Ultra‐low fired fluoride composite microwave dielectric ceramics and their application for BaCuSi ₂ O ₆ ‐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–0.39MgF 2 –0.25SrF 2 (LMS) had the lowest sintering temperature (600°C) and presented a dielectric constant ( ε r ) of 6.24 ± 0.05, a quality factor ( Q × f ) of 33 274 ± 900 GHz, and a temperature coefficient resonant frequency ( τ f ) 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 BaCuSi 2 O 6 decreased from 1050°C to 875°C with 2 wt% LMS doped and excellent microwave dielectric properties of ε r = 8.16 ± 0.04, Q × f = 24 351 ± 300 GHz, and τ f = −9.74 ± 1 ppm/°C were obtained. Moreover, BaCuSi 2 O 6 ‐2 wt% LMS can be co‐fired with Ag powders, which makes it a potential new candidate for LTCC applications.