Synthesis And Thermoelectric Properties Of Cu-Te?Ultra-fine Grain?/Cu₂SnSe₃ Composites

As a kind of energy material—thermoelectric material—it has demonstrated tremendous development potential and research value from all aspects.Its many advantages,such as environmental protection,convenience and long life,also demonstrate the development direction of new energy materials.Copper-based thermoelectric materials are attracting attention in the development of thermoelectric materials because of their unique thermoelectric properties and wide and economical raw materials.In this dissertation,Cu₂SnSe₃ matrix was prepared by vacuum melting method,and Cu-Te alloy ribbon was prepared by melt spinning method?MS?,and the microstructures of Cu-Te alloy obtained by spin-off at different cooling rates were studied.The two kinds of powders were mixed by ball milling and sintered into Cu-Te/Cu₂SnSe₃ thermoelectric composites by spark plasma sintering?SPS?.Finally,the prepared composites were analyzed in terms of phase,microstructure and tests of thermoelectric properties.The effects of Cu-Te alloys prepared on at different speed of rotating copper roller the microstructure and thermoelectric properties of Cu₂SnSe₃ matrix and different additions were compared.The Cu-Te alloy ribbons were prepared by melt spinning method at the speeds of 20 m/s,25 m/s,and 30 m/s respectively.All ribbons obtained are uniform and have fine grains.The size of the contact surface is about several hundred nanometers,and with the rotation speed of copper roller increasing,the grain is further reduced.Through the analysis of sectional SEM view,we can see the finely distributed layered structure.XRD examination revealed that the Cu-Te alloy after melt spinning contains the following phases:Cu₂Te,Cu_2-xTe,Cu_3-xTe,CuTe,and Cu₄Te₃.The phase of Cu-Te alloy is well distributed inside the Cu₂SnSe₃ matrix and no new phase is formed.According to SEM and EDS analysis,Cu-Te phases are mainly distributed in the grain boundary of Cu₂SnSe₃ matrix.Cu-Te phase has the effect of hindering Cu₂SnSe₃grain growth during the sintering process.The grain size of Cu-Te-25/Cu₂SnSe₃ and Cu-Te-30/Cu₂SnSe₃ composites gradually decreased,with the addition of Cu-Te increaseing.When the addition amount of Cu-Te is at a higher level?0.8 vol.%and 1.2 vol.%?,the void content of the composite increases as the Cu-Te size decreases.The lattice thermal conductivity and total thermal conductivity of Cu-Te-20/Cu₂SnSe₃composites are greatly reduced,and when the Cu-Te content is 0.8 vol.%,the ZT of the composite has a maximum value of 0.45 at 700K,which is 87.5%higher than that of matrix phase.The Cu-Te-25/Cu₂SnSe₃ composites have good electrical properties,and when the Cu-Te addition amount is 0.8 vol.%,the maximum ZT value is 0.27 at 700K.The Cu-Te-30/Cu₂SnSe₃ composite has a high Seebeck coefficient,and when the Cu-Te addition amount is 1.2vol.%,the composite has a maximum ZT of 0.31 at 700K.When Cu-Te is added in an amount of 0.4 vol.%,the power factor of Cu-Te-25/Cu₂SnSe₃composites is at the highest level,but at 700 K,the Cu-Te-20/Cu₂SnSe₃ composite has the lowest thermal conductivity and the maximum ZT value.When the addition amount of Cu-Te is 0.8 vol.%,the Cu-Te-20/Cu₂SnSe₃ composite has the highest PF,the lowest thermal conductivity and the largest ZT value.When Cu-Te is added in an amount of 1.2 vol.%,the Cu-Te-30/Cu₂SnSe₃ composite has the highest PF,and the Cu-Te-20/Cu₂SnSe₃ composite has the lowest thermal conductivity and maximum ZT.Comparing Cu-Te-25/Cu₂SnSe₃ with Cu-Te-30/Cu₂SnSe₃ composites,it can be found that as the Cu-Te grain size decreases,the electrical conductivity and lattice thermal conductivity of Cu-Te/Cu₂SnSe₃ composites decreases,while the Seebeck coefficient of composites increases.