부산대학교 도서관

Colossal dielectric constants (ε′∼11,550 – 15,535) with very low dielectric loss (tanδ ∼0.013 – 0.033) at 30 °C and 1 kHz were achieved in CaCu2.8-xZnxTi4O12(x = 0.00 – 0.10) ceramics sintered at 1100 °C for 8 and 12 h. Nonlinear J-Ebehaviors were observed in these ceramics with an extremely high nonlinear coefficient (α) of ∼10.14 in CaCu2.75Zn0.05Ti4O12sintered for 12 h. Additionally, a breakdown electric field (Eb) was found to increase in samples with a high Zn2+ion content. To reveal these excellent properties, the phase and microstructure of these materials were explored using XRD and FE-SEM. Elemental mapping and EDXS spectra confirmed the presence of TiO2and CaTiO3minor phases with Zn2+ions in the main CaCu3Ti4O12phase. Improved dielectric properties and nonlinear J-Ebehaviors are discussed based on the increased grain boundary resistance (Rgb) due to the presence of minor phases and substitution of Zn2+ions at the Cu2+sites of CaCu2.8-xZnxTi4O12. The XPS results confirmed that electrons could hop at the Cu+− O − Cu2+and Cu3+− O − Cu2+sites, indicating the presence of semiconducting grains in these ceramics.