Abstract
AbstractEffective medium theories (EMT) are powerful tools to calculate sample averaged thermoelectric material properties of composite materials. However, averaging over the heterogeneous spatial distribution of the phases can lead to incorrect estimates of the thermoelectric transport properties and the figure of merit ZT in compositions close to the percolation threshold. This is particularly true when the phases’ electronic properties are rather distinct leading to pronounced percolation effects. The authors propose an alternative model to calculate the thermoelectric properties of multi‐phased materials that are based on an expanded nodal analysis of random resistor networks (RRN). This method conserves the information about the morphology of the individual phases, allowing the study of the current paths through the phases and the influence of heterogeneous charge transport and cluster formation on the effective material properties of the composite. The authors show that in composites with strongly differing phases close to the percolation threshold the thermoelectric properties and the ZT value are always dominated exclusively by one phase or the other and never by an average of both. For these compositions, the individual samples display properties vastly different from EMT predictions and can be exploited for an increased thermoelectric performance.
Highlights
Printable highly efficient thermoelectric materials[1,2] offer a promising approach towards low-cost thermoelectric generators (TEG).[3]
The need to use composite materials in printed thermoelectrics is usually accompanied by a significant reduction in the thermoelectric figure of merit if compared to the performance of the better of the two components
Calculating the effective thermoelectric properties of a composite material close to the percolation threshold by use of resistor networks (RRN) and expanded nodal analysis proved to be advantageous compared with the established GEMT
Summary
Printable highly efficient thermoelectric materials[1,2] offer a promising approach towards low-cost thermoelectric generators (TEG).[3] Such devices offer an elegant way to energy-harvest for autonomous sensor nodes, wearable electronics, and large-scale waste heat recovery.[4,5,6,7] TEGs operate by transforming thermal energy, usually from ambient or waste heat, directly into electrical energy This energy conversion is based on the Seebeck effect, which produces a voltage V = S × ΔΤ when a temperature difference ΔΤ is applied to the opposite sides of a thermoelectric material. The EMT[18,19] has been used to calculate the thermoelectric properties It approximates the complex network of different phases with an effective homogeneous material and calculates its resulting macroscopic properties based on the individual properties of the components and their volume fractions. We investigate the influence of percolation on the macroscopic ZT value and point out that the percolating phase with the higher conductivity dominates the charge transport and dictates the effective ZT value
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
