A low-loss, low temperature sintering dielectric using Ba_(1-x)Sr_xMg_2(VO_4)_2 ceramics and its applications at microwave frequencies

摘要

Polycrystalline Bai_(1-x)Sr_xMg_2(VO_4)_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 BaMg_2(VO_4)_2 compound, and a phase transition from BaMg_2(VO_4)_2 to SrMg_2(VO_4)_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 τ_f 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 (ε_r ～ 13.1, Q ×f～71,000 GHz and τ_f～-4.5 ppm/°C) can be obtained for specimens using Ba_(0.85)Sr_(0.15)Mg_2(VO_4)_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.