Ultra‐low fired fluoride composite microwave dielectric ceramics and their application for BaCuSi2O6‐based LTCC

A total of 14 fluoride composite ceramics were prepared through solid‐state method and their microwave dielectric properties were investigated. Among the fluoride composite ceramics, 0.36LiF–0.39MgF2–0.25SrF2 (LMS) had the lowest sintering temperature (600°C) and presented a dielectric constant (εr) of 6.24 ± 0.05, a quality factor (Q × f) of 33 274 ± 900 GHz, and a temperature coefficient resonant frequency (τf) of −86.74 ± 8 ppm/°C. As the LMS ceramic had a low melting point (646°C), it can be used as sintering aid for LTCC applications. The sintering temperature of BaCuSi2O6 decreased from 1050°C to 875°C with 2 wt% LMS doped and excellent microwave dielectric properties of εr = 8.16 ± 0.04, Q × f = 24 351 ± 300 GHz, and τf = −9.74 ± 1 ppm/°C were obtained. Moreover, BaCuSi2O6‐2 wt% LMS can be co‐fired with Ag powders, which makes it a potential new candidate for LTCC applications.