Production of Functional Materials for Advanced Thermoelectric Applications

Abstract

With ever increasing energy costs, climate change and energy supply concerns there has been a drive towards sustainable and renewable energy sources. There are many industries which currently produce excess waste heat such as reactors, motorised transport, metal production, and gas turbines to name a few. These industries can reduce their carbon footprint with successful heat scavenging. A much-overlooked technology is thermoelectric generators. These are solid-state devices which can convert heat directly into electricity using the Seebeck effect. There are number of advantages of thermoelectrics over conventional renewables including no moving parts, maintenance-free functionality in extreme environments, high-temperature resistance and long-life span. Thermoelectrics can function as both primary generators or as thermal scavengers, however they are not yet suitable for mass market applications. This thesis will investigate the entire thermoelectric device and develop scalable alternatives to current technologies. In this the production of earth abundant thermoelectrics, focusing on transition metal silicides, was investigated using a novel pack cementation technique to produce high quality materials that are affordable and require only low-cost equipment to produce. This technique was shown to produce high purity materials; however, production rates were limited due to the diffusion rates. The second part of this thesis investigated the soldered contacts for device construction; as current soldered contacts are subject to fatigue, can be costly and at times toxic. Molten liquid electrical contacts were developed and whilst promising are limited by their compatibility with current thermoelectric materials. The most successful work was that of printable, conductive polymers. These were developed to be stable at high temperatures, bind well with current thermoelectric materials and provide a new contact material allowing fully automated production. To ascertain the viability of the developed conductive polymer contacts, further work was undertaken to prototype functional devices which led to promising results for future upscaling.