Low-fire processing of microwave (Ca1−xSrx)(Zr1−yMny)O3 dielectric with Li2O-B2O3-SiO2 glass in H2/N2

The effects of Li2O-B2O3-SiO2 (LBS) glass addition on densification and dielectric properties of (Ca1−xSrx)(Zr1−yMny)O3 fired in a reducing atmosphere have been investigated. The dielectric properties of (Ca1−xSrx)ZrO3 become better with decreasing the ratio of Sr/Ca. Substituting Zr by 0.2 mol Mn, the dielectric loss of (Ca0.9Sr0.1)ZrO3 is greatly reduced, resulting in a Q × fr value of 30500 GHz. To reduce the densification temperatures of (Ca0.9Sr0.1)(Zr0.8Mn0.2)O3 (CSZM9182) to the range cofirable with Cu electrode, 5-10 vol% LBS glass is added and the densification temperature is lowered from 1500 °C to 1030 °C. The densification is further enhanced with increasing [B2O3]/[SiO2] ratio in the LBS glass, however, the dielectric properties are deteriorated. The above result is attributed to a chemical reaction taking place at the interface of CSZM9182-LBS during firing, which becomes more extensive with increasing [B2O3]/[SiO2] ratio in the LBS glass and tends to form a second phase of CaZr4O9. For the LBS glass with 40 mol% Li2O, 20-50 mol% B2O3, and 10-40 mol% SiO2, the resulting CSZM9182 +5-10 vol% LBS microwave ceramics have a dielectric constant of 23-27, Q × fr value of 2500-22,000 GHz at 7.6-7.8 GHz, and a temperature coefficient of resonant frequency (τf) of −22~ −7 ppm/°C in the temperature range between 25 °C and 80 °C.