Sintering behavior, lattice vibrational characteristics and dielectric properties of B-site ion substituted BaWO4 ceramics for LTCC applications

The influences of Mo 6+ substitution at the B-site of scheelite structure on the sintering character, microstructures, lattice vibrational characteristics, and dielectric properties of BaW 1- x Mo x O 4 ( x = 0.10–0.30) ceramics were studied in detail in this paper. The sintering temperature of BaW 1- x Mo x O 4 ceramics was effectively reduced to less than 950 °C through forming a scheelite solid solution. The densification and the quality factor ( Q × f ) of BaW 1- x Mo x O 4 ceramics were also enhanced compared with pure BaWO 4 ceramic. Raman spectroscopy confirmed that the dielectric constant (ε r ) was highly correlated with molecular polarizability, and the Q × f was strongly dependent on the symmetric stretching bond of [WO 4 ] tetrahedron. Oxygen bond valence was one of crucial parameters for modulating the temperature coefficient of resonant frequency (τ f ). Interestingly, the BaW 0.75 Mo 0.25 O 4 ceramic sintered at 910 °C exhibited favorable microwave dielectric properties of ε r = 9.44, Q × f = 46,820 GHz (@12.5 GHz), and τ f = −69.2 ppm/°C. Meanwhile, the BaW 0.75 Mo 0.25 O 4 ceramic had stupendous dielectric properties in low-frequency band: ε r = 17.5 and dielectric loss (tan δ ) = 2.2×10 −4 (@10 MHz). In addition, there was good chemical compatibility between BaW 0.75 Mo 0.25 O 4 ceramic and silver electrodes. These findings evidence that BaW 1- x Mo x O 4 ceramics are competitive candidates in LTCC technology.