Structures and properties of LiBaF3 microwave dielectric ceramics for ULTCC applications

Perovskite structural LiBaF 3 ceramics with excellent microwave dielectric properties were synthesized using traditional solid-state method. By regulating the sintering temperatures from 600 °C to 675 °C, LiBaF 3 ceramics exhibit tunable dielectric constant ( ε r ) from 12.42 to 13.72, adjustable Q  ×  f value from 55000 GHz to 73000 GHz, and regulable temperature coefficient of resonance frequency ( τ f ) from −36.78 ppm/°C to −34.68 ppm/°C. The properties are strongly associated with the density, and can be further optimized by 0.5 wt%TiO 2 addition ( ε r  = 14.43, Q  ×  f  = 56000 GHz, τ f  = -1.26 ppm/°C). The LiBaF 3 ceramics also exhibit excellent compatibility with Ag and Al electrodes. Furthermore, relationships between multiscale structures and microwave dielectric properties of the ceramics were revealed. Oxidation behaviors between LiBaF 3 and O 2 would result in the lattice shrinkage, the introduction of defect level, the decrease of bandgap and density, and then deteriorating the microwave dielectric properties. All the findings make the LiBaF 3 ceramic a promising candidate for ULTCC application, and may facilitate the development of other novel microwave dielectric materials.