Microwave dielectric properties of CaTiO3-AgNbO3 ceramics with ultrahigh dielectric constant

In RF devices, the microwave ceramics possessing an ultrahigh dielectric constant are instrumental in facilitating the miniaturization of electronic components. However, ceramic systems with ultrahigh dielectric constant are rare and typically exhibit poor temperature stability and high dielectric loss. Research on developing new systems with ultrahigh ε r , low dielectric loss, and low τ f is crucial. The microwave ceramics of (1- x ) CaTiO 3 - x AgNbO 3 [(1- x ) CT- x AN, x  = 0.4–0.8] were synthesized via solid-state reaction. The XRD and Rietveld analysis data have confirmed that the CT-AN ceramic system is in an orthorhombic structure with a space group of Pbcm . Elevated AgNbO 3 content leads to increased grain size in ceramics. These ceramics possess a high relative density (>98 %) and show excellent microwave dielectric properties. With increasing AgNbO 3 content, the ε r ascends from 106 to 886, while Q×f descends from 1500 GHz to 381 GHz. And τ f fluctuates within a range of 400–1000 ppm/°C, with a minimum of 403 ppm/°C when x  = 0.5. Dielectric anomalies due to phase transitions were observed within low-frequency spanning 500 Hz to 200  k Hz, and the dielectric loss is zero at 200  k Hz at 25–100 °C. CT-AN ceramics demonstrate an ultrahigh dielectric constant, and further research into modulating its temperature coefficient of the resonant frequency could unlock their potential for applications in miniaturized antennas and capacitors.