Advanced Characterization of Thermoelectric Materials using Micro Four-Point Probe

Research output: Book/ReportPh.D. thesis

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Abstract

Rising global temperature due to the emission of greenhouse gases into the atmosphere causes climate changes worldwide. Addressing this critical issue requires action, sustainable and cost-friendly resources. Discovering and implementing renewable energy sources is a progressive topic of research that requires more attention for their potential usage on a large scale. Some of the most accepted/investigated renewable resources are biomass, wind, solar, hydropower, and thermoelectric.
Thermoelectrics are an emerging part of the solution to mitigate the effects of global warming. Thermoelectrics convert heat into electricity and vice versa; consequently, they can be used for waste heat recovery, refrigeration, space missions, automobiles, and the Internet of Things (IoT). Characterization of thermoelectric material is challenging as it requires multiple tools. To continuously improve the efficiency of these materials, it is crucial to characterize their properties with high accuracy and speed. The main objective of this project has been to develop a new micro four-point probe (M4PP) based metrology method suitable for characterizing thermoelectric materials.
This thesis proposes a faster, calibration-free, non-destructive method for advanced characterization of the Seebeck coefficient, thermal and electrical conductivity based on M4PP. Here, a method that combines three four-point probe measurements, named the triplet method, was developed. This method reduces the complexity of measurements from two heaters to a single heater, resulting in simplified temperature models during M4PP measurements. Later, it is used to verify temperature models down to 1 μm length scale on high thermal diffusivity doped Si samples. The triplet method was further developed for calibration-free extraction of microscale isotropic and anisotropic thermal diffusivity for individual grains of material. The concept was verified on two of the most studied thermoelectric materials, Bi2Te3 and Sb2Te3, with < 5% precision. This new method using M4PP holds promising potential for future thermoelectric/materials characterization and a complex understanding of grain boundaries and their effect on thermal properties.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages150
Publication statusPublished - 2023

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