Microwave dielectric properties of the (1-x)Mg2TiO4-xCaTiO3-y wt.% ZnNb2O6 ceramics system

Composite ceramics based on (1 - x)Mg2TiO4-xCaTiO(3)-y wt.% ZnNb2O6 (x=0.12-0.16, y=0-8) were prepared by a conventional mixed-oxide route. Zn2+ partially replaced Mg2+ in Mg2TiO4 and formed the spinel-structured (Mg1-delta Zn delta)(2)TiO4 phase. Nb2+, is known to be solid soluble in CaTiO3, was found to change its shape from cubic to pliable. A bi-phase system (Mg1-delta Zn delta)(2)TiO4 and CaTiO3 exhibited in all samples, where a small amount of second phase Mg1-delta Zn delta TiO3 was also detected. The microwave dielectric properties of specimens were strongly related to ZnNb2O6 and CaTiO3 content. As y increased, epsilon(r) and tau(f) decreased, however, Q x f decreased to a minimum value and started to increase thereafter. It was also found that epsilon(r) and tau(f) increased and Q x f decreased with increasing x. The optimized microwave dielectric properties with epsilon(r) = 18.37, Q x f = 31,027 GHz (at 6 GHz), and tau(f) = 0.51 ppm/degrees C were achieved for (1 - x)Mg2TiO4-xCaTiO(3)-y wt.% ZnNb2O6 (x=0.12, y=4) sintered at 1360 degrees C for 6 h. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.