Preparation Of The Co₂FeSn Heusler Alloy

Heusler alloy have attracted a lot of attention around the world owing to itsunique physics and chemical properties and which have a close relationship with their particular crystal structure and chemistry composition.It can be achieved by the arc melting,high temperature hydrogen reduction,molecular beam epitaxy for high performance Heusler alloy.In this work a cheap,convenient approach which was known as low-temperature solution-mediated synthesis has been used to prepare Co₂FeSn alloy.The synthetic progress and properties of sample have also been investigated.The low-temperature solution-mediated synthesis has widely used in synthesis of potential Heusler alloys which show similar chemistry composition.These extension in synthetic method meant a lot to further preparation and investigation of Heusler alloy.The first part of our work is the synthesis of Co₂FeSn alloy particles using hydrothermal method.After modulating the type of reducing agent,salt,sodium hydroxide concentration and reaction temperature the main products were CoSn2 and metallic oxide.The second part of our work is the synthesis of Co₂FeSn alloy particles using low-temperature solution-mediated method.Firstly,Co₂Fe nanoparticles was synthesized by using solution reduction method with hydrazine hydrate as the reductant.Then,the influences of the reaction temperature,concentration of sodium hydroxide and surfactant on the microstructure of the samples were investigated.The results showed that the particle size decreased with the decrease of reaction temperature and concentration of sodium hydroxide and the increase of concentration of surfactant.The branch-like Co₂Fe with the particle size of several micrometer and the cubic shape Co₂Fe with the particle size of 50-100 nm were obtained.Meanwhile,we prepared Co₂Fe nanoparticles with the particle size of nearly 10 nm and nice dispersion by ultrasonic-assisted method using FeCl3 as iron source.The products showed micrometer-scale particle size and bcc structure with using Fe2+ as iron source.The saturation magnetization and coercivity of these products were around 180 emu/g and 100 Oe.The Sn nanoparticles were synthesized by solution reduction method with stannous octoate as tin source.The Sn nanoparticles exhibited particle size between 20-40 nm but with local agglomeration.At last the Co₂FeSn particles were prepared by low-temperature solution-mediated method with Co₂Fe and Sn particles synthesized as above.The Co₂FeSn with micro-scale were synthesized by using branch-like and nano-scale Co₂Fe particles under 270? and 215?.The influences of reaction time and temperature on the structure and morphology of the samples were investigated.The results showed that the products synthesized with micro-scale Co₂Fe particles need higher reaction temperature?270 ??and longer reaction time?48 hours?.The reaction time and temperature reduced to 25 hours and 215 ? when using Co₂Fe particles with 10 nm and nano-scale Sn particles.The results suggested that reducing the particle size of Co₂Fe and Sn can reduce the reaction time and increase the dispersion of Sn element in products.