Study On Improving Thermoelectric Properties Of Bi₂Te₃ Semiconductor Based On Electroless Plating And Annealing Treatment

Since human beings entered industrial civilization,fossil energy as the driving force of human civilization has become more and more perfect,but its disadvantages have become more and more acute,environmental pollution and its non-reproducibility urge researchers to find a new type of clean energy.Environmental pollution and its non-renewable nature urge researchers to search for new clean energy.Thermoelectric materials,as a kind of functional materials which convert heat energy and electric energy into each other,are widely concerned.They can generate electricity by using the thermal difference of the materials themselves,and can also connect the current to realize the refrigeration at one end of the material,which has a wide range of applications.At present,Bi-Te based thermoelectric materials are the most mature thermoelectric materials in the vicinity of room temperature.However,with the continuous exploration of thermoelectric materials by researchers in recent years,a large number of thermoelectric materials of new systems have been developed.Bi₂Te₃-based thermoelectric materials are much less excellent than their thermoelectric values.Therefore,in view of the low conversion efficiency of Bi₂Te₃-based thermoelectric materials,we use electroless plating and annealing to improve its thermoelectric value and explore its influence on thermoelectric and mechanical properties.The specific elements and outcomes are as follows:1.The effect of electroless copper plating and annealing on P type Bi_0.5Sb_1.5Te₃alloy was investigated.Electroless copper plating greatly enhanced its conductivity and increased its ZT value.At the same time,grain refinement after annealing resulted in more phonon scattering at grain boundaries,which reduced the lattice thermal conductivity and increased its ZT value.For thermoelectric excellent value ZT,The annealed sample is higher than the unannealed sample,and the electroless copper plating sample is higher than that of the unannealed sample.Finally,the highest ZT value and average ZT value of the sample treated by electroless copper plating and annealing are 0.71 and 0.65 respectively.2.On this basis,the effect of composite electroless nickel and copper plating on P type Bi_0.5Sb_1.5Te₃alloy was further studied.Double heavy metal doping increases carrier concentration,carrier mobility and effective mass,and increases the power factor of the material.At the same time,the double metal doping forms various scale defects in the material,and reduces the lattice thermal conductivity.Finally,the highest ZT value of1.16 was obtained in the 0.3wt.%Ni0.25wt.%Cu sample.3.For N-type Bi₂Te₃based thermoelectric materials,the effect of electroless copper plating on Bi₂Te_2.4Se_0.6alloy was investigated.Unlike P-type thermoelectric materials,electroless plating mainly increases the Seebeck coefficient,but decreases the conductivity.Finally,the highest ZT value of the sample with concentration of0.05wt.%Cu was 0.94,which was 44.6 higher than that of the original Bi₂Te_2.4Se_0.6alloy.4.Based on the above experimental results,we have carried out a preliminary study on the treatment of Bi₂Te_2.4Se_0.6alloy by chemical galvanizing and tin plating.The experimental results show that Electroless galvanizing can greatly increase the ZT value when the composition concentration is low.In the experimental results,the ZT value of the first batch of concentration of 0.15wt.%is the highest,when the concentration of the component increases to 0.35wt.%,the ZT value of the first batch is the highest,when the concentration of the component increases to 0.35wt.%,The ZT value of the sample is not significantly different from that of the original Bi₂Te_2.4Se_0.6sample.Finally,the maximum ZT value of the sample is 1.06,which is 53.6%higher than that of the original sample,while the ZT value of Bi₂Te_2.4Se_0.6alloy is decreased by chemical tin plating process,which is even lower than that of the original Bi₂Te_2.4Se_0.6sample.