Enhanced dielectric properties of Mg₄Nb₂O₉ ceramic by Ti substitution

In this paper, the strategy of substituting Ti⁴⁺ for Nb⁵⁺ in Mg₄Nb₂O₉ microwave dielectric ceramic was employed to improve the microwave dielectric properties. Specifically, a maximum Q × f value of 137,462 GHz was obtained at x = 0.15, resulting in a nearly 30% increase in the quality factor (Q × f) for the Mg₄Nb_2−xTi_xO_9−x/2 sample. Moreover, we investigated the phase composition, micromorphology, and the relationship between structural characterization and dielectric properties. The X-ray diffraction (XRD) patterns indicated that only a single Mg₄Nb₂O₉ phase with a trigonal corundum-type structure was formed in all the samples. The ɛ_r was related to the ionic polarizability, and the τ_f value was dependent on the B–O bond valence (V_B–O) and BO₆ octahedral distortions. Ultimately, the Mg₄Nb_1.85Ti_0.15O_8.925 ceramic sample exhibited microwave dielectric properties with ɛ_r = 13.89, Q × f = 137,462 GHz, and τ_f = − 55.1 ppm/°C.