Effects of annealing atmospheres on microwave dielectric properties of Ba[(Mg1−xCox)1/3Nb2/3]O3 ceramics

• Effects of annealing on dielectric properties were determined for Ba[(Mg,Co)1/3Nb2/3]O3.
• Different effects of annealing atmosphere were indicated for different composition.
• The chemical bonding state played the important role on Q × f value.

Effects of annealing atmospheres (air, O2 and N2) on microwave dielectric properties have been determined for Ba[(Mg1−xCox)1/3Nb2/3]O3 ceramics. The ordering degree and ordering domain of x = 0.2 change very little after annealing, while those of x = 0.6 and x = 1.0 increase significantly. Annealing in all atmospheres leads to decrease in Q × f value for x = 0.2, and increase for x = 0.4–1.0. For x = 0.4–1.0, N2 annealing results in the best improvement in Q × f values, and it is next by air annealing and finally O2 annealing. ϵr and τf show little change by annealing and no obvious dependence on the annealing atmosphere for all compositions except x = 1.0 where the τf undergoes an obvious negative shift. The increase of Q × f values for x = 0.4–1.0 after annealing can be interpreted by the increased ordering degree that is accompanied by the domain growth. The different chemical bonding states in samples annealed in different atmospheres may contribute to the different Q × f values.

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