Sintering behaviors, microstructures, and dielectric properties of CaO–Al₂O₃–B₂O₃–SiO₂/Ba(Mg_1/3Nb_2/3)O₃ composites for LTCC applications

Herein, (1 − x)CaO–Al₂O₃–B₂O₃–SiO₂ (CABS)/xBa(Mg_1/3Nb_2/3)O₃ (BMN; x = 0.4, 0.45, 0.5, 0.55, and 0.6) composites were prepared, and the impact of the BMN and low-softening-point glass content in CABS/BMN composites on the sintering, dielectric, thermal, and mechanical properties of the prepared composites was investigated. The main crystal phases of the CABS/BMN composites are BMN and Ba₂NaNb₅O₁₅ (BNN). The crystallization temperature of the composite was reduced by an appropriate amount of BMN. BMN ceramics (40–60 wt%) was added to the CABS glass, and the composites were sintered at 800 °C, 825 °C, 850 °C, 875 °C, and 900 °C. To elucidate the influence mechanism of different glass contents and sintering temperatures on the properties of the composites, different qualitative and quantitative instruments were used to study the composite properties. The CABS/BMN composite containing 50 wt% CABS glass sintered at 875 °C exhibits the following ideal properties: volumetric density of 3.57 g/cm³, dielectric constant of 17.97, dielectric loss of 6 × 10⁻⁴, \(Q \times f\) $Q\times f$ value of 10,947 at 9.5 GHz, bending strength of 157.7 MPa, and coefficient of thermal expansion of 5.9 ppm/K. Microstructure analysis reveals that the microstructure of the composite is dense, the pores are few, the surface morphology is uniform and flat, and the composite does not react with silver electrodes, making it suitable for applications utilizing medium dielectric constant low-temperature co-fired ceramic materials at low sintering temperatures.