r(Nd)/r(Bi)对Ba0.75Sr0.25(NdxBi1-x)2Ti4O12微波陶瓷性能的影响

BaR2Ti4O12(R为稀土元素)系固溶体有很好的微波介电性能,尤其是Nd系材料有很高的介电常数(εr)和高品质因数(Q×f),该文研究了不同Nd/Bi比对Ba0.75Sr0.25(NdxBi1-x)2Ti4O12微波介质陶瓷结构性能的影响。当x=0.75时,即摩尔比x∶(1-x)=3∶1时(缩写为B13)有很好的介电性能:εr=118.5,Q×f=4 607(f=2.8GHz),谐振频率温度系数τf=-1.3×10-6℃-1。对不同Nd/Bi比的样品在1 250℃到1 400℃烧结3h后的陶瓷进行XRD分析后发现,陶瓷主相为BaNd2Ti4O12,有少量第二相Ba2Ti9O20。对Bi含量逐渐增加的陶瓷样品进行微观分析可知,Bi有助于致密度的提高和晶粒的增长,随着Nd/Bi比的减小,εr慢慢增大,τf渐渐趋向于0并向负方向移动,但同时降低了Q×f值。

Effect of Molar Ratio of Nd/Bi on the Microwave Ceramic Properties of Ba0.75 Sr0.25 ( Ndx Bi1- x ) 2 Ti4 O12 Microwave Materials

BaR2Ti4O12(R denotes the rare earth)series solid solutions have excellent microwave dieletric properties.In particular,Nd-system materials have high dielectric constant(εr) and high quality factor(Q×f).This work investigated the influence of different molar ratio of Nd/Bi on the structural properties of the microwave dielectric ceramics of Ba0.75Sr0.25(NdxBi1-x)2Ti4O12.When x=0.75,that is,the molar ratio of x∶(1-x)=3∶1(abbreviated as B13),this material shows excellent dielectric properties with εr=118.5,Q×f=4 607(f=2.8 GHz),and the temperature coefficient of resonant frequency τf=-1.3×10-6℃-1.XRD patterns show that the main crystal phase of all the ceramics with different Nd/Bi ratio sintered at 1 250 ℃ to 1 400 ℃ for 3 h has main BaNd2Ti4O12 with small amount of second phase Ba2Ti9O20.SEM photographs suggest that Bi working as sintering aids promote the densification and grain growth of the ceramic samples.With the decrease of Nd/Bi ratio,εr increased slowly τf approached to zero gradually and moved to the negative direction while the Q×f value decreased.