钛酸钡基复合材料体系的界面效应及其介电调谐性能研究

Barium titanate (BaTiO3) is one of the most important materials in electronic ceramics. Under DC electric field, the capacitance and loss of BaTiO3-based materials usually decrease with the increase of applied electric field, and finally tend to be stable. This phenomenon is called dielectric tunability, and can be used in the dielectric phase shifter which is the key components of phased array radar. In this project, BaTiO3-based composite materials are chosen as the object of study. The relationship between interfacial effects and the dielectric performances of BaTiO3-based composite materials are specifically investigated, and the theoretical model of dielectric tunability responses is established. To be detail, firstly, the 0-3, 2-2 and 1-3 type of BaTiO3 based composites are prepared. Secondly, the composition, structure, morphology and stress state of the interface between both phases are studied, and the interfacial polarization response and the tunneling mechanism of carrier under strong dc field are revealed. Finally, the effects of complex configuration, type, size and morphology of the second phase on the performance of dielectric tunability are studied. And theoretical model between the dielectric performance and complex configuration, properties and shape parameters of the second phase is established.

钛酸钡（BaTiO3）是电子陶瓷中最为重要的基础材料之一，在直流电场下，材料的电容和损耗通常都会随外加电场的增加而减小，而最终趋于稳定，这一现象称之为介电调谐，其可用于相控阵雷达的关键器件介质移相器中。本项目拟以BaTiO3基复合材料体系为研究对象，研究复合材料的界面效应与介电调谐性能之间的相互关系，建立复合材料介电调谐性能的理论模型。首先，研究0-3型、2-2型及1-3型BaTiO3基复合材料的制备工艺；其次，研究两相界面的成分、结构、形貌及应力状态，揭示强直流电场作用下两相界面处的极化响应及载流子的隧穿机理；最后，研究复合构型、第二相的类型、尺寸与形貌对复合材料的介电调谐性能的影响规律，建立介电调谐性能与复合构型、第二相的性质及形状参数之间的理论模型。

军用雷达技术的发展迫切需要一种介电常数适中，调谐率高、介电损耗小并且温度稳定性好的介电调谐材料。本项目首先采用传统的固相烧结及放电等离子烧结技术制备了(Ba0.4Sr0.6)TiO3/Y2O3、Ba(Ti0.85Sn0.15)/MgO 0-3型复合陶瓷，通过控制升温速率与保温时间抑制界面扩散，并通过控制第二相的粒径与微观形貌提高复合陶瓷的击穿场强，从而获得了一种具有较高的介电调谐率与较低的介电损耗的介电调谐材料；其次采用流延及叠烧工艺制备了不同浓度La3+掺杂BaTiO3的2-2型复合厚膜，这种成分梯度厚膜由于膜层之间的均化作用能有效提高材料介电性能及调谐性能的温度稳定性，其居里峰显著宽化，介电损耗降至0.01以下，在25到75 oC的范围内，调谐率始终保持在35%以上；最后分别采用固相法和化学法制备了BaTiO3及Ba0.6Sr0.4TiO3粉体，再通过流延法制备了BaTiO3/PVDF和(Ba0.6Sr0.4)TiO3/PVDF复合厚膜，通过对比粉体的填充量、粒径及分散性对复合厚膜的介电调谐性能的影响，揭示了陶瓷/聚合物复合材料介电调谐性能调控的一般规律。

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