum measurement temperature was planned to be at least 600 °C. The first mount contains a four-point measurement system to determine the electrical conductivity. The second one generates a heat flow which could be metered by measuring temperatures at six specified points. In combination with the recorded voltage at two points on the sample, S and l can be calculated at the same time. Because of the strong dependence between contact resistance and contact pressure, the measurement system was designed to keep the pressure constant for a high reproducibility and a small error margin. All measuring points like the commercial spring-mounted pogo-pins and the thermocouples (TC), which are integrated spring-mounted in a special designed capsule, have small variances. Experiments could show that the divergence of the force from the mounting cylinder to the sample is constant and not dependent on the air pressure. Thus, the accuracy of the measurement device was improved by increasing the contact pressure.