高体击穿强度线性介质陶瓷的制备及物性研究

Pulse forming line is an extremely important component in pulse power system. Linear pulse-forming line is the key technology to realize the novel high gradient compact pulse accelerator and low maintenance cost. BaSrTiO3 based dielectric ceramic and glass ceramic have been investigated as potential candidates. However, their low breakdown strength and poor stability restrains their application. Therefore, in this project, we designed a new composite ceramic CaO-TiO2-Al2O3 with high breakdown strength and low dielectric constant. Based on our previous work, SiO2 and MgO will be added to optimize the properties of CaO-TiO2-Al2O3 dielectric ceramic. The nanopowders with double "nuclear - shell" structure will be prepared by sol gel method and liquid phase coating process. Fine controlled microstructure of dielectric ceramic will be obtained by adjusting the powder preparation and sintering process to improve the breakdown strength and reduce the dielectric constant of the materials. The influence of compositions and microstructures of the dielectric ceramic on the breakdown strength and dielectric properties will be investigated. The mechanism of the dielectric breakdown and pulse of life under high-voltage pulsed electric fields will be clarified; the key technique on the preparation of thin and long dielectric ceramic will be solved to developed low linear solid-state pulse forming line with high breakdown strength and to meet the requirement on novel high gradient pulse accelerator.

脉冲形成线是脉冲功率系统中极其重要的部件，固态介质线性脉冲形成线是实现新型高梯度脉冲加速器紧凑型、小型化和低成本维护的关键技术。目前集中研究的BaSrTiO3基介质陶瓷和玻璃陶瓷存在击穿强度低、稳定性差等不足。本项目紧密结合应用需求，设计了一种具有高击穿强度和低介电常数的介质陶瓷新体系CaO-TiO2-Al2O3，在前期工作基础上，添加SiO2和MgO等氧化物进行组成优化设计，采用溶胶凝胶法和液相包裹法相结合，制备双层“核-壳”结构纳米粉体，调节粉体制备和烧结工艺，实现介质陶瓷显微结构的精细调控，提高材料的击穿强度，降低介电常数。研究新型介质陶瓷的组成和微结构对其击穿强度和介电性能的影响规律，阐明高压脉冲电场下介质陶瓷的电击穿及其脉冲寿命的物理机制，解决制备薄长片型介质陶瓷脉冲形成线的关键技术，研制出一种高体击穿强度的低介线性固态脉冲形成线，满足我国新型高梯度脉冲加速器的需求。

脉冲形成线是脉冲功率系统中极其重要的部件，固态介质线性脉冲形成线是实现新型 高梯度脉冲加速器紧凑型、小型化和低成本维护的关键技术。.本项目针对脉冲功率系统对脉冲形成线的任务需求，以CaO-TiO2-Al2O3体系为基，添加变价氧化物Ni2O3、MnO2、La2O3和宽禁带氧化物SiO2、MgO、ZrO2进行多种氧化物掺杂改性和性能优化，已设计出新型的线性介质陶瓷材料体系CaO-TiO2-Al2O3-SiO2-MgO-MO，建立CaO-TiO2-Al2O3新体系线性介质陶瓷的材料组成和微结构之间关联性，改变化学组分，如，加入Ni2O3，液相增多，各相分布更均匀，体积密度增大。当Ni2O3含量从0增加到2.5wt%，陶瓷的烧结温度从1280℃降低到1230℃，陶瓷致密度提高，体积密度从3.122 g/cm3提高到3.175 g/cm3。.已采用溶胶凝胶法和液相包裹法相结合，制备出双层“核-壳”结构的纳米粉体，已采用等静压成型和固相法调控介质陶瓷的局域微结构，制备出高致密、细晶CaO-TiO2-Al2O3体系线性介质陶瓷。将陶瓷耐电强度提高了40%。化学法制粉所得陶瓷的介电性能温度、频率稳定性好，介电常数增大，介电损耗降低。研究了介质陶瓷的组成和微结构对材料击穿强度和介电性能及其稳定性的影响规律，研究了脉冲电场作用下介质陶瓷的介电性能、击穿强度和脉冲寿命随温度、脉冲频率的演变规律，阐明了高压脉冲电场作用下线性介质陶瓷的介电击穿及其脉冲寿命的物理机制。随着厚度的减小，0.8mm以后，陶瓷电击穿强度、抗折强度、弹性模量随厚度的变化呈相似的变化规律，非线性增大，可见陶瓷的电击穿性能与其气孔率和化学键强息息相关。线性介质陶瓷的电击穿物理与晶粒、晶界和非晶相的电导激活能直接关联，激活能越大，电击穿强度越大。最终研制出具有高体击穿强度的新型低介线性脉冲形成线介质陶瓷，直流电阻率高达2.82×1014 Ω·cm，电击穿强度高达82.1 kV/mm。陶瓷介电常数变化不大，介电损耗低0.0016。满足了中国工程物理研究院新型高梯度脉冲加速器研制的需求。.已发表论文5篇，另加1篇，接受，参会文章3篇；申请中国发明专利3项，美国专利1项。