(Ti0.5W0.5)^5+离子掺杂对NdNbO4微波介质陶瓷性能影响

(Ti0.5W0.5)^5+ Cations Doping on Properties of NdNbO4 Microwave Dielectric Ceramics

稀土离子被广泛应用于提高微波介质陶瓷的性能。稀土铌酸盐近年来被广泛研究,尤其是关于NdNbO4的单个离子掺杂改性。采用固相烧结法制备NdNb1-x(Ti0.5W0.5)xO4(x=0.05,0.1,0.2,0.3),结果表明x大于0.1时的陶瓷体系中两相共存,主晶相为褐钇铌矿结构的NdNbO4相,第二相为易解石结构的NdTiNbO6相。随着x的增大,相对介电常数与密度的变化趋势一致;品质因数与谐振频率的乘积(Q×f)先增大后减小,增大是由密度的变化引起的。当x=0.3时,由于第二相的含量增多、晶界数量增多,Q×f出现下降趋势。当x=0.2,在1 225℃时,气孔未排尽;在1 275℃时烧结致密且得到的陶瓷微波介电性能较好:相对介电常数εr为19.83,Q×f为44 711 GHz,谐振频率温度系数τf为-2.057×10^-5/℃;而温度升至1 300℃时,由于晶粒异常长大导致气孔出现,陶瓷性能降低。

Rare earth cations are extensively applied for improving properties for microwave dielectric ceramics.The rare earth niobate has been widely studied in recent years,especially for single ion doping modification of NdNbO4.NdNb1-x(Ti0.5 W0.5)xO4(x=0.05,0.1,0.2,0.3)ceramics were prepared via the solid-state sintering method.The results show that two phases are observed in the ceramic system when xis larger than 0.1,the main crystal phase is NdNbO4 phase with fergusonite structure,and the second phase is NdTiNbO6 phase with aeschynite structure.With the increase of x,the variation trend of the relative dielectric constant is consistent with the density.The product of quality factor and resonance frequency(Q×f)firstly increases caused by the variation of the density,and then decreases.While at x=0.3,because the second phase content and the number of grain boundary increase,Q×fshows a decline tendency.While at x=0.2,there are still some pores in the ceramic at 1 225℃,and the obtained microwave dielectric properties of the ceramic are more excellent at 1 275℃:the relative dielectric constantεris19.83,Q ×f is 44 711 GHz,and the temperature coefficient of resonance frequencyτfis-2.057×10^-5/℃.However,when the temperature rises to 1 300 ℃,the abnormal growth of the grains leads to pores and then degrades the ceramic properties.