Li Jinglei, Li Fei, Li Chao, Yang Guang, Xu Zhuo, Zhang Shujun
Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China.
Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Sci Rep. 2015 Feb 6;5:8295. doi: 10.1038/srep08295.
The (Nb + In) co-doped TiO2 ceramics were synthesized by conventional solid-state sintering (CSSS) and spark plasma sintering (SPS) methods. The phases and microstructures were studied by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy and transmission electron microscopy, indicating that both samples were in pure rutile phase while showing significant difference in grain size. The dielectric and I-V behaviors of SPS and CSSS samples were investigated. Though both possess colossal permittivity (CP), the SPS samples exhibited much higher dielectric permittivity/loss factor and lower breakdown electric field when compared to their CSSS counterparts. To further explore the origin of CP in co-doped TiO2 ceramics, the I-V behavior was studied on single grain and grain boundary in CSSS sample. The nearly ohmic I-V behavior was observed in single grain, while GBs showed nonlinear behavior and much higher resistance. The higher dielectric permittivity and lower breakdown electric field in SPS samples, thus, were thought to be associated with the feature of SPS, by which reduced space charges and/or impurity segregation can be achieved at grain boundaries. The present results support that the grain boundary capacitance effect plays an important role in the CP and nonlinear I-V behavior of (Nb + In) co-doped TiO2 ceramics.
通过传统固态烧结（CSSS）和放电等离子烧结（SPS）方法合成了（Nb + In）共掺杂的TiO₂陶瓷。利用X射线衍射、拉曼光谱、场发射扫描电子显微镜和透射电子显微镜对其相结构和微观结构进行了研究，结果表明，两种样品均为纯金红石相，但晶粒尺寸存在显著差异。研究了SPS和CSSS样品的介电性能和I-V特性。尽管两者都具有巨介电常数（CP），但与CSSS样品相比，SPS样品表现出更高的介电常数/损耗因子和更低的击穿电场。为了进一步探究共掺杂TiO₂陶瓷中CP的起源，对CSSS样品中的单个晶粒和晶界的I-V特性进行了研究。在单个晶粒中观察到近欧姆I-V特性，而晶界表现出非线性特性且电阻更高。因此，SPS样品中较高的介电常数和较低的击穿电场被认为与SPS的特性有关，通过该特性可以在晶界处实现空间电荷的减少和/或杂质偏析。目前的结果支持晶界电容效应在（Nb + In）共掺杂TiO₂陶瓷的CP和非线性I-V特性中起重要作用。
