Interplay Between Intrinsic and Extrinsic Losses and Mechanical Enhancement Mechanisms in BaSi ₂ O ₅ Ceramics

ABSTRACT

This study systematically investigated the microstructural defect evolution, microwave dielectric properties, and mechanical performance of BaSi ₂ O ₅ ‐ x Li ₂ CO ₃ ‐B ₂ O ₃ ‐CaCO ₃ ‐CuO (LBCC) ceramics. The results demonstrate that with an increase in LBCC content, local lattice distortion is significantly suppressed and the oxygen vacancy concentration monotonically decreases, thereby substantially mitigating anharmonic phonon–phonon scattering. Simultaneously, the liquid‐phase‐assisted sintering effect drives a continuous enhancement in ceramic densification. However, the experimentally measured Q×f values ultimately exhibit a downward trend due to a strong competitive mechanism, profoundly indicating that the extrinsic dielectric loss introduced by the high‐loss LBCC glass phase completely overwhelms the intrinsic benefits derived from defect suppression and enhanced densification. Specifically, the reduction in localized distortion drives τ _f in the negative direction by suppressing anharmonicity, while the increase in density directly contributes to the marked enhancement in mechanical properties. When sintered at 1000°C with an LBCC content of 4 wt%, the ceramics achieve excellent comprehensive performance: ε _r = 7.26, Q×f = 26034 GHz, τ _f = −31.32 ppm/°C, and a flexural strength of 258.7 MPa. This ceramic system combines favorable sintering characteristics, microwave dielectric response, and mechanical reliability, demonstrating broad application prospects in the field of radio‐frequency microwave devices.