Low-temperature sintered MgWO4–CaTiO3 ceramics with near-zero temperature coefficient of resonant frequency

The phases, microstructure, composition analysis and microwave dielectric properties of (1 − x)MgWO4–xCaTiO3 ceramics with Li2CO3–4H3BO3 additions prepared by solid-state reaction method have been investigated by using X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy and advantest network analyzer. The τf of (1 − x)MgWO4–xCaTiO3 were dependent on phase constitutions. The microwave dielectric properties of 0.91MgWO4–0.09CaTiO3 ceramics with Li2CO3–4H3BO3 were characterized, the results indicated that the ɛr and Q × f were associated with the sintering temperature and amount of Li2CO3–4H3BO3. The sintering temperature of ceramics was reduced to 950 °C from 1150 °C and τf was modified to 0 ppm/°C with good Q × f. Addition of 5.0 wt% Li2CO3–4H3BO3 in 0.91MgWO4–0.09 CaTiO3 ceramics sintered at 950 °C showed excellent dielectric properties of ɛr = 15.5, Q × f = 20,780 GHz (f = 7.1 GHz) and τf ∼ 0 ppm/°C. The material has a chemical compatibility with silver, making it a very promising candidate materials for LTCC applications.