基于充满型钨青铜结构的温度稳定型高频高介BME MLCC材料

With the development of communication technology, it requires high capacity and temperature-stable and low cost for MLCC. The dielectric with filled tungsten bronze structure shows great promise in high permittivity (≥75) BME MLCC for its high dielectric constant and low dielectric loss. To meet the requirements of high permittivity BME MLCC with stable capacitance towards temperature, which is encoded C0G by EIA, a new dielectric with composition Ba8-3xLn3x-2MgxNb10-xO30 (BLMN) is synthesized. The relation of composition, phase, microstructure and dielectric properties is studied. Effects of dopants on the dielectric properties of BLMN are investigated by the defect chemistry theory. MgO coated BLMN powder is prepared by a heterogeneous precipitation method. The ion occupation, microstructure, and dielectric properties of BLMN sintered in reducing atmosphere are characterized. By establishing core-shell model, the polarization and loss mechanisms of coated BLMN are revealed. The influence of octahedral tilting, ions order-disorder arrangement, interface effects of shell-core structure on temperature coefficient of dielectric constant is researched systematically. After the research mentioned all above, the high permittivity dielectric with temperature stability and low loss, which sintered in reducing atmosphere with Ni electrode, will be provided for multilayer capacitor applications. On the basis of our results, it lays a foundation for the design and development of the high capacity C0G BME MLCC.

随着通信技术的发展，对高频MLCC的容量、温度稳定性及成本提出了更高的要求。高介低损耗的充满型钨青铜结构材料为发展新型的高介(≥75)BME MLCC提供了巨大的应用前景。本项目针对C0G型高介BME MLCC的应用需求，设计出一种新型材料Ba8-3xLn3x-2MgxNb10-xO30(BLMN),首先对该体系进行组成-结构-性能研究；然后利用缺陷化学理论对BLMN进行掺杂改性，在此基础上利用沉淀法制备出MgO包覆的BLMN；系统研究离子占位、显微结构、缺陷与还原性气氛下烧结材料的介电性能之间的关系。建立核-壳结构模型，明确材料的极化和损耗机理；再深入研究氧八面体扭曲、离子有序无序排列及核-壳界面对介电常数温度系数的调控机制，制备出与Ni电极共烧的高介(≥75)低损耗(≤1.5E-3)C0G型介质材料，为高容量C0G型BME MLCC的设计开发奠定基础。

随着通信技术的发展，对高频MLCC的容量、温度稳定性及成本提出了更高的要求。高介低损耗的充满型钨青铜结构材料为发展新型的高介(≥75)BME MLCC提供了巨大的应用前景。本项目针对C0G型高介BME MLCC的应用需求，设计出一种新型材料Ba8-3xLn3x-2MxNb10-xO30(BLMN，Ln=稀土元素，M=Zn或Mg),首先对该体系进行组成-结构-性能研究；然后利用缺陷化学理论对BLnMN进行掺杂改性，系统研究离子占位、显微结构、缺陷及烧结气氛与材料介电性能之间的关系。通过对损耗机理的研究及结构的调控，获得了几种高介低损耗且具有较佳抗还原特性的介质材料。如可在N2-H2还原性气氛中烧结的BLZN-5%MgO陶瓷（εr=98.9，tanδ=0.0037，IR=6.4E11Ω·cm，τε=-963 ppm/℃），在氮气中烧结的BLMN-15% Li3NbO4（εr=124，tanδ=0.00104，τε=-704ppm/℃）。通过对BaO-Ln2O3-TiO2系陶瓷抗还原特性的研究，获得了介电常数温度系数较低的抗还原介质BNST-1%BCB-2%MnCO3，其在还原性气氛中烧结的性能为εr=75.1, tanδ=0.00115, τε=-42.3 ppm/℃且IR=4.56E12Ω·cm，为高容量C0G型BME MLCC的设计开发奠定基础。