Optimization of Zn2GeO4 microwave dielectric ceramics via Cu substitution and B2O3 sintering aid for LTCC application

A series of Zn2-xCuxGeO4 ceramics were prepared by the solid-phase sintering method. Cu2+ substitution for Zn2+ facilitated the single-phase formation and benefited densification via lowering the sintering temperatures, hence thereby the microwave dielectric properties were largely improved. A representative composition with x = 0.08 revealed a homogenous Zn2GeO4 phase with good microwave dielectric properties: εr ∼ 7.47, Q×f ∼ 56,980 GHz, and τf ∼ −13.9 ppm/°C when sintered at 1000 °C. To evaluate the potential application of low-temperature cofired ceramics (LTCC), sintering aids (B2O3) were added to the x = 0.08 sample to reduce its sintering temperature to below 960 °C. A dramatic improvement in Q×f ∼ 107,415 GHz was observed with only 0.5 wt % B2O3 addition. Chemical compatibility was confirmed via cofiring with silver electrodes at 940 °C. All the merits show promising potential for advanced substrates. [Display omitted]