Study On The Effect Of Doping Of Main Group Ⅲ Elements On The Thermoelectric Properties Of Polycrystalline SnSe Synthesized By Hydrothermal Method

Thermoelectric materials have the characteristics of direct conversion between electrical energy and thermal energy,which provide effective solutions to the current increasingly severe energy problems.Among the SnSe materials that are non-toxic,environmentally friendly and have excellent economic benefits,single crystal SnSe has better thermoelectric properties,but it is difficult to be applied in practice due to the complicated single crystal preparation process and poor mechanical properties.Therefore,for large-scale practical applications,polycrystalline SnSe,which is simple to prepare,easy to synthesize in large quantities,and has good mechanical properties,has become the research focus of thermoelectric researchers.Researchers use heteroatom doping and control the degree of texture,introduce nano heterogeneous phases,point defects and nano pores and other methods to improve the thermoelectric properties of polycrystalline SnSe.In this paper,two strategies of magnetic field-assisted hydrothermal synthesis of Ga doping and Ge and In co-doping are used to improve the thermoelectric performance of polycrystalline SnSe,and obtain a polycrystalline SnSe thermoelectric material with a higher thermoelectric figure of merit.The core research results of this paper are as follows:1.Prepare Ga-doped polycrystalline SnSe samples by means of strong magnetic field assisted hydrothermal method and spark plasma sintering.The magnetic field environment regulates the growth of crystals.Since the magnetic field can provide additional energy without directly contacting the solution,the Ga-doped samples prepared under the magnetic field have smaller grains.The electrical performance test found that the magnetic field will increase the carrier concentration and increase the conductivity.At the same time,due to the increase in the density of states,the Seebeck coefficient of the magnetic field is higher than that of the Ga-doped samples prepared without the magnetic field,so the power factor of the samples prepared by the magnetic field is higher.In addition,The 5T magnetic field environment affects the grains and thus enhances phonon scattering,leading to a decrease in lattice thermal conductivity,which in turn reduces the total thermal conductivity.The strong magnetic field assisted hydrothermal synthesis of Ga-doped polycrystalline SnSe has achieved a thermoelectric figure of merit of 2.02 at 873K by synergistically optimizing the electrical and thermal properties.2.Ge and In co-doped polycrystalline SnSe samples were prepared by hydrothermal synthesis of powder at room temperature and rapid high-temperature discharge plasma SPS sintering.Ge and In doping will introduce holes,and because the polycrystalline SnSe is a p-type semiconductor,the carrier concentration is greatly increased and higher conductivity is obtained.At the same time,the Seebeck coefficient decreases to a small degree,so a higher power factor of 5.8μWcm^-1K^-2is obtained.In addition,Ge and In doping leads to the generation of point defects and enhanced phonon scattering,resulting in lower lattice thermal conductivity.Since the lattice thermal conductivity of SnSe is dominant,the total thermal conductivity It has also been greatly reduced.The higher power factor and the reduced total thermal conductivity have a synergistic effect to achieve a peak thermal power figure of 1.9.