Phase evolution and grain-boundary contributions in CaCu _3-xZn _xTi ₄O ₁₂

Extensive substitutions of Zn in Ca(Cu _1-xZn _x) ₃Ti ₄O ₁₂ (x = 0, 0. 1, 0. 5, 1. 0 and 2. 0) dielectrics are investigated in terms of the phase evolution, dielectric properties and grain boundary resistivity. The composition of CaCu _{2. 9}Zn _{0. 1}Ti ₄O ₁₂ (x = 0. 1) densified at a relatively low sintering temperature of 1000°C showed a k value of approximately 7,000 and a tanδ value of approximately 0. 07 at 10 kHz, which is better than the values for pure CaCu ₃Ti ₄O ₁₂ (CCTO). The improved dielectric properties are also believed to be related to the lower grain boundary resistivity of ~1676 kΩ. cm, as obtained from a Cole-Cole plot. Beyond this level of Zn, the degradation of the dielectric constant was associated with unexpected crystalline phases, in this case Ca ₂Zn ₄Ti ₁₆O ₃₈, CaTiO ₃, and Zn ₂TiO ₄, which were observed as the level of Zn increased. Although the degradation does not match that of pure CCTO, an addition of Zn up to x=1. 0 can hold the dielectric constant at the level of a few thousands, which is still promising compared to other high-k dielectric materials that must be densified below -1000°C to meet the subsequent microcircuit requirements.