Thermal properties Measurement

Thermoelectrics have drawn wide attention recent years. The thermal property measurement lab has facilities to measure thermal conductivity, Seebeck co-efficient and electrical conductivity. Hence the figure of merit could be obtained. Thermal characterization enables one to clearly investigate the sample quality and parameters prior to high pressure investigation at synchrotron.

                  The MMR Seebeck measurement system performs automated measurement of the temperature dependence of Seebeck coefficient for metals, semiconductors and other electrically conductive samples from 300K – 730K using the SB1000 system to measure reference and sample voltages and using the K2000 to stabilize thermal stage temperature. The Seebeck coefficient is measured by comparing the thermoelectric voltage of the unknown sample to the thermoelectric voltage of a reference material (constantan) by heating the thermal stage via a 100Ω resistive heater. Sample mounting requires a rectangular or wire shaped sample approximately 2 – 10 mm in length with a range of thickness from thin films to 1 – 2 mm. The sample is mounted to the thermal stage metal contacts via EpoTek silver-epoxy along with a constantan reference wire. This system provides important characterization of thermoelectric materials at ambient temperature for us in high-pressure studies at synchrotron facilities using the thermoelectric cell assembly designed for the Paris-Edinburgh press. Additionally, this system probes the high-temperature behavior of these materials as thermoelectric efficiency is dependent on temperature. The TPS2500S thermal conductivity measurement system performs automated transient measurements of the absolute thermal conductivity (0.005 to 1000 W/mK) of materials from 300K – 750K using a computer controlled muffle furnace with N2 gas flow for precise control of environment temperature in an inert atmosphere.

The thermal properties are measured via a transient plane source method which provides a heat pulse into the sample and measures the thermal response over an allotted period of time. Ideal sample mounting requires 2 identical samples shaped to either an 8mm diameter cylindrical pellet or a 2mm diameter cylindrical pellet. Options are available to measure single samples with these dimensions; however, there is a loss of accuracy. This system provides characterization of thermoelectric samples at ambient conditions for use in high-pressure studies at synchrotron facilities using the thermoelectric cell assembly designed for the Paris-Edinburgh press. In addition, this system provides the thermal conductivity as a function of temperature which is required to understand thermoelectric efficiency variation with temperature.