Improved Zn_0.9Mg_0.1Al₂O₄ Microwave Dielectric Ceramics with High Thermal Conductivity

Zn_0.9Mg_0.1Al₂O₄ + x wt.% TiO₂ (0 ≤ x ≤ 3) microwave dielectric ceramics with relatively high thermal conductivity were prepared by solid-phase reaction. The effects of TiO₂ on the crystal phase, micromorphology, microwave dielectric properties, and thermal conductivity of the Zn_0.9Mg_0.1Al₂O₄ ceramics were studied. X-ray diffraction analysis, scanning electron microscopy, laser flash measurements, and network analysis were used in this study. The results showed that a small amount of nonstoichiometric compounds appeared in the Zn_0.9Mg_0.1Al₂O₄ ceramics with increasing TiO₂ content. At the same time, TiO₂ doping promoted growth of crystal grains, opened the ion-exchange channels in the system, promoted the sintering reaction, and reduced the sintering temperature of the Zn_0.9Mg_0.1Al₂O₄ ceramics. Moreover, addition of TiO₂ suppressed the microscopic lattice disorder and macroscopic segregation, leading to an improvement in the dielectric properties and thermal conductivity of the composite ceramics. The Zn_0.9Mg_0.1Al₂O₄ + 2 wt.% TiO₂ ceramic sintered at 1500°C exhibited the best dielectric performance and thermal conductivity with a dielectric constant of 8.57, Q × f product of 18,0861 GHz, temperature coefficient of resonance frequency of −41.5 ppm/°C, and thermal conductivity of 19.67 W/(m K).