A Study Of The Synthesis Of The Heusler Alloy Co₂FeZ（Z=Sn, Al, Si） By Electrodeposition And Solid Phase Method

X2YZ-type Heusler alloys have excellent properties as the novel magnetic functional materials, and have attracted great interest due to the diversity of the structure and physical properties. So far, a variety of Heusler alloys were prepared by arc melting, high temperature hydrogen reduction, molecular beam epitaxy, sputtering and other methods. In this work, Heusler alloy Co2FeSn thin films were synthesized by electrochemical deposition method which is low cost, flexible and controllable. Co2FeAl and Co2FeSi nanoparticles were prepared by the solid phase method that is a very simple process. And the structures and properties of Co2FeSn thin films, Co2FeAl and Co2FeSi nanoparticles were studied. It has important significance for the development of novel Heusler alloys.Firstly, the Heusler alloy Co2FeSn thin films were prepared by electrochemical deposition method. The effect of the ion concentration ratio in the electrolyte, bath pH, deposition time, cathodic current density on the composition, phase structure, surface morphology and magnetic properties of deposited layer were studied. The results show that:at the conditions of bath pH ranging from3to7, the deposition time from5min to45min, the current density less than1.5A/dm2, there are Co-Sn、 Fe-Sn and Sn in the deposits. When the current density is larger than1.5A/dm2, the bcc structure Co-Fe-Sn alloys appeared. When the current density increases from2.0A/dm2to3.0A/dm2, the Fe content in the deposites increases and Sn content in the deposites decrease. When the current density is2.5-3.0A/dm2, the deposites composed of dispersed particles with size of10-40nm. We also investigated the magnetic properites of the samples. It was found that the magnetic anisotropy of deposits were more obvious with the increase of the current density, For the Co2FeSn film which deposited at the current density of2.5A/dm2, the coercivity (Hc) parallel to the surface of films is32Oe and the Mf/Ms parallel to the surface of films is0.16. Finally, we got the optimal bath composition and deposition conditions to obtain Heusler alloy Co2FeSn films:the ion concentration in the electrolyte was CoSO4·7H2O (0.075M), FeSO4·7H2O (0.05M), SnSO4(0.0083M), pH=7.0, temperature T=60℃, deposition time t=5min, the current density is2.5A/dm2. Secondly, a preliminary study of the synthesis of the Heusler alloys Co2FeAl and Co2FeSi nanoparticles using solid state reaction method which is a simple and easy operative process has been conducted. The Co, Fe, Al nanometer powders were grinded and pressed to tablet, then the sample was calcined under the protection of Ar gas. The results indicate that the binary alloy Fe-Co and Al-Co with cubic structure were produced after calcining at500℃for5h. The A2type cubic structure Co2FeAl nanoparticles with the particle size in the20-50run are prepared after calcining at700℃for5h. The Co2FeAl has soft magnetism with the saturation magnetization (Ms) of about105.68emu/g, the remanent magnetization (Mr) about9.08emu/g, the coercivity (Hc) about148.67Gs at room temperature. A small amount of Fe2O3appeared after calcining at800℃for5h. The Co, Fe, Si nanometer powders were grinded and pressed to tablet, then the sample was calcined under the protection of Ar gas. After calcining at430℃for5h, the sample is a mixture phase of Co7Fe3, Fe2O3and a small amount of Feo.gSio.i. After calcining at630℃for5h, the sample is a mixture phase of Fe3Si and Fe2O3. A cubic structure Co2FeSi nanoparticles with particle size of50-250nm were synthesized after calcining at850℃for5h,with a small amount of Fe2O3present.