Ca_(3–x)Mg_(x)Yb_(2)Ge_(3)O_(12)(0≤x≤3)石榴石的A位Rattling效应与微波介电性能

Rattling Effect in A Site and Microwave Dielectric Properties of Ca_(3-x)Mg_(x)Yb_(2)Ge_(3)O_(12)(0≤x≤3)Garnets

微波介质陶瓷是5G/6G通讯技术的关键基础材料,具有高品质因数(Q×f)、低介电常数(εr)以及近零谐振频率温度系数(τf)的材料已逐渐成为研究与开发的重点。通过固相反应法制备了系列Ca_(3-x)Mg_(x)Yb_(2)Ge_(3)O_(12)(0≤x≤3)石榴石陶瓷。当0≤x≤2时,样品为正石榴石结构,相对介电常数εr逐渐从10.3增加至11.8,品质因数Q×f值逐渐从98000 GHz降低到78000 GHz,谐振频率温度系数τf在(-40~-56)×10^(–6)/℃之间波动。当2<x≤3时,Mg^(2+)进入A位,εr迅速增大(~13.5),Q×f值显著降低(~19800 GHz),τf值则从负急剧转变为正(+70.5×10^(–6)/℃),可归之于A位Mg^(2+)的Rattling效应以及Mg^(2+)与Yb^(3+)失配的缘故.根据远红外反射谱拟合外推了Ca_(3-x)Mg_(x)Yb_(2)Ge_(3)O_(12)(0≤x≤3)陶瓷微波频段的本征εr和Q×f值,与实际测量值相符合.

Microwave dielectric ceramics are the key basic materials of 5G/6G communication technology,and the materials with a high quality factor(Qxf),a low dielectric constant(er)and a near-zero temperature coefficient of resonant frequency(t)become a focus of research and development.In this paper,a series of garnet Ca_(3-x)Mg_(x)Yb_(2)Ge_(3)O_(12)(0≤x≤3)ceramics were prepared by a solid-state reaction approach,and the influence of Mg+“rattling"effects in the A-site on the microwave dielectric properties was investigated.The ceramics with 0≤x≤2 exhibit a normal garnet structure,&r gradually increases from 10.3 to 11.8,whereas the Qxf gradually decreases from 98000 GHz to 78000 GHz,and t is in the range from(-40~-56)×10^(-6)/C.The ceramics with 2<x≤3 have an inverse garnet structure with Mg^(2+)in the A-site and er quickly increases to 13.5,whereas the Qxf apparently decreases to 19,800 GHz,and the tr value varies from the negative value to the positive value(+70.5×10^(-6)/℃),which are attributed to the rattling effect Mg*and the mismatch between Mg^(2+)and Yb^(3+)in the A-site.According to the extrapolated values of the far-infrared reflective spectrum in the microwave region,the intrinsic er and Qxf values are in a reasonable agreement with the measured values.