Executive Summary : | To fabricate the thermoelectric devices, whose efficiency will improve and convert the waste heat into electricity and can be used to utilize the waste heat released from hot combustion engines to the atmosphere, heat produced from industrial sources, the heat released from the surfaces of hot equipment and heat released from the heated water of a nuclear power plant. To fabricate these thermoelectric devices, it is required to investigate some high TE figure of merit materials, which can be incorporated into the devices to have maximum efficiency. Out of available state of art thermoelectric materials, we are choosing Bismuth Telluride(Bi_2 Te_3) for low-temperature (~300 K) application, Lead Telluride(PbTe) for mid-temperature (400-800 K) application, Skutterudite(CoSb_3) for mid-temperature (300-900 K), and Copper Selenide (Cu_2 Se) for mid-temperature (500-850 K) due to their high figure of merit zT and stability at the given temperature range. After selecting the TE materials, we will start doing synthesis of these materials. To synthesize TE materials, we will follow solid state synthesis route. Then, we will start characterizing these materials by performing some characterization experiment like X-Ray diffraction (to know about the phases present inside the sample), Electron probe micro analysis (to know about the composition of those phases present inside the sample), Thermal analysis using TGA and DSC (to know about the thermal decomposition and phase transition behavior of the sample). After synthesizing the selected TE elements, we will investigate the required contact electrode, and to stop the diffusion between contact electrode and TE element at high temperature. PIs are proposing some intermediate material which can stop the diffusion and can be act as a diffusion barrier for both the contact electrode and TE element. Then, the coefficient of thermal expansion (CTE) will be measured for individual sample to confirm the suitability of each material. Then to join the electrode and TE element together with the intermediate material, investigate some bonding techniques available in the literature and investigate some new techniques which has not been studied so far. The metal-semiconductor contact physics properties will be explored. Then to test the thermal stability of thermoelectric joints, thermal ageing cycles will be performed for different annealing temperatures and subsequently Electron Probe Micro Analysis will be performed to closely monitor the joints. After testing the stability of TE joints, contact resistance will be measured at high temperature under vacuum using the proposed experimental setup and contact resistance will be plotted as a function of probe distance. Finally, after experimentally calculating zT value for all samples, performing thermal ageing tests, and calculating contact resistance, high performance TE materials will be fabricated into devices and their efficiency will be calculated. |