Low loss Ba3Ti4Nb4O21 microwave dielectric ceramics through (Mn1/3Nb2/3)4+ ion control engineering for LTCC applications

In this work, a new low loss Ba 3 Ti 4- x (Mn 1/3 Nb 2/3 ) x Nb 4 O 21 (MN-BTN, 0 ≤  x  ≤ 12 mol%) ceramics configuration was presented through preparing by the solid-state route. The XRD patterns, Rietveld refinement , microstructure, and microwave properties were systematically analyzed. All the fabricated MN-BTN ceramics belonged to the hexagonal structure with a P 6 3 / mcm space group. More specifically, the 6MN-BTN ceramic exhibited a high relative density of ~92.3 %, homogeneous grains distribution with an average size of ~71.95 µm, and several excellent microwave dielectric properties : ε r = 59.67, Q× f = 16,226 GHz, τ f = +103.9 ppm/℃ sintered at 1220 ℃. The incorporation of 1.5  wt % BaCu(B 2 O 5 ) (BCB) compound within the 6MN-BTN ceramic not only effectively reduced the sintering temperature from 1220 ℃ to 950 ℃, but also the excellent microwave dielectric properties were maintained: ε r = 42.33, Q× f = 11,300 GHz, τ f = +24.7 ppm/℃. Interestingly, the 6MN-BTN + 1.5  wt % BCB ceramic showed better chemical compatibility with Ag. The proposed 6MN-BTN + 1.5  wt % BCB ceramic configuration could be regarded as a promising material for LTCC applications.