Phase evolution and enhanced dielectric properties of BaO·Nd ₂O ₃·TiO ₂·B ₂O ₃ glass-based dielectrics containing CaCu ₃Ti ₄O ₁₂

CaCu ₃Ti ₄O ₁₂ (CCTO) has been studied as a filler for the potential high k LTCC (low temperature co-fired ceramics) materials based on a nonconventional BaO·Nd ₂O ₃·TiO ₂·B ₂O ₃ glass in terms of firing temperature and CCTO content. The material system was proven to be high crystallizable as the resultant crystalline phases of BaTi(BO ₃) ₂, BaNd ₂Ti ₅O ₁₄ and NdBO ₃ were observed. The relative content of the crystalline phases were strongly dependant on firing temperature and CCTO content. Interestingly, the 30 wt% CCTO sample showed early densification at 610-670 °C and then unexpected expansion after 850 °C. The 40-60 wt% CCTO samples showed the unexpected secondary densification behavior over the temperature range of 850-950 °C. As a promising example, a combination consisting of the glass and 40 wt% CCTO exhibited k ∼55 and tan δ ∼0.07, which is very rare at this low sintering temperature of 850 °C. These materials system were found to be chemically very stable especially in the H ₂SO ₄ acid solution.