The effect of interfaces in solids on the overall charge transport properties has become a topic of growing importance for energy materials such as thermoelectrics. In some polycrystalline thermoelectric materials, the performance near room temperature is significantly limited due to thermally-activated electrical conductivity near room-temperature, which can be attributed to grain boundaries. In this thesis, a combined experimental and theoretical approach is used to explore the grain-boundary effect on charge transport. A simple two-phase model is developed to explain the charge transport across grain boundaries in heavily-doped thermoelectric materials. The thesis will particularly focus on n-type Mg3Sb2 where the thermoelectric performance is improved by engineering the grain boundaries. The relevance to a broader range of materials is shown via re-examining literature data. The synthetic and measurement techniques for characterizing interfacial resistance is transferred to a study of contact resistance in Li-ion energy storage systems. With carefully design measurements the electrical resistance due to solid-solid contacts is shown to be important, especially under the scale relevant for applications.

Creator

• Kuo, Jimmy

DOI

• https://doi.org/10.21985/n2-v2zt-n908

Subject

• Physics
• Materials Science

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:15489
• etdadmin_upload_797891

Keyword

• Contact resistance
• Grain boundary
• Charge transport model
• Thermoelectric
• Mg3Sb2
• NMC

Date created

• 2021-01-01

Resource type

• Dissertation

Rights statement

• In Copyright