Enhanced dielectric properties of Mg4Nb2O9 ceramic by Ti substitution

In this paper, the strategy of substituting Ti 4+ for Nb 5+ in Mg 4 Nb 2 O 9 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 Mg 4 Nb 2− x Ti x O 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 Mg 4 Nb 2 O 9 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 BO 6 octahedral distortions. Ultimately, the Mg 4 Nb 1.85 Ti 0.15 O 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.