High-pressure Sintering And Properties Of Cu₂Se And Bi₂Te₃ Based Thermoelectric Materials

Cu₂Se and Bi₂Te₃ are thermoelectric materials with excellent performance.Due to the volatilization of Se and Te elements,it is difficult to form bulks through high temperature sintering.In this paper,the volatilization of Se and Te was inhibited by high H/N pressure sintering to prepare high-density bulks,and H and N atoms were infiltrated into the lattice structure of Cu₂Se and Bi₂Te₃-based thermoelectric materials,so as to reduce the thermal conductivity of the materials and finally increased its thermoelectric advantage?ZT?.The lattice structure and microstructure of the samples were characterized by XRD and SEM;The electrical and thermal properties of the samples were tested with the Seebeck coefficient meter and the flash thermal conductivity meter.The main conclusions are as follows:Sintered Bi₂Te₃ base materials with high H and N pressures:?1?Bi₂Te₃:After sintering in H₂ atmosphere with a pressure of 40 MPa,the conductive type of the sample changed from n to p,and the volume of the crystal cell increased by 4.25?³.When the test temperature rose to 100?,the conductive type changed from p to n,and the ZT value decreased with the increase of temperature,reaching a maximum value of 0.03 at room temperature.After sintering in N₂ atmosphere with a pressure of 40 MPa and 65 MPa,the conductive type of the sample did not change,and the ZT value decreased with the increase of temperature,taking 0.6 and 0.53respectively at room temperature.?2?Bi_0.5Sb_1.5Te₃:After high pressure sintering,Te element in Bi_0.5Sb_1.5Te₃ did not decompose,and the formed bulk was dense,reaching 85%of the theoretical density.The sample with the best performance was N₂ pressure of 65 MPa,and the volume of the crystal cell was 8.62?³ higher than that of the sample sintered at atmospheric pressure.At room temperature,its PF value was 2542?W/mK²,about 3 times of the sample sintered at atmospheric pressure,and its ZT value was 0.93,about 2 times of the sample sintered at atmospheric pressure.After sintering with H₂ pressure of 40 MPa,when the test temperature of the sample is 100?,ZT is 1.2.Sintered Sb₂Te₃ base materials with high H and N pressures:Under high pressure sintering,no element volatilization occurred in Sb2Te3,and the formed bulk was dense,reaching the theoretical density of 87%.Compared with samples sintered at atmospheric pressure,the surface pores of samples sintered at high pressure increase.At room temperature,PF reached the maximum value of 2298?W/mK²,which was 1.2 times higher than the sample sintered at atmospheric pressure.The thermal conductivity value was 1 W/mK,0.85 W/mK lower than the sample sintered at atmospheric pressure.The ZT value reached 0.68,2.2 times higher than the sample sintered at atmospheric pressure.Sintered Cu₂Se base materials with high H and N pressures:The samples of atmospheric pressure sintering are brittle and have volatilization and oxidation phenomena.Through sintering at high pressure,the oxidation and Se element volatilization in the compounds are inhibited,and the sintered bulk is densified.The bulk density can reach 98.7%of the theoretical density.At room temperature,the thermal conductivity value was 0.8 W/mK,and the ZT value could reach 0.25.