Microwave dielectric properties of low-loss (Zn1-xCox)3Nb2O8 ceramics for LTCC applications

The phase relation, crystal structure and microwave dielectric properties of (Zn1-xCox)(3)Nb2O8 ceramics were investigated. The limit of (Zn1-xCox)(3)Nb2O8 solid solutions was approximately x = 0.4. With an increasing x, the corrected dielectric constant decreased and the temperature coefficient of resonant frequency (tau(f)) increased. The tau(f) value is strongly dependent on the tilting of the oxygen octahedral, which can be evaluated by the B-site bond valence. However, a tremendous loss reduction can be achieved by a small amount of Co substitution due to the increase in relative density and packing fraction. The B2O3 and CuO addition can effectively lower the sintering temperature of (Zn0.95Co0.05)(3)Nb2O8 without seriously deteriorating the dielectric properties. For LTCC applications, the 4 wt% B2O3-CuO doped (Zn0.95Co0.05)(3)Nb2O8 ceramic sintered at 930 degrees C is a good choices because of its excellent dielectric properties (epsilon(r) similar to 20.75, Q x f similar to 105,000 GHz and tau(f) similar to -83.7 ppm/degrees C) and the chemical compatibility with silver. (C) 2014 Elsevier B.V. All rights reserved.