Co-optimization of microwave dielectric properties in Ba(Mg1/3Ta2/3)O3 complex perovskite ceramics through ordered domain engineering

It is an important subject to improve the temperature coefficient of resonant frequency (τ_f) and thermal conductivity (κ) of microwave dielectric ceramics without reducing the Qf value. Ordered domain engineering was applied to realize the previous objectives in Ba(Mg_1/3Ta_2/3)O₃ ceramics. With the increasing ordering degree from 0.835 to 0.897, the optimized Qf value was obtained. Meanwhile, near zero τ_f from 11.9 to 5.6 ppm °C⁻¹ was achieved, together with increased κ from 5.5 to 7.6 W m⁻¹ K⁻¹, and enhanced dielectric strength from 801 to 921 kV cm⁻¹. The noticeable ordered domain structure with large ordered domains (∼100 nm) and low-energy domain boundaries was revealed in Ba(Mg_1/3Ta_2/3)O₃. The consequent weakened phonon scattering rises the thermal conductivity. The increased bond covalency and oxygen distortion in ceramics with higher ordering degree were suggested as a cause of enlarged bandgap, which enhanced the dielectric strength. The reduced τ_f is dominated by the less “rattling” space of the cations in the ordered state by inducing more positive τ_ε. The reduced τ_f, optimized thermal conductivity, and Qf value in the present work indicate that the ordered domain engineering could open up a new direction for the optimization of microwave dielectric ceramics.