Study On Thermoelectric Properties Of Cu_2-xS Prepared By Cold Sintering Process

Excessive fossil energy use and low energy efficiency have forced us to look for new technologies and new materials to improve this situation.Thermoelectric materials and thermoelectric energy conversion technology have attracted extensive attention of researchers in recent decades because they can realize the conversion between thermal energy and electric energy,which does not require any transmission devices and is an environmentally friendly energy technology.The P-type Cu2S compound has the advantages of abundant earth reserves and environmental friendliness,and has good thermoelectric properties.It is a thermoelectric material with potential electronic crystal-phonon glass characteristics.The sintering process of ceramics is often the key factor to determine its performance.For many years,people have been looking for ways to reduce the sintering temperature.Low temperature sintering can not only save energy consumption in the sintering process,but also break through many research limitations.Recently,a new sintering process,cold sintering process(CSP),has attracted wide attention.It has successfully realized the densification of various ceramics at very low temperatures(room temperature-300?),which is a very promising sintering process.In this paper,the copper precursor is used as the matrix,the ceramic precursor powder is prepared by thermal decomposition method and mechanical alloying method,and the cuprous sulfide thermoelectric ceramic is prepared by cold sintering process.The specific contents include the following aspects:1.Cu2S powders were prepared by thermal decomposition method.Ceramics were sintered at different temperatures(room temperature,50?,100 ?,150?)by CSP and their thermoelectric properties were tested.The experimental results show that the ceramic densification is achieved by the CSP at different sintering temperatures.Changing the sintering temperature has a certain impact on the thermoelectric properties of the Cu2S ceramics.The sample sintered at 150 ? has the best thermoelectric properties,and the ZT value reaches a maximum of 0.86 at 823K.2.Cu2-xS(0?x?0.2)powder was prepared by mechanical alloying method.Cu2-xS thermoelectric ceramics were prepared by CSP.The effect of Cu ion vacancy content on the thermoelectric properties of Cu2S was investigated.The experimental results show that different copper deficiency ratios have a great influence on the properties of Cu2S thermoelectric ceramics.The samples with higher copper deficiency ratios have better conductivity,but at the same time,the thermal conductivity increases.In this paper,the ZT of sample x=0.1 reaches 1.27 at 823K.3.Cu2S1-xSex(x=0,0.5,1)powders were prepared by mechanical alloying method.Cu2S1-xSex thermoelectric ceramics were prepared by CSP process.The effects of excessive doping of Se(S)on the thermoelectric properties of Cu2S(Cu2Se)were investigated.The experimental results show that the excessive doping of Se element has a significant effect on the conductivity of Cu2S,but at the same time affects the thermal conductivity,which ultimately leads to a decrease in thermoelectric performance.Excessive doping of S element does not improve the thermoelectric properties of Cu2Se.In all samples,the ZT value of sample x=1 reached a maximum of 1.26 at 823K.