B位复合尖晶石陶瓷的有序/无序相变、畴结构、缺陷与微波介电性能的研究

In our preliminary study, B site complex spinel ceramics exhibit low cost of raw materials, low bulk densities, low sintering temperatures and excellent dielectric properties, which is a type of novel microwave dielectric ceramic with having a potential application. However, the researches on the formating and controlling mechanisms of dielectric loss of ceramics are very limit. In this project, B site complex spinel ceramics will be studied by using the achievement of theoretic research of perovskite and tungsten bronze materials. Firstly, the intrinsic dielectric constant and loss of ceramics will be studied by first principle and far-infrared reflectance spectroscopy, and the origin of dielectric loss of materials will be revealed. Secondly, the intrinsic stress, ordered/disordered phase transition, ordering degree, ordering domain and point defects of ceramics will be studied using in-situ XRD, Raman and TEM. The relationship between the dielectric loss and the above factors will be discussed. The intrinsic mechanism of the composition, microstructure and preparation technology on the performance will be revealed. Finally, the novel spinel microwave dielectric ceramics with ultralow dielectric loss will be obtained. The accomplishment of this project will provide a deep understanding on a series of scientific problems about the relationship between the design, preparation, structure and properties of the microwave dielectric materials, which enriches the microwave dielectric theory.

申请者在前期研究工作中发现，B位复合尖晶石陶瓷具有原料便宜、密度小、烧结温度低以及介电性能优异等优点，是一类极具应用潜力的微波介电陶瓷新体系，但目前对该类材料介电损耗的形成机制及其调控机理的研究还很有限。本项目以其为研究对象，借鉴钙钛矿、钨青铜等材料体系的理论研究成果，通过第一性原理和远红外反射光谱研究材料的本征介电常数及介电损耗，揭示该类材料介电损耗的起源。利用原位XRD、Raman光谱、TEM等方法系统研究陶瓷内应力、有序/无序相变、有序度及有序畴、点缺陷等，并探讨以上因素与材料介电损耗的内在关联性，揭示该类材料的组成、微结构和制备工艺对性能的内在影响机制，进而优化材料的微波介电性能，以期获得超低损耗的新型尖晶石微波介电陶瓷。本项目的顺利实施，可以深入认识微波介电材料设计、制备、结构与性能之间的关系等科学问题，丰富微波电介质理论。

现代移动通讯技术的飞速发展对介质材料的性能提出了更高的要求，探索新型高性能微波介质陶瓷意义重大。本项目以尖晶石等材料体系为研究对象，首先，系统研究了Li4Ti5O12陶瓷的烧结特性、相结构演变以及微波介电性能，揭示了其性能与结构演变之间的内在关系。在此基础上，以Li4/3Ti5/3O4与M2TiO4或MAl2O4(M=Zn, Mg, Co)为组元，设计制备了Li4x/3Co2-2xTi1+2x/3O4、Li4/5Mg4/5Ti7/5O4、Li4xMg3(1-x)Al6(1-x)Ti5xO12、ZnAl2O4-Li4Ti5O12等系列高性能微波介质材料，揭示了材料介电损耗的形成机制及其调控机理。以Li2MgTi3O8为基础，通过改变TiO2的含量，有效调控了Li2O-MgO-nTiO2材料体系的相结构、烧结特性以及微波介电性能，获得了一种高性能微波介质陶瓷。通过掺杂少量的BaCu(B2O5)，成功将Li4/5Mg4/5Ti7/5O4的烧结温度降至~900℃，降温后的材料保持优异的微波介电性能且能与Ag实现共烧匹配，是一类LTCC器件的备选材料。最后，通过对粉体原料进行球磨预处理，采用微结构调控技术有效拓宽了Li2MTi3O8(M=Zn、Mg)、LiZnNbO4尖晶石及Li2MgTiO4岩盐结构陶瓷的烧结温度范围，优化了材料的微波介电性能。此外，本项目也进行了横向延伸，首先对2Li2O-AO-3WO3、4BaO-4SiO2-V2O5、5MgO-3Li2O-4WO3、M2BiLi2V3O12 (M = Zn, Ca)、MgO–xB2O3–yBaCu(B2O5)以及NaMg4V3O12等低温烧结微波介质陶瓷进行了较为系统的研究，揭示了材料微结构对性能的内在调控机制，获得了系列新型LTCC材料。其次，设计制备了Mg1-xLi2xTixO1+2x、 Ba4MTi11O27(M=Co、Cu)、0.95MgTiO3-0.05CaTiO3、CaMgSiO4、Mg2B2O5、MgAl2Ti3O10、(3MgO–Al2O3–3TiO2)–CaTiO3、ZnO-TiO2-ZrO2-Nb2O5等新型微波材料，系统研究了其烧结特性、相结构、微观形貌以及微波介电性能，揭示了材料“结构-性能”之间的内在关系。最后对K0.5Na05NbO3基陶瓷进行了研究，获得了一种高温度稳定型的高介低损介电材料。