Li2O-B2O3复合掺杂对BaAl2Si2O8陶瓷结构与介电性能的影响

采用传统固相反应工艺,按质量分数合成BaO-Al2O3-SiO2-5%(xLi2O-yB2O3)(x=0. 2~0. 6,y=0. 8~0. 4)陶瓷。研究xL-yB烧结助剂对BAS系微波介质陶瓷的结构和介电性能的影响。通过Clausius-Mossotti公式计算讨论了BAS理论与实验介电常数的差异。研究结果表明:xL-yB烧结助剂中Li+进入钡长石Ba2+位,并产生了O2-空位,促进BAS六方相向单斜相转变。添加适当比例的xL-yB烧结助剂后,BAS陶瓷的烧结温度从1400℃降低到925℃,同时BAS陶瓷样品密度、品质因数(Q×f)值以及谐振频率温度系数(τf)得到改善。当烧结助剂为0. 5L-0. 5B,烧结温度为925℃时,可获得综合性能相对较好的BAS陶瓷,其介电性能:εr=6. 74,Q×f=26670 GHz,τf=-21. 09×10-6℃-1。

Effect of Li_2O-B_2O_3 sintering aids on structure and dielectric properties of BaAl_2Si_2O_8 ceramics

BaO-Al2O3-SiO2-5%( xLi2O-yB2O3)( x = 0. 2-0. 6,y = 0. 8-0. 4) ceramics were prepared by solid state route.The work studied the effect of xL-yB sintering aids on the microstructure and dielectric properties of BAS system ceramics. Deviation was discussed between theoretical and experimental relative permittivity of BAS ceramics. The results shows that xL-yB sintering aids can reduce the sintering temperature from 1400 ℃ to 925 ℃,and the O2-vacancy is formed by substituting Ba2+ with Li+ to promote the transformation of BAS from hexagonal phase to monoclinic phase. The density,Q × f value,and temperature coefficient at resonant frequency( τf) of BAS-5%( xL-yB) ceramics are improved by adding proper proportion of the xL-yB sintering aids. The BAS-5%( 0. 5 L-0. 5 B) sintered at 925 ℃ obtains good microwave dielectric properties as follow: ε r = 6. 74,Q×f = 26670 GHz,τf =-21. 09×10-6℃-1. The composite shows good potential for practical LTCC applications.