Effect Of Co And Ti On Microstructure And Properties Of Ni-Mn-Sn Heusler Thermoelectric Alloy

As a new type of energy material,Heusler-type alloys have attracted wide attention due to their high crystal structure symmetry and good pyroelectricity.This article is based on the excellent performance of Heusler-type alloys to study.Using powder metallurgy technology and vacuum smelting to prepare the Ni-Mn-Sn series block material with alloy element Co and Ti doped,and by heat treatment.The influence of doped alloy elements on the structure and thermoelectric properties of Ni-based Heusler alloy was studied under different temperature conditions.The main findings are as follows:Firstly,the effects of Co and Ti doping on the microstructure and thermoelectric properties of Ni₅₀Mn₃₉Sn₁₁1 alloy were studied.The results show that after smelting,the Co and Ti elements entered into the crystal position of Ni,forming a solid solution,and all specimens were found of the striated martensite and the second phase of the dendrite.the appropriate thermoelectric properties can be improved by doping with appropriate amounts of Co and Ti,the thermal conductivity of the sample decreases with the increase of the doping amount.This is because the doping of Co and Ti elements replaces the Ni element,the crystal defects and disordered arrangement of atoms were introduced into the crystal position of the original Ni atoms.The thermal conductivity is significantly reduced due to the enhancement of phonon scattering,and the conductivity and Seebeck coefficient of the alloy are both increased.Due to the appropriate increase in the amount of doping,the mobility of carrier is increased,and the conductivity increases with the increase of doping.Compared to before doping,the thermoelectric figure of merit of the doped sample ZT increased.Secondly,the effects of different melting times on the thermoelectric properties of the Ni-Co?Ti?-Mn-Sn alloys were studied.The results show that the thermoelectric properties of the samples are better after smelting twice,while the thermal conductivity is reduced.The absolute value of the conductivity and the Seebeck coefficient has also been correspondingly improved compared to a single smelting.After smelting twice,the defects increased,the precipitation of the component segregation heterophase at the grain boundary and the crystal lattice distorted,resulting in a second phase.As the temperature gradually increased,the interaction between the phonon and the phonon proceeded.Enhanced,enhanced scattering,has an impact on its mean free path,resulting in a decrease in thermal conductivity,a certain influence on the electrical conductivity of the sample and the Seebeck coefficient,and eventually resulting in superior value of the thermoelectricity ZT higher than after a smelting ZT value.Thirdly,the effect of different temperatures on the thermoelectric properties of the Ni-Co?Ti?-Mn-Sn alloys was studied.The experimental results show that with the increase of temperature,the thermal conductivity showed an increasing trend,while the Seebeck coefficient decreased first and then increased.