Abstract Numerous works on ferrites containing three or more divalent cations offer incomplete data thus failing to offer clear correlations between composition and properties. This study describes the magnetic and electrical behaviour of spinel ferrites containing Ni, Cu and Zn. Samples with the general formula Ni 0.n Cu 0.c Zn 0.z Fe 2 O 4 , with all metals varying between 0 and 0.5, were obtained by the co-precipitation method. The structure of the samples was investigated by X-ray diffraction and infrared spectroscopy, confirming the formation of pure spinel ferrites. The lattice parameter calculation and EDX analysis confirm the composition of the samples. The magnetic behaviour of the nanoparticles is, in general, superparamagnetic with few samples that present small coercivity, corresponding to larger crystallite size. The measurements indicate the superparamagnetic size limit to be of about 14 nm, which can be observed for samples with low zinc content. The electrical properties of the nanoparticles vary with the composition with dominant indirect effect through microstructural changes. All samples have a similar behaviour in relation to electrical current frequency, with variations of about one order of magnitude resistivity. The relative permittivity indicates several samples that change behaviour, such as nickel rich samples, that significantly decrease relative permittivity at higher frequencies compared to zinc rich samples with smaller variations. All samples present variations in the presence of water vapour but increased sensitivity towards humidity was observed for nickel rich samples characterized by larger crystallite size and density.

中文翻译：

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用于改进湿度传感器的三次 NiCuZn 铁氧体：系统研究

摘要 关于含有三个或更多二价阳离子的铁氧体的大量研究提供了不完整的数据，因此无法提供成分和性质之间的明确相关性。本研究描述了含 Ni、Cu 和 Zn 的尖晶石铁氧体的磁和电行为。通过共沉淀法获得具有通式 Ni 0.n Cu 0.c Zn 0.z Fe 2 O 4 的样品，所有金属在 0 和 0.5 之间变化。通过 X 射线衍射和红外光谱研究了样品的结构，证实了纯尖晶石铁氧体的形成。晶格参数计算和 EDX 分析确认了样品的组成。纳米颗粒的磁性一般是超顺磁性的，很少有样品表现出小的矫顽力，对应于较大的微晶尺寸。测量结果表明超顺磁性尺寸限制约为 14 nm，这可以在低锌含量的样品中观察到。纳米粒子的电性能随成分变化，通过微观结构变化具有主要的间接影响。所有样品都具有与电流频率相关的相似行为，电阻率的变化约为一个数量级。相对介电常数表明了几个改变行为的样品，例如富镍样品，与变化较小的富锌样品相比，这些样品在较高频率下显着降低了相对介电常数。所有样品在水蒸气存在下都存在变化，但观察到富镍样品对湿度的敏感性增加，其特征在于较大的微晶尺寸和密度。