高介电材料综述报告

高介电常数材料

——专题报告

杨宇

2013/12/21

高介电宏观上表现在高的耐击穿电压、好的绝缘性

•传统高介电材料：铁电陶瓷材料和聚合物材料。两者都存在着弊端

•新型高介电材料：以高介电陶瓷粒子或金属导体粒子填充的聚合物基复合材料

填充材料基体材料界面性质

1.功能填料对介电性能的影响•由于聚合物基体的介电常数通常都不高，因此功能填料是决定聚合物基复合材料介电性能的关键组分。

•它们的种类、结构、粒径大小和形貌均对材料的介电性能产生明显影响

1.1功能填料的种类

•1.1.1无机导体填料

•主要依据逾渗理论

•式中，p为孤立的分散相的体积分数，p c为逾渗阈值，且p<p c

•Polyvinylidene fluoride (PVDF) composites filled by self-passivated zinc (Zn) particles High dielectric constant composite.

It's considered that high dielectric constant is originated from the enhanced interfacial polarization, while the low loss is due mainly to the self-passivation layer of zinc carbonate hydroxide, which can serve as the insulating interface and reduce leakage current effectively through blocking the free transfer of charge carriers between adjacent Zn fillers.

GO shells around CNTs cannot only effectively improve the dispersion of CNTs,but also work as insulation barriers for reducing dielectric loss factor and increasing break down strength.

The MWCNTs were coated with polypyrrole(PPy) by an inverse microemulsion polymerization.

Our composites presented a stable high dielectric constant(44),rather low

loss(<0.07).The largely enhanced dielectric performance originates from the organic shell PPy,which not only ensure good dispersion of MWCNTs in the polymer matrix but also screen charge movement to shut off leakage current.

对于陶瓷，要达到很高的介电常数，填充量很高，分散性降低，介电损耗很高，加工性能较差。在常温下介电常数不超过100。目前改进的方法主要有:控制填料的分散性。填料的团聚会给复合材料的电学性能以及力学性能带来很大的影响，因此填料的分散是改善介电性能的一个很重要的因素。

1.1.3有机半导体填料

For example, in P(VDF -TrFE)-g-CuPc, it reaches about 100 at 100 Hz, representing a more than 6 times increase compared with the P(VDF -TrFE) matrix. The dielectric constant of the composites is enhanced by CuPc oligomer.

2.填料形貌及尺寸的影响

Ang对填料的形貌专门进行了研究，运用有限元法对圆形、三角形和环形的填料粒子分别进行计算分析发现，在同等填充

比的情况下，介电常数:圆形<三角形< 环形

填料尺寸对复合材料的介电性能也有很大的影响。颗粒尺寸越小，填料就越容易与聚合物实现均匀混合。另外，颗粒尺寸越小，颗粒与聚合物基体间的界面就越多，在极化过程中，界面极化效应就越显著，从而极大地提高了介电性能.

•A PANI/epoxy composite prepared in this fashion reached a high dielectric constant close to 3000, a dielectric loss tangent less than 0.5at room temperature and 10 kHz.