Processing strategy and composite regulation on dielectric performance in Li₂O–Al₂O₃–B₂O₃ dielectric systems using SrTiO₃

In this paper, we investigated the effect of processing parameters and composite regulation on the structure and property relationship of lightweight low-permittivity Li₂O–Al₂O₃–B₂O₃ dielectric system. Li₂BAlO₄ ceramic and (1 − x)Li₂BAlO₄–xSrTiO₃ ceramics were synthesized using a conventional solid-state reaction method. Thermodynamic analysis, sintering temperature, phase formation, crystal structure, and microwave dielectric properties were investigated. Thermal analysis revealed a melting temperature of 847°C, suggesting a comparatively low temperature for the sintering of Li₂BAlO₄ ceramics. Li₂BAlO₄ crystalized into a monoclinic structure with P21/c space group, with [Al₂B₂O₈] rings connected by [BO₃] triangles and [AlO₄] tetrahedra through Al–O–Al bridges. Dense Li₂BAlO₄ ceramics with a relative density of ∼97.7% were sintered at 750°C and had optimal microwave dielectric properties with relative permittivity (ε_r) of 5.13, quality factor (Q × f) of 22 610 GHz, and the temperature coefficient of resonance frequency (τ_f) of −112.5 ppm/°C. The 0.88Li₂BAlO₄–0.12SrTiO₃ composite ceramic has excellent microwave dielectric properties with ε_r = 8.83, Q × f = 14 000 GHz, τ_f = 4.6 ppm/°C. The ceramics also demonstrated an inert behavior with silver electrodes proving its application in low-temperature cofired ceramic (LTCC) technology.