Effects of Secondary Phases on the High-Performance Colossal Permittivity in Titanium Dioxide Ceramics.
Effects of Secondary Phases on the High-Performance Colossal Permittivity in Titanium Dioxide Ceramics.
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DOI：
10.1021/acsami.7b18356
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发表时间：
2018-01
影响因子：
9.5
通讯作者：
Chunlin Zhao;Jiagang Wu
中科院分区：
文献类型：
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作者：
Chunlin Zhao;Jiagang Wu
微电子和储能应用的强烈需求正在推动对大介电常数（CP）材料的研究不断增加。在本研究中，我们设计了一种新的Dy和Nb共掺杂TiO2陶瓷系统[(Dy0.5Nb0.5)xTi1-xO2]，并形成第二相，然后在0.5≤x≤5%的宽组成范围内实现了整体介电性能的增强（εr∼5.0-6.5×104和tanδ<8%）。更重要的是，从缺陷偶极子和内势垒层电容（IBLC）效应的角度探讨了第二相对微观结构、介电性能和稳定性的影响。根据缺陷偶极子理论，CP应主要来源于Nb5+，而Dy3+对介电损耗的降低有很大贡献。 Dy3+和Nb5+共掺杂获得了CP和低介电损耗。此外，Dy的富集诱导了第二相的形成，第二相被认为是分散到陶瓷基体中的低损耗单元，并且很大程度上促进了介电损耗的降低。特别是，与温度相关的复阻抗谱的分析表明，在适当的第二相含量下，晶界电阻增加引起的更强的IBLC效应也有助于优化CP和降低介电损耗。
The intensive demands of microelectronics and energy-storage applications are driving the increasing investigations on the colossal permittivity (CP) materials. In this study, we designed a new system of Dy and Nb co-doped TiO2 ceramics [(Dy0.5Nb0.5)xTi1-xO2] with the formation of secondary phases, and then the enhancement of overall dielectric properties (εr ∼ 5.0-6.5 × 104 and tan δ < 8%) was realized in the broad composition range of 0.5 ≤ x ≤ 5%. More importantly, effects of secondary phases on microstructure, dielectric properties, and stability were explored from the views of defect-dipoles and internal barrier layer capacitance (IBLC) effect. According to the defect-dipoles theory, the CP should mainly originate from Nb5+, and the Dy3+ largely contributes to the decreased dielectric loss. Both CP and low dielectric loss were obtained for co-doping with Dy3+ and Nb5+. Besides, the Dy enrichment induced the formation of secondary phases, which were regarded as the low loss unit dispersed into the ceramic matrix, and largely facilitate the decreased dielectric loss. In particular, the analysis of temperature-dependent complex impedance spectra indicated that a stronger IBLC effect caused by the increased grain boundary resistance can also contribute to the optimized CP and low dielectric loss under appropriate contents of secondary phases.