Effect of small amount of cobalt substitution on structure and microwave dielectric properties of barium magnesium niobate ceramics

We investigated effects of substituting cobalt for magnesium on microstructures and microwave dielectric properties of BaMg1/3Nb2/3O3 ceramics. Nucleation and growth of 1:2 ordered domains dominate microstructural variations for Ba(Mg1−xCox)1/3Nb2/3O3 ceramics. Microstructures such as grains sizes and domain sizes significantly dominate variations of Q × f value. Less ordered domains are nucleated when substituting small amount of cobalt (x < 0.1). Accordingly, domains and grains significantly grow with increased cobalt substitution. The 1:2 ordering degree is subsequently increased, and Q × f achieves a maximum value at x = 0.05. Nevertheless, while cobalt substitution exceeds x = 0.1, more ordered nuclei occur and consequently affect the domain growth and the grain growth. The Q × f value remarkably decreases at x = 0.1, and varies due to different ordering degrees and compositions. The Q × f value of specimens at x = 0.05 becomes as high as 43,000, and is similar to that of specimens at x = 0.5.