Temperature stable (1-x)BaAl₂Si₂O₈-xBa₃V₂O₈ (0.2 ≤ x ≤ 0.5) microwave dielectric composite ceramics for LTCC applications

BaAl₂Si₂O₈ microwave dielectric ceramics possess dielectric properties of low permittivity (ε_r) and low loss, coupled with low synthesis cost, making them promising for commercialization. However, the hexagonal structure undergoes high-temperature phase transitions that deteriorate thermal shock resistance and durability, hindering its practical use. In this work, we report temperature-stable BaAl₂Si₂O₈-Ba₃V₂O₈ low temperature co-fired ceramics (LTCC). The combination of Ba₃V₂O₈ and G9 glass achieved a near-zero τ_f and a thermal expansion coefficient of ∼ 8.5 ppm/℃, significantly enhancing the temperature stability of BaAl₂Si₂O₈ ceramics. By employing ion substitution and enhancing lattice disorder, the components of G9 glass were strategically designed to successfully induce hexagonal-to-monoclinic transformation of BaAl₂Si₂O₈ phase. The dielectric properties of 0.5BaAl₂Si₂O₈-0.5Ba₃V₂O₈-9 wt% G9 sintered at 900 ℃ were ε_r ∼9, Q×f ∼22,000 GHz and τ_f ∼ +1.9 ppm/℃. Good chemical compatibility with silver powders was confirmed by further investigation of the co-firing behavior. This work provides attractive candidate for BaAl₂Si₂O₈-based LTCCs and an available approach for modifying BaAl₂Si₂O₈ ceramics.