Microwave Synthesis And Thermoelectric Properties Of Sb Doping Half-Heusler Alloys

The rapid development of modern industry makes the consumption of fossil energy continues to increase,while a large number of industrial waste heat,energy crisis and environmental degradation has become increasingly prominent.Thermoelectric materials through the interaction of internal carriers and phonons to achieve thermal energy and energy conversion between each other,can be natural temperature,industrial waste heat and other low-grade energy directly into electrical energy,and actively carry out research on thermoelectric materials to deal with energy and Environmental crisis is of great significance.Half-Heusler alloy is a promising medium and high temperature thermoelectric material,in which MNi Sn?M = Hf,Zr,Ti?based alloy due to the abundance of various elements,non-toxic advantages,The focus of research on the thermoelectric materials of half-Hessler thermoelectric alloy block preparation using solidphase reaction method,arc melting method and powder metallurgy method,supplemented by hot pressing technology or discharge plasma technology to prepare dense block.The process often results in coarse grain and uneven composition,which requires a long period of annealing to refine the grains,resulting in a complicated process and costly preparation.Because microwave heating has the characteristics of dielectric heating,rapid heating and body heating and inverse temperature gradient,it has been widely recognized and widely used in the synthesis of materials.In this paper,microwave heating is proposed to rapidly prepare half-Hessler thermoelectric block,and its microstructure and thermoelectric properties are studied.The main results are as follows:?1?The effect of Sb at different Sn sites on the thermoelectric properties of TiNiSn was investigated.The results show that the conductivity of TiNiSb0.03Sn0.97 and TiNiSb_0.04Sn_0.96 is reduced by 84% compared with that of undoped TiNiSn alloy.The maximum power factor of TiNiSb0.03Sn0.97 sample at 573 K is 2560?Wm-1K-2,which is 113% higher than that of non-doped TiNiSn.The use of microwave heating can make the sample produce nano-precipitates and nano-pores,can increase the phonon scattering,reduce lattice thermal conductivity.However,the total thermal conductivity of the samples TiNiSb0.03Sn0.97 and TiNiSb_0.04Sn_0.96 is 3.8 to 4.0 Wm-1K-1 because the dopant of Sb increases the carrier concentration of the material and increases the thermal conductivity of the material,An increase of about 50% compared to non-doped TiNiSn.It can be seen that the doping of Sb improves the electrical properties of TiNiSn but also increases its resistivity.However,considering the ZT value of the material,the ZT value of TiNiSb0.03Sn0.97 is 0.44 at 673 K,Which is 46.7% higher than that of non-doped and similarly doped TiNiSn blocks.?2?The effect of partial Ti substitution on the thermoelectric properties of TiNiSn was studied by using Hf.The results show that the resistivity decreases with the increase of Hf content,and the resistivity decreases by 78% relative to the non-doped TiNiSn block.The Seeebck coefficient also increases with increasing Hf content.Maximum Hf0.1Ti0.9Ni Sn_0.97Sb_0.03 The sample has the largest Seebeck coefficient at 723 K of 120 uvk-1.Hf0.1Ti0.9Ni Sn_0.97Sb_0.03 sample has the largest power factor,278wm-1k-2 at 723 k compared to the sample TiNiSb0.03Sn0.97 increased by 7% compared to the non-doped TiNiSn alloy Said improved by 129%.The use of microwave heating can make the sample produce nano-precipitates and nano-pores,can increase the phonon scattering,reduce lattice thermal conductivity.However,the Sb element doping on the one hand increases the electrical carrier concentration and increases the thermal conductivity of the electrons.Hf0.2Ti0.8 Ni Sn_0.97Sb_0.03 samples have the lowest thermal conductivity in this series at 2.6 Wm-1K-1.In combination,the ZT of the Hf0.1Ti0.9Ni Sn_0.97Sb_0.03 sample is preferably 0.46 at 723 K,which is 50% higher than that of the non-doped TiNiSn.For TiNiSn_0.97Sb_0.03 promotion is not obvious,which may be due to microwave sintering process generated Hf O2,Ti Ni2 Sn impurities and Sb elements to increase the carrier concentration of the material Seebeck coefficient of a certain limit caused.The half-Heusler alloy block can be prepared quickly by microwave synthesis process,the preparation cycle is shortened and the material performance is relatively good.With the development of microwave technology,microwave technology will be applied in more areas.The development of this paper has important scientific value and academic significance to promote the application of microwave in the field of thermoelectric materials.