Microwave dielectric properties of (1 - x)Mg(Sn_(0.05)Ti_(0.95))O_3-x (Ca_(0.8)Sr_(0.2))TiO_3-y wt% ZnNb_2O_6 ceramics with near-zero temperature coefficient

摘要

The microstructures and the microwave dielectric properties of (1 - x)Mg(Sn_(0.05)Ti_(0.95))O_3-x(Ca_(0.8)Sr_(0.2))-TiO_3-y wt% ZnNb_2O_6 (x = 0.05-0.08, y = 2-8) ceramics system prepared by conventional solid-state route were investigated. The crystalline phases and the microstructures of the ceramics were characterized by means of X-ray diffraction and scanning electron microscopy. Zn~(2+) partially replaced Mg~(2+) in Mg(Sn_(0.05)Ti_(0.95))O_3 and formed the ilmenite-type (Mg_(1-δ)Zn_δ)(Sn_(0.05)Ti_(0.95))O_3 phase. Second phase (Mg_(1-δ)Zn_δ)(Sn_(0.05)Ti_(0.95))_2O_5 increased remarkably when excess ZnNb_2O_6 added. ZnNb_2O_6 as additives could not only effectively lower the sintering temperature of the ceramics to 1320 ℃, but also promote the densification. The microwave dielectric properties of specimens were strongly related to ZnNb_2O_6 and (Ca_(0.8)Sr_(0.2))TiO_3 content. The optimized microwave dielectric properties with ε_r ～ 22.13, Q × f value ～ 60,613(at 7 GHz) and τ_f value ～0.4 ppm/℃ were achieved for (1 - x)Mg(Sn_(0.05)Ti_(0.95))O_3-x(Ca_(0.8)Sr_(0.2))-TiO_3-y wt% ZnNb_2O_6 (x = 0.07, y = 4) sintered at 1320℃ for 2 h.