Preparation And Properties Of Cu₂SnS₃ Thermoelectric Materials

With the progress of the times,environmental pollution,climate warming,energy crisis,and other issues have become increasingly prominent.In order to get out of this dilemma,people have been struggling to find a solution to the problem.In this process,thermoelectric materials with its unique advantages have attracted much attention.Thermoelectric materials can achieve a direct conversion of thermal energy and electric energy without any emissions and are environmentally friendly.At present,the thermoelectric materials used in the market,such as bismuth telluride,are so rare in the earth's crust that makes the cost of thermoelectric materials is very high.It is very necessary to find low-cost thermoelectric materials.Cu₂SnS₃,as a thermoelectric material,has gradually entered the vision of researchers.Its constituent elements are very common,and the characteristic of"phonon glass-electronic crystal"with low thermal conductivity makes it a potential thermoelectric material.However,the electrical properties of intrinsic Cu₂SnS₃ are low must-be improved by doping.In this paper,solvothermal synthesis and microwave sintering were used to prepare Cu₂SnS₃ thermoelectric materials and the following studies were performed:(1)The Cu₂SnS₃ powders were synthesized by solvothermal methods with different solvents.The ethylenediamine and water were selected as the solvents by studying the morphology of the synthesized powder and electrical properties after sintering.The average particle size of the synthesized powder is 50 nm and its distribution is uniform.(2)After cold isostatic pressing,the synthesized Cu₂SnS₃powder was microwave sintered and the effect of sintering temperature on the thermoelectric properties was studied.(3)As the acceptor dopant,the ion radius of Co²⁺(74.5 pm)is similar to that of Sn⁴⁺(69 pm),the substitution of Co²⁺for Sn⁴⁺can increase the carrier concentration and the electrical conductivity.At the same time,the substitution produces lattice defects and scatters phonon,thus enhances the thermoelectric performance.The ZT value of Cu₂Sn_0.8Co_0.2S₃ is 0.77 at 700 K.(4)Fe³⁺as the acceptor dopant,not only the ion radius of Fe³⁺(64.5 pm)is close to that of Sn⁴⁺(69 pm)but also the valence of them is similar,and the acceptor is more easily ionized to improve the electric transport performance.The electrical conductivity of Cu₂Sn_0.95Fe_0.05S₃ is the highest at room temperature,reaching 3597.05Scm^-1.At the same time,solvothermal synthesis and microwave sintering restrict the growth of grains,which results in low thermal conductivity of the sintered sample.The ZT value of Cu₂Sn_0.85Fe_0.15S₃ reaches 1.2 at 700 K.