batio3核-壳纳米复合材料的高频介电谱：相互扩散问题
High-frequency dielectric spectroscopy of batio3 core - silica shell nanocomposites: Problem of interdiffusion
摘要：
采用标准烧结法、放电等离子烧结法和两步烧结法制备了三种BaTiO 3核-非晶纳米壳复合陶瓷，并采用XRD、HRSEM和10^3 - 10^13 Hz（包括THz和IR）宽带介电谱对其进行了表征。不同的样品的孔隙度和相互扩散的量从核壳，在相关的孔隙度增加。还使用基于有效介质近似的合适的模型计算了介电谱。测量结果显示，在THz范围以下存在较强的介电色散，这无法通过建模来解释，并且其强度与相互扩散的程度相关。我们将其分配给相互扩散层的影响，引起强烈的界面极化。看来，高频介电谱是一个非常敏感的工具，用于检测任何梯度层和样品的不均匀性，即使在介电材料具有可忽略的电导率。
英文摘要：
Three types of BaTiO3 core - amorphous nano-shell composite ceramics were processed from the same core-shell powder by standard sintering, spark-plasma sintering and two-step sintering techniques and characterized by XRD, HRSEM and broad-band dielectric spectroscopy in the frequency range 10^3 - 10^13 Hz including the THz and IR range. The samples differed by porosity and by the amount of interdiffusion from the cores to shells, in correlation with their increasing porosity. The dielectric spectra were also calculated using suitable models based on effective medium approximation. The measurements revealed a strong dielectric dispersion below the THz range, which cannot be explained by the modeling, and whose strength was in correlation with the degree of interdiffusion. We assigned it to an effect of the interdiffusion layers, giving rise to a strong interfacial polarization. It appears that the high-frequency dielectric spectroscopy is an extremely sensitive tool for detection of any gradient layers and sample inhomogeneities even in dielectric materials with negligible conductivity.
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