ZrO_2添加对BaO-La_2O_3-TiO_2介质陶瓷介电性能的影响

Effects of ZrO_2 on Dielectric Properties of BaO-La_2O_3-TiO_2 Microwave Dielectric Ceramics

BaO-La2O3-TiO2(BLT)是典型的高介电常数微波介质陶瓷,其作为微波谐振器与滤波器的关键材料,在微波通讯技术上有着重要的应用。选用ZrO2对BLT进行改性研究,当ZrO2的加入量z<0.5mol时,烧结体的主晶相为Ba6-3xLa8+2x(Ti1-zZrz)18O54(x=1/2)钨青铜结构(TB)固溶体,随ZrO2加入量的增多,烧结体中产生第二相,当z=1.0mol时,烧结体的主晶相为La2Zr2O7和BaZrO3,这与结构许容因子的变化密切相关,获得较优介电性能如下:εr=103.71,Q.f=4862.53 GHz,τf=168.97×10-6/℃,优于不添加ZrO2时烧结体介电性能(εr=139.73,Q.f=1238.96 GHz,τf=179.97×10-6/℃),说明少量ZrO2的加入可以改善BLT陶瓷的品质因数和频率温度系数,略降低介电常数。SEM分析表明,少量ZrO2的加入没有改变烧结体的微观形貌,改性前后烧结体内部均为典型的柱状TB固溶体形貌。

BaO-La2O3-TiO2（BLT） is a typical kind of microwave dielectric ceramics with high dielectric constant, which is widely used in microwave resonators and filters. The effects of ZrO2 on the microwave dielectric properties of BLT ceramics were investigated. The Ba4.5La9Ti18O54 based tungsten-bronze phase became unstable for ZrO2 content z ≥ 0.5 mol, since La2Zr2O7 and BaZrO3 phases appeared. When z = 1.0 tool, these phases became the major phases. It led to the decrease of the tolerance factor. A small amount ofZr substitution for Ti improved the temperature coefficient of resonant frequency（τf） and the quality factor （Q·f）, but the dielectric constant（εr） decreased. The excellent microwave dielectric properties were achie- ved in BLT ceramics with z =0.1 mol： εr= 103.71, Q·f = 4862.53 GHz, τf = 168.97 × 10^-6/℃, which were better than the case of z = 0 mol （εr = 139.73, Q·f= 1238.96 GHz, τf = 179.97 × 10^-6/℃）. The SEM micrographs showed that a small amount of ZrO2 did not change the typical columnar grain morphology.