针状纳米晶复合SrM铁氧体的制备及磁性研究

Preparation and Magnetic Properties of Needle-Like Nano-Composite SrM Ferrite

采用柠檬酸法和EDTA-柠檬酸联合络合法分别制备球状和针状纳米晶复合SrM铁氧体。用透射电镜、X射线衍射仪和振动样品磁强计对合成样品的粒度及形貌、物相、磁学性能进行研究。结果表明:当煅烧温度为850℃时,样品为纯的M型六角锶铁氧体,且矫顽力达到最大;当温度低于850℃时,样品存在复相,直接煅烧的样品为SrFe12O19/α-Fe2O3纳米复合相,通过自蔓延燃烧处理的样品为SrFe12O19/γ-Fe2O3的纳米复合相。在750℃时制得的样品与纯的M型六角锶铁氧体相比,剩余磁化强度和饱和磁化强度有所提高。通过加入EDTA使锶铁氧体的形貌发生改变,矫顽力得到提高,最终制得粒径为30nm,长径比为5:1,内禀矫顽力、比饱和磁化强度与比剩余磁化强度分别为6198.3×79.6A·m-1、71.5A·m2·kg-1和42.3A·m2·kg-1的针状纳米复合SrM铁氧体。

Spherical and needle-like nano-composite SrM ferrite were prepared by citric acid method and citric acid-EDTA co-complexion method, respectively. The morphology, particle size, crystal phase and magnetic properties of different samples were analyzed by transmission electron microscope （TEM）, X-ray diffraction（XRD） and vibration sample magnetometer （VSM）, respectively. The result indicates, when the calcination temperature is 850 ℃, pure hexagonal strontium ferrite samples are prepared, and the coercivity （He） can be at the maximum scale. When the calcination temperature is below 850 ℃, there are heterogeneous phases in the samples; SrFe12O19/α-Fe2O3 nano-complex and SrFel2019/γ-Fe2O3 nano-complex are prepared by direct calcination and calcination after self-propagating combustion, respectively. The saturation magnetization （Ms） and remanent magnetization （Mr） of nano-composite SrM ferrite prepared at 750 ℃ are all superior. The morphology is changed by adding EDTA, and Hc increases. The diameter and aspect ratio of the samples are 30 nm and 5：1, respectively. He, Ms and Mr of needle-like nano-composite SrM ferrites are 6198.3×79.6 A·m^-1, 71.5 A·m^2·kg^-1 and 42.3 A·m^2·kg^-1, respectively.