Rapid fabrication of CaTiO3-SmAlO3 microwave ceramics with ultra-high Q × f values and temperature stability for millimeter-wave communication applications

Technologically important titanate-based microwave ceramics usually suffer the deterioration of the dielectric properties from the induced oxygen vacancy during the lengthy sintering process. Rapid densification that could significantly suppress the generation of oxygen vacancies in 0.7CaTiO₃-0.3SmAlO₃ (CT-SA) ceramics is realized by microwave sintering. The oxygen vacancy concentration in CT-SA ceramics sintered by microwave sintering is lower than that of ceramics by conventional sintering, thereby reducing the ion conduction and electrical resistance. CT-SA ceramics sintered by microwave sintering demonstrate better temperature stability, resulting from the attenuated space charge polarization related to oxygen vacancy concentration and the weakened dielectric relaxation processes associated with defect polarization. CT-SA ceramics sintered by microwave sintering for only 1 h exhibit excellent dielectric properties: Q × f=49,300 GHz, ε_r=42.8, and τ_f=0.91 ppm/°C, which is 15% enhancement in Q × f values compared to ceramics by conventional sintering for 4 h. Especially, CT-SA ceramic dielectric resonator antenna fabricated by microwave sintering with >90% radiation efficiency was resonated at 7.85 GHz (S₁₁=−33.98 dB), demonstrating the promising potential for millimeter-wave communication applications.