Structure and microwave dielectric properties of Ba[(Mg 1−x Ni x ) 1/3 Nb 2/3 ]O 3 ceramics

Abstract The microwave dielectric characteristics of Ba[(Mg1−xNix)1/3Nb2/3]O3 ceramics have been investigated together with the microstructures. The microwave dielectric properties are deeply linked to the cations ordering, ordering domain, and Ni valence state. Ni-substitution for Mg promotes the homogenous nucleation of ordering domains but does not favor the domain growth, resulting in the decrease of domain size and ordering degree. τf is adjusted from positive to negative by Ni-substitution, a near-zero τf is obtained for x = 0.6; ϵr decreases slightly with increasing x. The ordering degree and ordering domain size dominates the variations of Q × f values. After post-densification annealing, Q × f values increase significantly, while the ϵr and τf values undergo a negative shift. The Ni volatilization results in the oxidization of Ni2+ to Ni3+, affecting the cations ordering and microwave dielectric properties. The best combination of microwave dielectric properties is obtained for the composition with x = 0.6: ϵr = 29.5, Q × f = 60,400 GHz, τf = 2.8 ppm/°C.