Effects of cobalt substitution on the structural and magnetic properties of cobalt-nickel ferrite nanoparticles synthesized by the co-precipitation method

冯金地 FJD


利用共沉淀法成功地合成了(x=0、0.2、0.4、0.6和0.8)纳米颗粒并进行了退火处理.对样品进行了XRD、FT-IR、TG-DSC和VSM等表征.结果显示,样品前驱体中存在少量的杂质如吸收水和硝酸盐,退火处理是获得单相和高度结晶Co-Ni尖晶石铁氧体的必备条件.所有退火样品均是单相立方尖晶石结构纳米晶粒,其平均尺寸在40~60nm的范围.晶格常数随着Co掺杂含量增加而增加.比表面积测试显示Co掺杂量的增加在一定程度上减少了样品的表面体积比,有利于Co-Ni铁氧体的晶粒生长.样品饱和磁化(Ms)和矫顽力(Hc)与钴掺杂量密切相关.Ms值从375emu/g(x=0)增加到620emu/g(x=08),这是由于较高的掺杂Co2+阳离子磁矩的增强导致A和B亚晶格之间的超交换相互作用增强.矫顽力Hc的大小从730 Oe(x=0)到5583 Oe(x=0.8),这主要是由于掺杂Co2+阳离子具有比Ni2+阳离子更大的磁晶各向异性常数.(x=0,0.2,0.4,0.6,and 0.8) nanoparticles were successfully synthesized by the co-precipitation method followed by annealing treatment. The structural and magnetic properties of the samples were determined by X-ray Diffraction(XRD), Fourier Transform Infrared Spectroscopy(FT-IR),Thermogravimetric and Differential Scanning Calorimetry (TG-DSC) and Vibrating Sample Magnetometer (VSM) at room temperature. The results revealed that there was a small amount of impurities such as absorbed water and nitrates in the dried precursors, and annealing treatment is necessary to obtain a single-phase and highly crystallized Co-Ni spinel ferrite. The XRD patterns showed the formation of the single-phase cubic spinel structure for the annealed products, and the average crystallite size was in the range of 40—60 nm. The specific surface area test showed the increase of Co substitution content favors the grain growth of the Co-Ni ferrite nanopowders to some extent by decreasing the volume ratio of the sample's surface. The VSM measurement at RT revealed both the saturation magnetization (Ms) and coercivity (Hc) are highly depending on the cobalt substitution content. The Ms value increases from 37.5 emu/g for x=0 to 62.0 emu/g for x=08 and this was attributed to the doping Co2+ cations with a higher magnetic moment leading to the enhancement of the superexchange interaction between the A and B sublattices. The magnitude of Hc increases from 73.0 Oe for x=0 to 558.3 Oe for x=0.8 and this resulted mainly from the substituted Co2+ cations with a much larger magneto-crystalline anisotropy constant than that of the Ni2+ cations.


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