Microwave dielectric properties of Li2W2O7 ceramics improved by Al2O3 addition

Highlights: • 3Li₂W₂O₇–Al₂O₃ ceramics promising candidate as LTCC dielectrics for LTCC applications. • Only two phases Li₂W₂O₇ and Al₂O₃ were observed in all specimens. • 3Li₂W₂O₇–Al₂O₃ ceramics sintered at 700 °C for 2 h possessed an optimal microwave dielectric properties. • The ε_r of 8.2, Q × f value ∼20552 GHz, and zero τ_f = −112 ppm/°C were obtained for 3Li₂W₂O₇–Al₂O₃ ceramics. The effect of Al₂O₃ addition on the densification, sintered behavior, phase composition and microwave dielectric properties of Li₂W₂O₇ ceramics prepared by conventional solid-state reaction method had been investigated. The structure, phase composition and surface morphology were studied by X-ray diffraction, EDX and scanning electron microscopy techniques, respectively. Only two phases Li₂W₂O₇ and Al₂O₃ were observed in all specimens. The sintering time of Li₂W₂O₇ ceramics with Al₂O₃ addition could be effectively reduced from 4 h to 2 h. The results showed that the doping of Al₂O₃ could promote the growth of uniform grain and improve effectively the quality factor and temperature coefficient of resonant frequency (τ_f). The 3Li₂W₂O₇–Al₂O₃ ceramics sintered 700 °C for 2 h exhibited ε_r of 8.2, Q × f of 20,550 GHz, and τ_f of −112 ppm/°C. The good microwave dielectric properties and relatively low sintering temperature would make 3Li₂W₂O₇–Al₂O₃ ceramics promising candidate as LTCC dielectrics for LTCC applications.