Research On Preparation Technologies And Properties Of Half-heusler Thermoelectric Materials And Modules

Half-Heusler thermoelectric materials are a research hotspot in the recent two decades and they show great potential to use commercially due to their high service temperature,great thermoelectric performance,relative low price,excellent mechanical properties and good thermal stability.And until now,the researches about batch synthesis technique,barrier layer and module design of this kind of modules are rare.Thus,the modules just can reach about 60%properties of their calculation value based on the materials properties.In this article,developing high performances half-Heulser modules are taken as the target.So we explore the whole chain about relative applied science including batch synthesis half-Heusler thermoelectric materials,structure design and integration,and the barrier layer design.The main innovative points in this dissertation are as following:1.The first principle method combined with experiments are applied to study thermodynamics of SHS prepared tenary half-Heusler compounds.The results show that SHS reactions of half-Heusler compounds are stepwise,the second step provide the major energy.The SHS method is adopted to prepared half-Heusler materials hunders grams per ingot and their z Ts are similar with these prepared by LM method.2.The Cr and Mo are developed as the barrier layer for Zr Ni Sn based and Zr Co Sb based half-Heusler materials due to the modules'interfaces become unstable and deteriorate at high temperature and limit the modules service temperature.The fine microstructure,reaction enthalpy calculation,contact resistance interfaces between Cr,Mo and Zr Ni Sn,Zr Co Sb based half-Heusler materials are studied.The results the interfaces are stable and obtain relative high electrical property.3.The structures of single-stage and two-stage segmented modules are designed and optimized based on batch prepared half-Heusler materials.The structure is designed and optimized.Thus,the maximum experimental conversion efficiency of half-Heusler single-stage and segmented modules attain record high value 11.1%and 13.3%,respectively.4.The design method,matched properties,structure design,integration and measurement of modules with high power density and high conversion efficiency are proposed.We develop“thermal match”materials n-type Zr_0.5Hf_0.5Ni Sn_0.97Sb_0.03and p-type Nb_0.86Hf_0.14Fe Sb according to the criteria.The module structure is design and optimized by the finite element simulation model and the effect of contact resistance is also taken into consideration.The measured maximum conversion efficiency is 10.5%and maximum power density is 3.1 Wcm^-2 at temperature difference of 680 K.The maximum power density and conversion of this module are both record value among similar thermoelectric generator modules.