堇青石基化合物的结构调控和微波介电性能研究

发布时间：2018-06-25 10:53

  本文选题：堇青石 + 微波介质陶瓷　； 参考：《杭州电子科技大学》2015年硕士论文

【摘要】：本文主要以堇青石(Mg2Al4Si5O18)微波介质陶瓷为研究对象,针对堇青石陶瓷的烧结温度范围窄、烧结温度高、品质因数Qf低、谐振频率温度系数?f较大等问题,提出相应的解决方案。研究范畴包括:物相组成、烧结特性、微观形貌、晶格参数、Si/Al排列顺序、[(Si/Al)O4]四面体、以及[(Si4Al2)O18]六元环的结构变化对其微波介电性能的影响,并成功制备了性能良好的堇青石基微波介质材料。本文的具体内容如下:1)在(Mg1 xLax)2Al4Si5O18+x(0≤x≤0.35)陶瓷的改性研究中,La3+完全取代Mg2+离子形成堇青石基固溶体。在0≤x≤0.05时,外围[(Mg1-xLax)6O36]六元环结构畸变,对内[(Si4Al2)O18]六元环产生压缩应力,使[(Si4Al2)O18]六元环的对称性得到提高;然而,在0.05x≤0.10时,择优取代优势减弱,压缩应力趋于平衡。最终,(Mg1 xLax)2Al4Si5O18+x(x=0.05)陶瓷获得最佳微波介电性能:?r=6.7,Qf=56,500 GHz,?f=-20.5 ppm/℃。2)在(Mg1 x Yx)2Al4Si5O18+x(0≤x≤0.25)的改性研究中,Y3+的取代形成微量堇青石固溶体。在0x≤0.05时,陶瓷的相对介电常数有所增加。当0.1≤x≤0.25时,出现第二相Y2Si2O7,表现为Mg2Al4Si5O18/Y2Si2O7的复合相。在x=0.05时,(Mg1 xYx)2Al4Si5O18+x的微波介电性能为:?r=6.3,Qf=38,900 GHz,?f=-28ppm/℃。3)在(1-x)Mg2Al4Si5O18-xTiO2(0≤x≤0.35)陶瓷的改性研究中,在0≤x≤0.10时,陶瓷呈现堇青石固溶体。在0.10x≤0.35时,陶瓷呈现为Mg2Al4Si5O18/TiO2的复合相。(1-x)Mg2Al4Si5O18-xTiO2(x=0.10)堇青石基固溶体获得最佳品质因数:Qf=69,800 GHz,?r=6.34,?f=-21 ppm/℃;而(1-x)Mg2Al4Si5O18-xTiO2(x=0.25)复合陶瓷获得近零频率温度系数:?f=-0.02 ppm/℃,?r=6.77,Qf=47,600 GHz。4)在(1-x)Mg2Al4Si5O18-xSCTiO3(SC=Sr、Ca;0≤x≤0.35)陶瓷的改性研究中,在0≤x≤0.10时,形成堇青石固溶体;当0.15≤x≤0.35时,出现了液相SCAl2Si2O8长石,此外,还有少量钙钛矿结构的SCTiO3沉淀析出。最终,(1-x)Mg2Al4Si5O18-xSrTiO3(x=0.10)堇青石固溶体获得最优微波介电性能:εr=6.53,Qf=80,600 GHz,τf=-18 ppm/℃;液相CaAl2Si2O8拥有比SrAl2Si2O8更高的介电损耗。因此,(1-x)Mg2Al4Si5O18-xCaTiO3(x=0.05)堇青石固溶体微波介电性能为:εr=6.27,Qf=40,300 GHz,τf=-31 ppm/℃。
[Abstract]:In this paper, the microwave dielectric ceramics of cordierite (Mg2Al4Si5O18) are taken as the research object. The corresponding solutions are put forward for cordierite ceramics with narrow sintering temperature range, high sintering temperature, low quality factor QF and large resonant frequency temperature coefficient. The fields of study include: phase composition, sintering characteristics, micromorphology, lattice parameters and the order of arrangement of Si / Al, [(Si4Al2) O4] tetrahedron, and the effect of the structural changes of [(Si4Al2) O18] six-member ring on the microwave dielectric properties of [(Si4Al2) O18]. Cordierite based microwave dielectric materials with good properties were successfully prepared. The specific contents of this paper are as follows: 1) in the study of modification of (Mg1 X Lax) 2Al4Si5O18x (0 鈮，

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