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首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Nanocrystalline Mn–Zn ferrites from mixed oxalates: Synthesis, stability and magnetic properties
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Nanocrystalline Mn–Zn ferrites from mixed oxalates: Synthesis, stability and magnetic properties

机译：混合草酸盐的纳米晶锰锌铁氧体：合成，稳定性和磁性

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摘要

Nanocrystalline Mn–Zn ferrite spinel powders were synthesized by thermal decomposition of mixed β-(Mn, Zn, Fe)(C_2O_4)·2H_2O oxalate. Thermolysis of the oxalate for 2 h at 300 ℃ in air yields an amorphous product, whereas at 400 and 500℃ ferrite spinels with unit cell parameters of 8.394(7) and 8.495(3) A, respectively, are formed. Decomposition of the oxalate at 500℃ for 24 h results in a mixture of haematite and a Fe-poor spinel revealing the metastability of the nanocrystalline spinel at that temperature. The crystallite sizes are 12 and 45nm for ferrite spinel powders synthesized at 400 and 500 ℃, respectively.Zero ferrous ion concentrations were measured by redox titration, suggesting that the ferrites are defect spinels containing Fe3+ and cation vacancies. Thermal analysis and XRD demonstrate that the ferrites undergo several phase transitions during annealing in air. Magnetic measurements reveal that the saturation magnetization at 5K of the ferrites increases with crystallite size. Hysteresis loops measurements demonstrate superparamagnetic behavior at room temperature of the nanocrystalline powder obtained at 300℃. Mossbauer spectroscopy at room temperature confirms the superparamagnetic character of that sample. The ferrites obtained at 400 and 500 ℃, however,represent a mixture of small superparamagnetic and larger ferrimagnetic particles.
机译：通过混合分解β-（Mn，Zn，Fe）（C_2O_4）·2H_2O草酸盐合成纳米晶锰锌铁氧体尖晶石粉。草酸盐在空气中在300℃下热解2 h会生成无定形产物，而在400和500℃时会形成晶胞参数分别为8.394（7）和8.495（3）A的铁素体尖晶石。草酸盐在500℃下分解24小时会导致赤铁矿和贫铁尖晶石的混合物，显示出该温度下纳米晶尖晶石的亚稳定性。分别在400和500℃下合成的铁氧体尖晶石粉末的微晶尺寸分别为12nm和45nm。通过氧化还原滴定法测量零铁离子浓度，表明该铁氧体是含有Fe 3+和阳离子空位的缺陷尖晶石。热分析和XRD分析表明，铁素体在空气中退火过程中经历了几个相变。磁性测量表明，铁素体在5K时的饱和磁化强度随微晶尺寸的增加而增加。磁滞回线测量结果表明，在300℃下获得的纳米晶粉末在室温下具有超顺磁性能。室温下的Mossbauer光谱证实了该样品的超顺磁性。然而，在400和500℃下获得的铁氧体代表小超顺磁性颗粒和大亚铁磁性颗粒的混合物。

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