Influence Of Cold Pressing Sintering Process Parameters On Thermoelectric Properties Of Cu₂S Based Ceramics

As a new type of clean energy,thermoelectric materials can directly convert heat energy into electric energy through the movement of internal carriers.Moreover,the material itself has the advantages of good stability and simple structure,which has become the research hotspot of new energy materials.Thermoelectric materials have great potential in waste heat recovery,refrigeration and other fields,and are expected to make an important contribution to slow down the speed of environmental pollution and supplement the inefficient use of traditional energy materials.Thermoelectric materials have great potential in the fields of waste heat recovery and cooling,which can play an important role in slowing down the speed of environmental pollution and supplementing the low efficiency of traditional energy materials.Among them,sulfide thermoelectric materials have the advantages of low cost,small toxicity,large reserves and so on.Its future commercial application potential is huge,which has been widely studied by many researchers.Cu2-xS,as a typical sulfide system,can be divided into copper poor and copper rich Cu2S,which have a series of copper deficient compounds.However,the performance of the ceramic devices made of copper sulfide based thermoelectric materials in the middle temperature region is still low,which needs to further improve the thermoelectric conversion efficiency.which requires further improvement of thermoelectric conversion efficiency.The sintering process of ceramics is usually the key factor to determine the performance of devices.For many years,people have been looking for ways to reduce sintering temperature.The realization of low temperature sintering can not only save the energy loss in the sintering process,but also break through many research limitations.In recent years,a new sintering process,low temperature cold pressing sintering process,has been widely concerned.It has successfully achieved densification of various ceramics at very low temperature(room temperature-300?),which is a very potential sintering process.Taking Cu2S as the research object,this paper aims to select the optimal low temperature cold pressing sintering process for preparing Cu2S bulk thermoelectric materials by comparison and selective research.Based on the research status available at home and abroad,this paper focuses on the experimental process of Cu2S powder preparation to sintering out of block,using the method of single variable exploration under the same conditions,respectively studied the thermoelectric properties of samples prepared under the conditions of adding different content of sintering aids,applying different sintering pressure,setting different sintering temperature and setting different sintering time.The main work is as follows:1.The Cu2S powder was prepared by thermal decomposition method.The chemical precipitation method was used to prepare the Cu2S powder in the tubular furnace with different temperature parameters(900?,1000?,1100?),and its composition was analyzed by XRD.The experimental results show that different thermal decomposition temperature has great influence on the product,and the pure Cu2S powder is obtained at 1000?.2.Adjust the parameters of the amount of additives(0 wt%,5 wt%,10 wt%,15 wt%)in the process of cold pressing sintering,and test the thermoelectric properties of the sintered ceramic samples.The experimental results show that all samples are densified in different amount of combustion aids,and different amount of combustion aids have corresponding effects on the thermoelectric properties of Cu2S ceramic samples,among which the sample prepared with 5wt%of combustion aids has the best performance,and the ZT value reaches 1.38 at 823K.3.Control the parameters of pressure applied in the cold pressing sintering process of thermal decomposition CU2S powder[400MPa(70.8KN),450MPa(79.6KN),500MPa(88.4KN),550MPa(97.4KN),600MPa(106.2KN)],and test the thermoelectric properties of the sintered ceramic samples.The experimental results show that all samples are densified under different sintering pressure,and the different sintering pressure has a corresponding impact on the thermoelectric properties of Cu2S ceramic samples,among which the sample prepared under 500 MPa pressure has the best performance,reaching the maximum ZT value of 0.97 at 823K.4.Adjust the parameters of sintering temperature(150?,200?,250?,300?,350?)during the cold pressing sintering process of thermal decomposition Cu2S powder,and test the thermoelectric properties of the sintered ceramic samples.The experimental results show that under different sintering temperature parameters,all the samples have achieved densification,and different sintering temperature parameters have a corresponding impact on the thermoelectric properties of Cu2S ceramic samples.Among them,the samples sintered at 300? have the best performance,reaching the maximum ZT value of 0.33 at 823K.5.Adjust the sintering holding time parameters(set as 30min,60min,90min and 120min respectively)during the cold pressing sintering process of the thermal decomposition Cu2S powder,and test the thermoelectric properties of the sintered ceramic samples.The experimental results show that under different sintering holding time parameters,all samples have achieved densification,and different sintering holding time parameters have a corresponding impact on the thermal and electrical properties of Cu2S ceramic samples,of which the sintering performance under 90 min sintering holding time parameters is the best,reaching the maximum ZT value of 2.38 at 823K.