A Comprehensive Study on the BaCu2–xSi2O7–x (0 ≤ x ≤ 1) Ceramics with Low Sintering Temperature and Applications in Dielectric Resonant Antenna

Based on the ternary phase diagram of BaO–CuO–SiO2, a series of BaCu2–xSi2O7–x (0 ≤ x ≤ 1) samples were prepared by using the conventional solid-state reaction method. By adjusting the Cu content, the phase composition between BaCu2Si2O7 and BaCuSi2O6 was effectively controlled. These two phases can coexist stably in the sintering temperature range of 1000–1060 °C. This two-phase coexistence state enhances the densification of ceramics. At x = 0.5 and sintered at 1020 °C, the sample exhibited optimal microwave dielectric properties, with a relative dielectric constant (εr) of approximately 8.07. Its Q × f (where Q is the quality factor and f is the resonant frequency) is as high as 47,200 GHz, and the resonant frequency temperature coefficient (τf) is −20.00 ppm/°C. When x = 0.5, adding 1 wt % BaCu(B2O5) (BCB) and 1 wt % LBSCA glass additives significantly reduce the sintering temperature to 890 °C. The samples still exhibit competitive microwave dielectric properties (εr ≈ 7.8, Q × f ≈ 19,900 GHz, τf ≈ −19.00 ppm/°C), along with excellent chemical compatibility with silver electrodes. These findings demonstrate that BaCu2–xSi2O7–x ceramics are promising candidates for low-temperature cofired ceramics technology (LTCC) applications.

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