Novel low-ε_r and lightweight LiBO₂ microwave dielectric ceramics with good chemical compatibility with silver

High-speed signal propagation systems require dielectric ceramics with low relative permittivity (ε_r) and a high-quality factor (Qxf). In this paper, a novel low-permittivity borate ceramic (LiBO₂) was synthesized using a conventional solid-state reaction method. Based on the X-ray diffraction and Rietveld refinement, the LiBO₂ crystallized into a monoclinic structure with a space group of P21/c. Dense and single-phase ceramic was obtained at 640 °C with comprehensive microwave dielectric properties: a low relative permittivity (ε_r) of 5.3, a moderate quality factor (Q×f) of 18,200 GHz at 16.3 GHz, and a temperature coefficient of resonant frequency (τ_f) of − 66.2 ppm/°C. Good chemical compatibility with Ag electrode and thermal expansion coefficient of 25.4 ppm/°C was achieved demonstrating the potential applications as dielectric resonances in wireless communications and substrates in low-temperature cofired ceramics.