Correlations between structure and microwave dielectric properties of Co doped MgMoO4 ceramics

Mg1-xCoMoO4 (x = 0.01-0.15) ceramics were prepared by traditional solid-state methods. The phase composition, crystalline structure, micromorphology, and microwave dielectric properties of Mg1-xCoMoO4 ceramics were comprehensively studied. Mg1-xCoMoO4 ceramics present monoclinic wolframite structures from x = 0.01 to x = 0.15 with Co occupying the Mg-site. With the addition of Co2+, epsilon(r) of Mg1-xCoMoO4 ceramics increase. Q x f is maximal at 5 mol% Co2+ content. The Mg0.95Co0.05MoO4 ceramic exhibits an optimal microwave dielectric property: epsilon(r )= 7, Q x f = 59247 GHz, tau(f) = - 68 ppm/degrees C. The Q x f values increase by 20% compared with the pure MgMoO4 ceramics (similar to 49149 GHz). Doping Co2+ effectively promotes the densification of ceramics and increases epsilon(r) and Q x f. However, when the Co content exceeds 5 mol%, the decreased packing fraction and disorder distribution of ions contribute to the increase in dielectric losses. The correlations between Co2+ substitution and wolframite structure have been discussed by Raman spectroscopy, FT-IR spectroscopy and Rietveld refinement.