Composite And Doping Regulation Of Cu_1.8S Based Thermoelectric Materials And Their Thermoelectric Properties

Increasing energy demand and decreasing traditional energy reserves,as well as the world's concerns about climate change caused by global warming.The need for energy and the concern for the environment make us urgently need new energy sources.Thermoelectric materials,as a new type of energy materials,are environmentally friendly,recyclable,large reserves and other advantages,which can significantly improve the utilization rate of energy.Cu-based chalcogenides are widely concerned as a thermoelectric material,among which Cu and S have large reserves,low price and low toxicity.Therefore,Cu_1.8S was adopted as the research object in this study,and its thermoelectric properties were regulated by means of composite and doping.In this experiment,the precursor powder was prepared by mechanical alloying method,and the sintering method was low temperature Cold Sintering Process.The effects on the thermoelectric properties of Cu_1.8S were studied by combining different contents of CNTs,graphene,a mixture of CNTs and graphene,and doping different contents of Ag.The content of this paper includes the following four aspects:1.Cu_1.8S powders were prepared by mechanical alloying method,and CNTs in different proportions were compounded with the composite amounts of 0.25wt.%,0.5wt.%and 1wt.%,respectively.The influence of composite CNTs on the thermoelectric properties of Cu_1.8S material was explored.The results showed that the composite of CNTs would reduce the conductivity of Cu_1.8S but increase its Seebeck coefficient,thus improving its power factor as a whole.Moreover,the thermal conductivity decreased due to the cavity caused by CNTs.Compared with pure Cu_1.8S,the ZT value increased by 77%and 33%at 0.25wt.%and 0.5wt.%.2.Cu_1.8S powders were prepared by mechanical alloying method,and graphene was composite in different proportions,with composite amounts of 0.25wt.%,0.5wt.%and 1wt.%,respectively.Although graphene and CNTs are the same element,due to the particularity of graphene structure,the influence of its special structure on the thermoelectric properties of Cu_1.8S material was explored.The experimental results show that the conductivity of Cu_1.8S decreases after the composite graphene,while the Seebeck coefficient increases,but the power factor of all the samples after the composite graphene is lower than that of pure Cu_1.8S.3.A mixture of Cu_1.8S powder,composite CNTs and graphene was prepared by mechanical alloying method,in which the molar ratio of CNTs and graphene was 1:1,and the composite content was 0.25wt.%,0.5wt.%and 1wt.%,respectively.The effects of CNTs and graphene mixtures on the thermoelectric properties of Cu_1.8S were investigated.The results show that the power factor of the mixture is higher than that of pure Cu_1.8S at 373K?673K when the compound amount is 0.25wt.%.4.Cu_1.8-xAg_xs(x=0.005,0.01,0.015,0.02)powders were prepared by mechanical alloying method,and the bulk materials were prepared by Cold Sintering Precess at low temperature.The effects of Ag doping on the thermoelectric properties of Cu_1.8S materials were studied by doping Ag.The results show that the doping of Ag can improve the conductivity and Seebeck coefficient of Cu_1.8S material,and the power factor of all the Ag doped samples from 373K to 673K is higher than that of pure Cu_1.8S.