Investigation of electric transport behavior of bulk CoFe2O4 by complex impedance spectroscopy
Investigation of electric transport behavior of bulk CoFe2O4 by complex impedance spectroscopy
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DOI：
10.1016/j.jallcom.2013.10.195
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发表时间：
2014-02
影响因子：
6.2
通讯作者：
R. Panda;D. Behera
中科院分区：
文献类型：
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作者：
R. Panda;D. Behera
通过传统陶瓷路线合成的钴铁氧体从X射线衍射图中证实了其为单一相，在扫描电子显微镜图像中发现了微米范围内的良好晶粒生长。该研究首次揭示了在30 °C-250 °C的温度范围内，CoFe 2 O 4中晶粒和界面（晶界和电极接触）的演变效应作为100 Hz-1 MHz频率的函数。在虚阻抗图中出现低温（<75 °C）弛豫峰，这归因于晶粒效应。在高温范围内观察到两组峰共存。这种共存与在75 °C <$T <$175 °C温度范围内发现的晶粒和晶界以及在200 °C <$T <$250 °C温度范围内发现的晶界和电极效应有关。奈奎斯特图显示了175 °C和200 °C下的三个不同的温度曲线。阻抗行为已被建模为T = 175 °C时的RC-RC-RQ和T = 200 °C时的RC-RQ-RQ的等效电路。本文首次报道了用KWW（Kohlrausch-Williams-Watts）函数拟合钴铁氧体虚电模量谱的双峰，计算得到的伸缩指数因子β。结果表明，晶粒和晶界的βg= 0.62，βgb= 0.86。Maxwell-Wagner极化是介电行为的原因。高的介电常数和电导率已被解释的帮助下，铁和钴离子的可变氧化态的交换相互作用。
Cobalt ferrite synthesized by a conventional ceramic route had confirmed its single phase from XRD pattern and well grain growth of micrometer range was found in SEM image. The study exposes for first time, the evolution of grains and interfaces (grain boundaries and electrode contact) effect in bulk CoFe2O4in the temperature range 30 °C–250 °C as a function of frequencies varying from 100 Hz–1 MHz. The low temperature (<75 °C) relaxation peak appears in imaginary impedance plot attributes to grain effect. Two sets of coexistence of peaks is observed at elevated temperature range. The coexistence is related to grains and grain boundaries found in temperature domain 75 °C ⩽T⩽ 175 °C and again grain boundaries and electrode effect in domain 200 °C ⩽T⩽ 250 °C. The Nyquist diagram shows three distinct semicircles at 175 °C and 200 °C. The impedance behavior has been modeled with equivalent circuit of RC–RC–RQ forT⩽ 175 °C and RC–RQ–RQ forT⩾ 200 °C. The stretching exponential factorβcalculated from the well fitted double peaks of imaginary electric modulus spectra with KWW (Kohlrausch–Williams–Watts) function of bulk cobalt ferrite, is reported first time in our work. We foundβg= 0.62 andβgb= 0.86 for grains and grain boundaries respectively. The Maxwell–Wagner polarization is responsible for the dielectric behavior. The high permittivity and conductivity has been explained by the help of exchange interaction of variable oxidation states of iron and cobalt ions.