Development of TiCoSb-based Half-Heusler Materials for Thermoelectric Applications

This thesis investigates the enhancement of thermoelectric properties of Half-Heusler (HH) alloys, focusing on TiCoSb-based materials for mid-temperature waste heat recovery applications. It explores novel methods for designing high performance thermoelectric materials using advanced strategies. By optimizing both the electronic and thermal properties of HH alloys, the thesis contributes significantly to the development of high-performance thermoelectric materials for several energy generation utilizing waste heat. Chapter 1: Introduction & Literature Review This chapter introduces the fundamental concepts of thermoelectricity, including the principles of thermoelectric generators and coolers. It outlines the motivation behind using HH alloys, particularly TiCoSb-based materials, for thermoelectric applications due to their favorable properties such as high thermal stability and mechanical robustness. Chapter 2: Experimental Methods The second chapter includes the details of synthesis and characterization techniques used throughout the research. Synthesis methods include Arc Melting for initial material preparation followed by Spark Plasma Sintering to enhance the material's density and microstructure. Characterization techniques such as X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) are employed to analyse the phase composition and microstructure. Further, the electronic and thermal transport properties measurements systems are discussed. Chapter 3: Investigation of the appropriate sintering temperature for higher electronic transport and Mechanical Properties in TiCoSb In Chapter 3 we will Focus on the optimization of synthesis parameters to achieve high-quality thermoelectric materials. It examines the effects of different sintering temperatures and durations on the electronic transport properties of the materials, identifying optimal conditions that maximize performance. Chapter 4: Development of p-type TiCoSb-based thermoelectric materials This chapter addresses the development of p-type TiCoSb-based thermoelectric materials. It explores strategies such as band convergence and defect engineering to enhance the Seebeck coefficient and reduce thermal conductivity, thereby improving the overall ZT value. Chapter 5: Development of n-type TiCoSb-based thermoelectric materials Chapter 5 focuses on the development of n-type TiCoSb-based materials. It discusses the role of electron-phonon coupling and the impact of substituting different elements for Ti in the HH structure to enhance thermoelectric performance. Chapter 6: Fabrication of TiCoSb-based thermoelectric devices Describes the assembly of thermoelectric devices using the optimized TiCoSb-based materials. It includes the construction of both single-leg and multi-leg devices and evaluates their performance in converting waste heat into electricity. Chapter 7: Conclusion and Future Work Summarizes the research findings and discusses the implications for future work. Highlights the potential for HH alloys in commercial thermoelectric applications and suggests directions for further research to overcome current limitations.