A low-loss, low temperature sintering dielectric using Ba1-xSrxMg2(VO4)2 ceramics and its applications at microwave frequencies

Abstract

Polycrystalline Ba1-xSrxMg2(VO4)2 compounds were investigated as a promising microwave dielectric for low-temperature co-fired ceramics (LTCC) applications. The single tetragonal phase was detected for the BaMg2(VO4)2 compound, and a phase transition from BaMg2(VO4)2 to SrMg2(VO4)2 was observed with an increase in the Sr substitution. The Raman spectrum was recorded to clarify the vibration and rotation modes of the specimen. The τf values was improved dramatically from –42.8 to –4.5 ppm/°C with a minute Sr substitution (x = 0.15) in place of Ba. Combined excellent microwave dielectric properties (εr ~ 13.1, Q × f ~ 71,000 GHz and τf ~ –4.5 ppm/°C) can be obtained for specimens using Ba0.85Sr0.15Mg2(VO4)2 sintered at 950 °C for 4 h. In addition, an U-type band-pass filter with two transmission zeroes was designed and fabricated on the ceramic substrates. Not only the circuit size was reduced, an excellent filter performance was also obtained. Thus, these compounds constitute very promising materials for LTCC applications.