A low-loss, low temperature sintering dielectric using Ba1- x Sr x Mg2(VO4)2 ceramics and its applications at microwave frequencies

Highlights: • The microwave dielectric properties of polycrystalline Ba_1-xSr_xMg₂(VO₄)₂ were investigated. • The variance of ${\epsilon }_r$ and Q×f of the ceramics was small at a minor x value; however, the τ_f value was found to vary from –41.7 ppm/°C at x = 0 to –4.5 ppm/°C at x = 0.15. • For LTCC applications, the stoichiometry Ba_0.85Sr_0.15Mg₂(VO₄)₂ compound is suggested as it possess a high Q×f of 71,000 GHz associated with a ${\epsilon }_r$ of ~ 13.1 and a ${\tau }_f$ of ~ –4.5ppm/°C. • Moreover, the implemented U-type band-pass filter using Ba_0.85Sr_0.15Mg₂(VO₄)₂ substrate also possessed excellent performances. Polycrystalline Ba_1-xSr_xMg₂(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 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_0.85Sr_0.15Mg₂(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.