Controllable Synthesis And Properties Study Of Stannous Sulfide Thermoelectric Materials

With more than two-thirds of worldwide utilized energy being wasted as heat releasing to atmosphere in vain,it is of great economic and environmental benefit to capture this largely untapped waste heat to generate emission-free renewable power.Thermoelectric material is a kind of new clean functional material that uses temperature gradient to generate electrical energy.In today's society where energy problems are increasingly serious,it is of great significance to increase the conversion efficiency of thermoelectric materials and accelerate the commercialization of thermoelectric materials through research.As a synthetic method with simple process,low cost and good powder properties,chemical precipitation has attracted widespread attention in the field of materials science.For the first time,SnS bulk thermoelectric material was synthesized and prepared by chemical precipitation combined with rapid hot-pressing sintering.The effects of different annealing temperatures on the morphology and thermoelectric properties of the bulk samples were investigated.At the same time,the anisotropy of SnS bulk samples was initially explored.For the 923 K annealed samples,the ZT value was 0.41 parallel to the hot-pressing direction,and the thermal conductivity reached a very low value of 0.29 W/(m*K)at 848 K.In addition,the experimental results show that three different annealing temperature samples of three different micro-morphologies are obtained.The analysis shows that the thermoelectric properties of SnS can be adjusted by changing the micro-morphology of the bulk sample.This work provides a new and simple method to obtain SnS with high ZT value,which will provide new ideas for finding new thermoelectric materials.The thermoelectric properties of stannous sulfide can be further improved by reasonable doping on the basis of this work.The mechanical alloying method is one of the effective methods for doping of materials which has a wide range of applications in the field of thermoelectric materials.Because of the chemical precipitation method can not do the precise and effective doping of the material,in order to further improve the thermoelectric properties of SnS,this paper adopts the mechanical alloy method to try different elements of SnS doping.For samples with 2% Li doping,doping can effectively increase the carrier concentration and the electrical conductivity of Sn S.It was found that doping increases the internal defect level of the sample and effectively reduces its thermal conductivity.The ZT value reaches 0.66 at 848 K,which is more than twice the ZT value of the pure phase SnS synthesized in this paper and is more than three times that of the pure phase SnS in the literature.Therefore,the doping of Li is a very effective method to improve thermoelectric properties of SnS.Simultaneously,single element doping of Ni doping and double elemental doping of I and Cu were performed on SnS.It was found that these dopings can effectively reduce the thermal conductivity of SnS..The lowest thermal conductivity of samples which doping amount is 1% Ni can reach 0.23W/(m*K)at 848 K,and the thermal conductivity is reduced by about 50% at the same temperature point than that of pure phase SnS.This is the lowest thermal conductivity of SnS in this paper.In the end,experiments were conducted on the carbon nanotubes composite experiment of SnS.The composite carbon nanotubes can increase the electrical conductivity of stannous sulfide to a certain extent,and at the same time can effectively reduce its thermal conductivity,but it cannot improve the thermoelectric properties of SnS from the whole.