【作者】 李赛；

【导师】 李玲霞；

【作者基本信息】 天津大学 ， 微电子学与固体电子学， 2016， 硕士

【摘要】 MgO-TiO₂体系微波介质陶瓷材料具有优异的品质因数,且原料丰富、价格低廉,因而广受关注。本课题针对MgO-TiO₂体系普遍存在的缺点,通过离子取代、两相复合、添加剂改性、添加烧结助剂等手段,改善体系的烧结特性,从而改善整体的微波介电性能。具体研究内容及结论如下:首先,对原有的MgTiO₃-CaTiO₃体系进行了改进:研究了Zn²⁺取代和LaAlO₃对MgTiO₃-CaTiO3体系的结构与性能的影响。结果表明:陶瓷样品的介电性能尤其是Q×f值相较于95MCT有了显著的提高。在1200℃下烧结时,样品的介电性能优异且温度系数近零:?r²2.5,Q×f⁸9,000GHz,τf^-6.9×10-6/℃。为降低95MCT-1.0mol%LaAlO3体系的烧结温度,选取了B2O3作为烧结助剂。得到以下结论:B2O3的加入显著降低了体系的致密烧结温度;当B2O3添加量达到2.0wt%时,陶瓷样品中出现了CaLa4Ti4O15相,此时陶瓷样品介电性能由致密度和物相组成共同决定。其中,影响Q×f值的主导因素随着B2O3添加量不同而不同。添加3.0wt%B2O3的陶瓷样品在1125℃下烧结时,具有最佳的介电性能:?r²0.3,Q×f⁵7,000GHz,τf^-7.2×10-6/℃。其次,对具有近零温度系数的新陶瓷体系进行了研究。将CaTiO3和（Na0.5La0.5）TiO3按照一定比例混合反应生成单相的固溶体（Ca0.8Na0.1La0.1）TiO3（CNLT）,然后调节Mg0.95Zn0.05TiO3（MZT）的温度系数至近零。得出以下结果:（1-x）MZT-xCNLT陶瓷样品的物相由主晶向MZT和次晶向CNLT组成。样品的介电性能和烧结温度以及x的值密切相关。在x=0.07,1225℃下烧结的陶瓷样品可以获得最佳的微波介电性能:?r²2.5,Q×f⁷9,300GHz,τf⁰×10-6/℃。然后用CNLT调节Mg1.8Ti1.1O4的温度系数至近零。得出以下结论:体系的介电性能与烧结温度密切相关。在1300℃下烧结的陶瓷样品可以获得最佳介电性能:?r¹9.7,Q×f⁶8,000GHz,τf^-0.7×10-6/℃。更多还原

【Abstract】 The MgO-TiO₂ microwave dielectric materials has attracted much attention since its low dielectric loss,abundant raw materials source and low cost.On account of the common defects of MgO-TiO₂ microwave dielectric materials,the sintering characteristic and microwave dielectric properties of the MgO-TiO₂ system have been improved through the methods such as two phase composite,ion doping,adding sintering additives.The main study and conclusion included as follows:Firstly,the original MgTiO₃-CaTiO₃ system was improved:The microstructures and microwave dielectric properties of 1.0mol% LaAlO3 doped 0.95（Mg0.95Zn0.05）TiO3–0.05CaTiO₃ ceramics were investigated.As a result,dielectric properties of the ceramic system is much higher than that of MgTiO₃-CaTiO₃ system.The optimized microwave dielectric properties with er 22.5,Q×f value 89000 GHz and a tf of ^-6.9×10-6/°C were achieved for samples sintered at 1200°C.To lower the the sintering temperature of 95MCT-1.0mol% LaAlO₃ ceramic system,B2O3 was chosen as the sintering aid.It was concluded that B₂O₃ could effectively lowered the sintering temperature of the ceramic system.With more than 2wt% B₂O₃ addition,the secondary phase CaLa4Ti₄O₁₅ was formed.The microwave dielectric properties of the ceramic system were strongly correlate with the densification as well as the phase composition.The dominant factor affecting Q×f value varied with increasing B₂O₃ addition.With 3wt% B₂O₃ addition,a maximum Q×f of 57000GHz（at 8GHz）,with a dielectric constant of 20.3 and a tf of-7.2×10-6/°C were obtained for samples sintered at 1125°C.Secondly,new microwave dielectric ceramic systems were investigated.CaTiO₃ and（Na0.5La0.5）TiO₃ could form solid solution(Ca_0.8Na_0.1La_0.1)TiO₃（CNLT）with a proper ratio.Then CNLT was used to adjust the tf value of MZT to zero.It was concluded that（1–x）MZT–xCNLT ceramic system showed a mixture of the trigonal structured MZT as a main phase,the pure orthorhombic perovskite structured CNLT as a minor phase.The microwave dielectric properties of the ceramic system were strongly correlate with the sintering temperature as well as the x value.A fine combination of microwave dielectric properties（er 22.5,Q×f ⁷9300GHz and tf 0×10-6/°C）was achieved for 93 MZTCNLT ceramics sintered at 1225°C.Moreover,CNLT was used to adjust the tf value of Mg1.8Ti1.1O4 to zero.The microwave dielectric properties of the ceramic system were strongly correlate with the sintering temperature.0.93Mg1.8Ti1.1O4-0.07 CNLT ceramic samples sintered at 1225°C showed excellent microwave dielectric properties with ?r 19.7,Q×f 68,000 GHz,τf ^-0.7×10-6/°C更多还原