Microwave Synthesis And Enhancement Of Thermoelectric Performances For TiNiSn Half-heusler

With the acceleration of industrialization,human consumption of energy is also increasing.Due to the extensive development and utilization of non renewable energy,energy supply is short and environmental pollution is becoming more and more serious.Thermoelectric material is a kind of green functional material which uses carrier motion,Seebeck effect and Peltier effect inside the material to realize energy conversion.It can realize the direct conversion of heat energy and electric energy,and play an important role in waste heat recovery and power generation.half-Heusler thermoelectric materials have the advantages of relatively simple chemical composition,no toxic elements,high element abundance,excellent thermal stability,mechanical properties and thermoelectric properties.Therefore,a large number of scholars believe that it is one of the most promising large-scale commercial thermoelectric materials.In this thesis,Ti Ni Sn thermoelectric materials are rapidly prepared by means of ball milling,microwave synthesis and quenching combined with SPS sintering and annealing.The effects of Zr O₂,excessive Ni and Sb light doping on the thermoelectric transport properties of Ti Ni Sn were studied.For the material,XRD,FSEM and EDS were used for the material image analysis,microscopic characterization and elemental analysis respectively,and combined with the resistivity,Seebeck coefficient and thermal conductivity,the thermoelectric properties of the sample were analyzed and evaluated.(1)The effect of Zr O₂nanoparticles on the thermoelectric properties of Ti Ni Sn materials was studied.The results show that the main phase of all samples is still half-Hessler compound,and its element distribution is uniform,and there is no element enrichment area;the resistivity of Ti Ni Sn-5 vol%Zr O₂sample has the most obvious drop,and it is only 4.4??m at 873K.The Seebeck coefficient has also decreased.The maximum Seebeck coefficient is Ti Ni Sn-3 vol%Zr O₂,which is-93.62?VK^-1;among all samples,the power factor of Ti Ni Sn-3 vol%Zr O₂is the highest 1400?Wm^-1K^-2,which is purer than the literature.Like(1150?Wm^-1K^-2),the power factor is increased by 22%.(2)The influence of excessive Ni elements on the thermoelectric properties of Ti Ni Sn material is studied.The results show that the main peak of all samples is Ti Ni Sn,and the Ti Ni_1.025Sn sample does not contain any Full-Heusler;while a small amount of Full-Heusler is found in Ti Ni_1.045Sn and Ti Ni_1.065Sn samples.The resistivity of the Ti Ni_1.065Sn sample decreases more.In the temperature range from room temperature to873 K,the resistivity of the sample is lower than 6??m,which is about 75%lower than the pure sample in the literature.At the same time,the introduction of excessive Ni has a greater impact on the Seebeck coefficient.Small;the highest power factor of Ti Ni_1.025Sn in the sample is 2560?Wm^-1K^-2,which is 2.2 times higher than the pure sample in the literature.The thermal conductivity of the sample increased after the introduction of excessive Ni,and the thermal conductivity of the Ti Ni_1.025Sn sample was the lowest 2.84Wm^-1K^-1.Among all the samples,the maximum ZT value of Ti Ni_1.025Sn is 0.37,which is19%higher than the ZT value(0.31)of the pure sample in the literature.(3)The influence of lightly doped Sb on the thermoelectric properties of Ti Ni Sn material is studied.The results show that the main phase of the sample is Ti Ni Sn,and no impurity diffraction peak is found.At room temperature to 873 K temperature range,all sample resistivity is lower than 5.5??m,including sample Ti Ni Sn_0.955Sb_0.045low resistivity of only 2.2??m,at the same samples Ti Ni Sn_0.985Sb_0.015has high seebeck coefficient,which is-134.6?VK^-1;The Ti Ni Sn_0.965Sb_0.035power factor was the largest of3125.9?Wm^-1K^-2,and the Ti Ni Sn_0.955Sb_0.045thermal conductivity was the lowest of 4.2Wm^-1K^-1.The maximum ZT value was 0.57,which was nearly 30%higher than the highest ZT value(0.44)of similar doped samples in the literature.