Microwave assisted processing of X8R nanocrystalline BaTiO3 based ceramic capacitors and multilayer devices
Microwave assisted processing of X8R nanocrystalline BaTiO3 based ceramic capacitors and multilayer devices
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X8R纳米晶BaTiO3基陶瓷电容器和多层器件的微波辅助加工
DOI：
10.1016/j.oceram.2021.100214
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Sumithra S
中科院分区：
文献类型：
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作者：
Sumithra S
BaTiO3基多层陶瓷电容器(MLCC)是电子器件中的重要元件。实现高介电性能、小型化和成本效益仍然是具有挑战性的。另一个关键问题是与金属电极共烧陶瓷层，以及使用昂贵的铂和高Pd含量的化合物作为电极。因此，降低烧结温度和在不影响介电性能的情况下使用更便宜的金属电极是导致MLCCS成本效益的主要因素，这些特点可以很好地应用于下一代低成本高性能电陶瓷器件-这是本研究的主题。在本工作中，我们首先制备并分析了不同BT颗粒尺寸(50 nm、100 nm和200 nm)的BaTiO3(BT)陶瓷的介电性能。在此基础上，利用200 nm BaTiO_3的优异介电性能进行了进一步的研究。然后，为了降低200 nm BaTiO_3陶瓷的烧结温度，提高其介电性能，采用Bi2O_3作为掺杂剂，既能起到助烧作用，又能改善介电性能。还添加了稀土掺杂系统(英国诺尔斯工业合作伙伴的专利)与Bi2O3的组合，以调整BaTiO3的缺陷化学，以进一步提高介电性能。采用非水介质、分散剂和粘结剂体系，研制出了具有最佳流变性的均匀混合的BT基陶瓷浆料体系。还研究了添加玻璃粉以降低烧结温度及其对陶瓷电容器介电性能的影响。这两种材料都是通过干压干燥浆料制得的。采用常规、微波和混合烧结法对电陶瓷器件进行了致密化，并对其密度、显微结构、成分和介电性能进行了系统的表征。传统的烧结会产生不受欢迎的大微米尺寸的表面特征，这对器件的耐用性是不利的，而使用快速微波辅助烧结程序，这些特征的形成和生长已被首次证明是显著减少的。此外，还利用微波方法实现了陶瓷层与价格较低的(Ag/Pd)合金的高效共烧结。合成的BaTiO3基电容式器件具有高介电常数、优异的X8R性能和低的损耗因数，在汽车、传感和空间领域具有广泛的高温应用潜力。
BaTiO3based multilayer ceramic capacitor (MLCC) is an important component in electronic devices. Achieving high dielectric performance, miniaturisation and cost effectiveness are still challenging. Co-sintering ceramic layers with metal electrodes and use of expensive Pt and high-Pd content compositions as electrodes are other key issues. Thus, the major factors that could lead to cost effectiveness of MLCCs are reduction in sintering temperature and using less expensive metal electrodes without compromising dielectric performance and these traits could auger well for the next generation low-cost high performance electroceramic devices – this is the subject matter of the present study.In this work, initially we have fabricated and analysed the dielectric performance of BaTiO3(BT) ceramics with different BT particle sizes (50 nm, 100 nm and 200 nm). Based on results, 200 nm BaTiO3was used for further studies due to its superior dielectric performance. Then, to reduce the sintering temperature and improve the dielectric performance of 200 nm BaTiO3ceramics, Bi2O3was used as a dopant which acts both as a sintering aid and helps to improve the dielectric performance. A combination of rare earth dopant system (proprietary from the industrial partner Knowles, UK) with Bi2O3was also added to tune the defect chemistry of BaTiO3for enhancement in dielectric performance further. A homogeneously mixed BT-based ceramic slurry system (containing the above dopants) with optimum rheology was developed using a non-aqueous medium, dispersant and a binder system. Addition of glass frits for lowering the sintering temperature and its effect on dielectric performance was also investigated on both discs (made using dry pressing of the powders obtained via drying of the slurry) as well as multilayer ceramic capacitors (MLCCs) fabricated through screen printing. Conventional, microwave and hybrid sintering procedures were employed for the densification of the electroceramic devices and these were characterized for density, microstructure, composition and dielectric performance systematically. Conventional sintering resulted in undesired large micron sized surface features which are detrimental to device durability, whereas formation and growth of these features have been demonstrated to be significantly minimised using the rapid microwave assisted sintering procedures for the first time. Further efficient co-sintering of ceramic layers with less expensive (Ag/Pd) alloy has also been accomplished using the microwave methodology. The resultant BaTiO3based capacitive devices exhibited high dielectric permittivity, superior X8R performance and low dissipation factor, asserting their massive potential for widespread high temperature applications in automotive, sensing and space sectors.