High dielectric constant (k) CaCu3Ti4O12 (CCTO) has been studied as a potential filler for low‐temperature cofired ceramics (LTCC) based on typical calcium aluminoborosilicate glass. CCTO does not appear to be chemically reactive with the glass regardless of the firing temperature over the compositional range of 30–90 wt% CCTO. Dielectric constant and dielectric loss turned out to depend strongly on the relative content of CCTO and firing temperature. As an optimal composition, the glass with 60 wt% CCTO exhibited a k∼32 and tan δ∼0.01 as a result of firing at 850°C, which is preferably applicable for the medium k LTCC applications. The higher content of 90 wt% CCTO needed to be densified at 900°C for better densification with a higher dielectric constant of ∼150. However, the 900°C firing was not acceptable for the 30 and 60 wt% CCTO‐containing samples due to the unexpected expansion of samples leading to significantly enlarged pores.
Uncommon low loss Mg 1?5 Zn 0?5 SiO 4 ceramics containing Bi 2 O 3 were investigated by focusing on the roles of Bi 2 O 3 on phase evolution and resultant microwave dielectric properties. While the primary goal of lowering sintering temperature can be easily assumed, some unexpected behaviours of the Bi 2 O 3 containing materials are highlighted with experimental evidences concerning selective dissolution of Zn 2 SiO 4 and grain boundary segregation of gradual Bi richer phases. These evidences are strongly dependent on the content of Bi 2 O 3 and sintering temperature. As an optimal composition, Mg 1?5 Zn 0?5 SiO 4 with 0?5 mol.-%Bi 2 O 3 exhibited promising dielectric properties of a k value y6?8 and a Q6f value y23 300 at a sintering temperature of 1150uC, which is much lower than typical sintering temperature of 1450uC.
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