Ionic modification effects on crystal structure and microwave dielectric properties of MgTiTa2O8 ceramics

In this study, two ionic modification strategies on trirutile MgTiTa2O8 ceramics, including Mg site non-stoichiometry (Mg1+xTiTa2O8) and (Al1/2Nb1/2)(4+) ionic doping (MgTi1-y(Al1/2Nb1/2)(y)Ta2O8), were adopted to improve the microwave dielectric properties. The results show that a small doping content does not change the crystal structure type, indicating that the trirutile MgTiTa2O8 solid solutions can be formed. On the one hand, the increase of sintering decreases the porosities of microstructures, which benefit the dielectric constant and Qxf value; however, excessive sintering temperature leads to abnormal growth of grain, deteriorating the uniformity of grain growth and then increases the dielectric loss. On the other hand, the variations of the dielectric constant are dominated by the ionic polarizability intrinsically, while the Qxf value is positively correlated with the packing fraction value. The two modification strategies both benefit the Qxf value with improvements of about 21% and 30% in Mg1+xTiTa2O8 and MgTi1-y(Al1/2Nb1/2)(y)Ta2O8 ceramics, respectively. In summary, excellent microwave dielectric properties of MgTi1-y(Al1/2Nb1/2)(y)Ta2O8 (y = 0.10) system are obtained when sintered at 1350 & DEG;C: & epsilon;(r) = 43.58, Qxf = 24,565 GHz, & tau;(f) = 100.37 ppm/& DEG;C.