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 Li 2 O–Al 2 O 3 –B 2 O 3 dielectric system. Li 2 BAlO 4 ceramic and (1 − x )Li 2 BAlO 4 – x SrTiO 3 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 Li 2 BAlO 4 ceramics. Li 2 BAlO 4 crystalized into a monoclinic structure with P21/c space group, with [Al 2 B 2 O 8 ] rings connected by [BO 3 ] triangles and [AlO 4 ] tetrahedra through Al–O–Al bridges. Dense Li 2 BAlO 4 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 0.88Li 2 BAlO 4 –0.12SrTiO 3 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.