Preparation And Performance Optimization Of ?-MgAgSb Room-temperature Thermoelectric Materials

With people enter the new era,it also brings energy crisis and environmental problems.It has become the huge challenge to explore sources of abundance,cleaning and high-efficiency.Thermoelectric power generation can directly convert heat into electricity,also known as"temperature difference power generation".Thermoelectric device generates electricity utilizing electrons or holes of materials under directional motion driven by temperature difference.Thus,it has many advantages such as small size,no noise,and long life.The performance of thermoelectric device is largely determined by thermoelectric materials.There is currently only the Bi₂Te₃ material system in the low temperature field where the operating temperature is below 300?.However,its large-scale commercial application is limited because Te element is rare in the earth's crust which lead the expensive and costly,and poor mechanical properties of the materials lead the low yields.Recently,the thermoelectric material?-MgAgSb has abundant component element reserves and excellent thermoelectric performance,and is expected to replace Bi₂Te₃ and become a room temperature thermoelectric material for large-scale commercial applications.However,studies have shown that the traditional single-element doping is difficult to achieve the optimal carrier concentration,which limits its thermoelectric properties to further increase.Therefore,this review attempts to further improve its thermoelectric performance by increasing the power factor or reducing the thermal conductivity via double doping and nanocomposite.This work uses Yb-Ni co-doping to increase the carrier concentration of the sample and improve the power factor.In addition,lattice distortion effectively scatters low-and middle-frequency phonons,is caused by the large atomic mass and size of Yb,which effectively reduces the thermal conductivity and improves the thermoelectric figure of merit over the entire temperature range.In this work,the Li-Zn co-doping method is also used to increase the Seebeck coefficient by filtering the low-energy carriers with the performance band barrier.However,the Seebeck coefficient is sharply deteriorated after doping,and the resistivity is appropriately reduced.As a result,the thermoelectric performance has not been effectively improved.This article also attempts to optimize the thermoelectric properties of?-MgAgSb by introducing interfacial scattering with nanocomposites,increasing phonon scattering for different frequencies and reducing thermal conductivity.However,the result is that the thermal conductivity has significantly increase rather than decrease as expected.Both the resistivity and the Seebeck coefficient of the sample is significantly reduced for the composite,which ultimately result in comparable thermoelectric properties to the matrix.Furthermore,the mechanical properties deteriorate significantly and it is difficult to guarantee its long service life.In this review,the results show that double doping can only slightly increase carrier concentration and improve its thermoelectric performance.Other elements can also be double-doped to optimize the electrical transport properties of the material.How to form an energy band barrier to increase the Seebeck coefficient is still of research value.The use of nanocomposites has not optimized its thermal transport properties,and has also deteriorated the mechanical properties and made it easy to crack.