低介电常数堇青石陶瓷的微结构调控与微波介电性能研究

Low dielectric constant silicate ceramics have a broad application prospect for microwave communication techniques, and are a new research direction in the fields of microwave dielectric ceramics. But, there still are some questions needed to research in the silicate materials, such as physical relating mechanism between silicate microstructures (Si/Al atomic arranging orders and crystal lattice atoms motion, etc) and microwave dielectric properties, and the mutual harmonization of three microwave dielectric characteristic parameters (dielectric constants, quality factors, and temperature coefficients of resonant frequency). In order to investigate these questions, the project selects cordierite as research objects, and uses elements doping and traditional ceramic sintering and special SPS/HP ceramic sintering methods prepare (Mg1-xAx)2(Al1-yBy)4Si5O18 cordierite ceramics. As followed, the project will research the physical rules between cordierite microstructures and microwave dielectric properties. Based on these rules, the projects will control cordierite ceramic microstructures, and research the technique mechanism of mutual hominization about three microwave dielectric characterictic parameters. If the projec had been done, the achievements would be beneficial to enrich the knowledge of physical theory about silicate microwave dielectric properties, and develop a family of low dielectric constant microwave dielectric ceramics. So, it is am importance for both the research of natural sicence and the development of social economies.

低介电常数硅酸盐陶瓷材料，在微波毫米波通信系统中具有广泛的应用前景，是近年国际微波介质陶瓷研究领域内的一个新兴方向。但是，在硅酸盐结构中，硅铝原子排列的有序性和晶格原子基元运动等微结构特征与微波介电性能的物性关联规律及其微波介电性能三参数(介电常数、品质因数与谐振频率温度系数)相互协调的机制问题尚未研究清楚。项目针对以上问题，经过筛选并选取堇青石为研究对象，提出采用元素掺杂，常压、SPS与HP烧结,制备(Mg1-xMx)2Al4Si5O18堇青石陶瓷(M=掺杂元素)；研究(Mg1-xMx)2Al4Si5O18堇青石陶瓷各微结构特征与微波介电性能的物性关联规律；并在此基础上，控制堇青石微结构，研究其微波介电性能三参数相互协调的工艺机制。本项目的开展将有助于丰富硅酸盐微波介电性能的物性认识与低介电常数微波介质陶瓷材料的种类，具有重要的自然科学研究内容与社会经济价值。

低介电常数硅酸盐陶瓷作为微波介质功能器件在微波通信系统中具有广泛的应用。本项目以堇青石（Mg2Al4Si5O18）为原型，从不同角度调控[(Si4Al2)O18]四面体六元环，研究[(Si4Al2)O18]六元环结构变化和晶体结构基元运动的微结构特征与微波性能的物性关联规律及其微波介电性能三参数(er，Qf，tf)相互协调机制。1. 采用Ti4+离子掺杂修饰[(Si4Al2)O18]六元环制备Mg2Al2Al2-xTixSi5O18(0≤x≤0.35)堇青石型陶瓷， x=0.1得到最佳Qf值：69，800 GHz（17.6 GHz），er = 6.34, tf= -21 ppm/℃；x= 0.25获得近零温度系数：tf = -0.02 ppm/℃, er = 6.77，Qf = 47，600 GHz （18.4 GHz）；2. 采用La3+、Sm3+取代置换修饰[Mg6O36]八面体六元环制备(Mg1–xLnx)2Al4Si5O18（Ln = La，Sm，0≤x≤0.35）堇青石型陶瓷，由于[(Mg1-xLnx)6O36]八面体与[(Si4Al2)O18]四面体六元环相互作用，促进[(Si4Al2)O18]四面体六元环对称性提高。(Mg1–xLax)2Al4Si5O18（x= 0.05）获得最佳微波介电性能：Qf = 78，500 GHz（14.3 GHz）, Er= 6.7，tf = -22 ppm/℃；(Mg1–xSmx)2Al4Si5O18（x= 0.20）陶瓷获得较好微波介电性能: er= 6.8，Qf = 24，800 GHz（13.2 GHz），tf = -17ppm/℃。3. 采用Ca2+/Sr2+/Ti4+掺杂同时修饰[(Si4Al2)O18]四面体与[Mg6O36]八面体六元环制备Mg2-xRexAl2Al2-yTiySi5O18(Re = Ca，Sr，0≤x≤0.35) 堇青石型陶瓷，x=0.1得到最佳Qf = 80，600 GHz（13.6 GHz），er= 6.53，tf = -18 ppm/℃。总结研究结果得出：1.硅铝原子有序排列的[(Si4Al2)O18]六元环对称性对堇青石型陶瓷的品质因数(Qf值)提高具有关键性的影响；2.堇青石型陶瓷微波性能三参数(er,Qf，tf)可以通过工艺优化实现协调，获得具有应用前景的微波功能器件。

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