非低熔点复合氧化物助烧的LTCC介质材料及其烧结机理研究

Low temperature cofired ceramics (LTCC) technology is one of the most important way for fabricating miniaturized, integrated, and multifunctional devices. The development of emerging wireless communication and information electronic system demands high performance LTCC dielectric materials with ultra-low dielectric loss, high mechanical strength and high thermal conductivity. This project proposed to develop this kind of high performance LTCC materials using high performance microwave dielectrics like alumina, magnesium titanate as matrix and oxide composite without low melting point compounds as sintering aid. High throughput experimental method will be used to screen and optimize the composition of the oxide composite sintering aids. The phase composition, reactivity with matrix, and the eutectic point with matrix of the oxide composite sintering aids will be investigated to find the scientific theme of sintering aid selection. The low temperature sintering mechanism will be studied by the grain boundary phase and composition analysis, interface microstructure analysis of the natural cooled samples and quenched samples from high temperature. The effects of grain size and sintering atmosphere will also be investigated. The low temperature sintering mechanism and the scientific evidence of oxide composite sintering aid selection would be clarified through the profound investigation of this project, which would promote the development of LTCC dielectric materials with excellent dielectric, mechanical and thermal performance.

低温共烧陶瓷(LTCC)技术是实现电子元器件小型化、集成化和多功能化的重要技术途径，具有优良介电、力学和热学综合性能的LTCC介质材料是更高工作频率、更小尺寸和更高集成密度的电子器件开发的迫切需求。本项目提出采用非低熔点复合氧化物助烧剂来降低微波介质材料的烧结温度，从而获得高性能LTCC介质材料。将以氧化铝和钛酸镁两种具有代表性的材料为基质，采用高通量实验技术来优化复合氧化物烧结助剂的组成；通过复合氧化物助烧剂的物相分析、与基质材料的反应特性及低共熔特性分析探索优良助烧剂选择的科学依据；通过晶界相及成分、界面微结构等分析研究助烧剂作用下的低温烧结机理；通过不同粒径及不同气氛条件下材料烧结特性分析研究影响烧结动力学的因素，阐明通过非低熔点复合氧化物助烧来获得高性能LTCC介质材料的烧结机理及助烧剂选择依据，为研制具有优良介电、力学和热学综合性能的LTCC介质材料奠定科学和技术基础。

针对LTCC材料低温烧结与优良性能难于保持的矛盾问题，本项目提出采用非低熔点氧化物助烧来实现低温烧结的思路，主要研究内容包括低温烧结复合氧化物助烧剂的选择和优化、低温烧结机理研究、影响复合氧化物助烧效果的因素及材料结构性能关系研究。项目研究中以CuO-Nb2O5-TiO2复合氧化物体系为基础，系统研究了该复合氧化物体系对Al2O3、ZnAl2O4、ZrO2、MgO等材料的助烧效果，发现了系列新的烧结现象，结合高分辨投射电镜、电学、力学、热学性能综合表征，阐明了界面纳米非晶膜（界面皮相）对促进活化烧结的作用，研制出了电-热-力综合性能优良的CuO-Nb2O5-TiO2+Al2O3体系LTCC新材料，介电常数12.6，Q׃~7400 GHz，抗折强度~320 MPa，热导率~18.64 W/m·K。探索了4Cu-Fe-4Nb、4Cu-Ni-4Nb、4Cu-Mn-4Nb、4Cu-Ti-4Mn等三元复合氧化物体系的助烧效果，发现Cu离子在助烧中起关键作用。作为项目的拓展研究，把机器学习方法引入到新型LTCC微波介质材料预测，获得了低熔点微波介质材料预测模型，预测设计了系列低本征烧结温度的新材料。在本项目的资助下，正式发表科研论文7篇，申请发明专利2项（其中1项已授权）；培养硕士、博士研究生5名。本项目圆满完成了预定研究任务，项目研究成果不仅有重要的应用价值，对高性能LTCC介质材料开发有重要的指导和借鉴意义。