Investigation of phase composition and microwave dielectric properties of MgO‐Ta2O5 ceramics with ultrahigh Qf value

Four MgO‐Ta₂O₅ ceramics with the MgO/Ta₂O₅ mole ratio x = 1, 2, 3, and 4 were prepared by traditional solid‐state reaction method, and the influence of x on the phase composition, microstructure, and dielectric properties (the dielectric constant ε_r, the temperature coefficient of resonant frequency τ_f and the quality factor Qf) of the materials was investigated using XRD, SEM, etc. The results indicated that the ceramics were composed of two crystalline phases MgTa₂O₆ and Mg₄Ta₂O₉ in the composition range studied, and that the dielectric properties ln ε, 1/Qf, and τ_f changed proportionally to the fraction of main crystal phases, which meet perfectly with the mixing model proposed in this study. It is obvious that the proportion of the two crystal phases could be precisely controlled by x, and thereby, the dielectric properties can be conveniently and precisely tailored. Our research provided a new microwave dielectric ceramic with the composition of 2MgO‐Ta₂O₅, which has an ultrahigh Qf value (211 000 GHz), low dielectric constant ε_r (19.9), and near zero temperature coefficient of resonant frequency τ_f (8 ppm/°C).