Simulation of Impedance Spectra for Core-Shell Grain Structures Using FiniteElement Modeling
Simulation of Impedance Spectra for Core-Shell Grain Structures Using FiniteElement Modeling
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DOI：
10.1111/jace.13533
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发表时间：
2015-06-01
影响因子：
3.9
通讯作者：
Sinclair, Derek C.
中科院分区：
文献类型：
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作者：
Heath, James P.;Dean, Julian S.;Sinclair, Derek C.
核壳区体积分数是控制BaTiO3等核壳微结构电陶瓷温度依赖性电学性能的重要参数。在这里，我们强调了使用电容比（通过模拟阻抗谱获得）来提取两个区域的精确体积分数的潜在不可靠性。采用有限元方法模拟了两个微观结构：一个近似于核壳结构（封装模型）和一个串联层模型（SLM）。在一定的输入体积分数范围内，模拟了微结构的阻抗响应。模拟得到的体积分数与SLM微结构的输入值一致，但与封闭模型的输入值不同。电流密度和电场图显示，这种差异是由封装模型的物理和电学微观结构的差异引起的。电流密度的流迹分析表明，电流沿着通过芯的最小电阻路径，留下电流密度较低的壳区。当试图从具有小岩心的封闭微结构中提取体积分数时，这些差异是重要的。在本例中，岩心体积分数小于0.7会产生超过25%的差异。
The volume fraction of core- and shell-regions is an important parameter in the control of temperature-dependent electrical properties of core-shell-microstructured electroceramics such as BaTiO3. Here, we highlight the potential unreliability of using capacitance ratios, obtained by simulating impedance spectra, to extract accurate volume fractions of the two regions. Two microstructures were simulated using a finite element approach: an approximation to a core-shell structure (the encased model) and a series-layer model (SLM). The impedance response of the microstructures was simulated for a range of input volume fractions. The volume fractions obtained from the simulation agreed with the input values for the SLM microstructure but differed for the encased model. Current density and electric field plots revealed that this discrepancy was caused by differences between the physical and electrical microstructures of the encased model. A stream trace analysis of current density demonstrated that the current follows the path of least resistance through the core, leaving regions of shell with lower current density. These differences are important when attempting to extract volume fractions from encased microstructures with small cores. In the present case, core volume fractions less than 0.7 produce differences in excess of 25%.