Abstract
In this work, a series of (l-x)MgAl_2O_4-xMg_2TiO_4 (expressed as (l-x)MA- xMT) (0.0 < x < 0.9) ceramics were successfully prepared via a solid-state reaction, and the effect of Mg_2TiO_4 content on the phase compositions, microstructures and microwave dielectric properties of MgAl_2O_4 ceramics have been investigated. The MgAl_2O_4 could form a solid solution with Mg_2TiO_4, and the grain size of the (l-x)MA-xMT ceramics gradually increased with the increase of sintering temperature. The dielectric constants (ε_r) of (l-x)MA-xMT ceramics steadily increased with the increase of Mg_2TiO_4 content. The ε_r values were mainly affected by secondary phase and dielectric polarizability. The quality factor (Qf) of (l-x)MA-xMT ceramics was closely related to the relative density, secondary phase, cation vacancies and Ti valence; whereas the temperature coefficient of resonance frequency (τ_f) highly depended on the Al-site bond strength. For the sample at x = 0.9, the 0.1MA-0.9MT ceramics sintered at 1350 °C for 4 h exhibited the optimized microwave dielectric properties: ε_r = 12.36, Qf = 236,600 GHz and τ_f = -61 ppm/°C.
NSTL
Elsevier