5ZnO·2B2O3–Pb1.5Nb2O6.5 microwave dielectric ceramics with near-zero temperature coefficient of resonant frequency

The effects of Pb1.5Nb2O6.5 addition were investigated on the densification, phase evolution, microstructure, and microwave dielectric properties of 5ZnO·2B2O3 ceramics. It was shown that a 5.5 mol% addition of Pb1.5Nb2O6.5 to 5ZnO·2B2O3 ceramics successfully tailored its temperature coefficient of resonant frequency (τf) from −80 to ~0 ppm/°C and lowered its sintering temperature from 955 to 890 °C without degrading its microwave dielectric properties. 5ZnO·2B2O3 ceramics sintered at 890−910 °C for 3 h with 5.0−6.0 mol% Pb1.5Nb2O6.5 additions exhibited excellent microwave dielectric properties: εr=7.8−8.3, Q×f=11,500−15,200 GHz, and −9.2 ppm/°C≤τf≤+6.6 ppm/°C @ ~7.4 GHz. The ceramics showed cofiring compatibility with Ag and were therefore novel candidates for LTCC substrates.