A novel CaCu2.8-xZnxTi4O12 system: a high-performance dielectric with nonlinear J − E properties

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 CaCu 2.8- x Zn x Ti 4 O 12 ( x = 0.00 – 0.10) ceramics sintered at 1100 °C for 8 and 12 h. Nonlinear J-E behaviors were observed in these ceramics with an extremely high nonlinear coefficient (α) of ∼10.14 in CaCu 2.75 Zn 0.05 Ti 4 O 12 sintered for 12 h. Additionally, a breakdown electric field ( E b ) was found to increase in samples with a high Zn 2+ 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 TiO 2 and CaTiO 3 minor phases with Zn 2+ ions in the main CaCu 3 Ti 4 O 12 phase. Improved dielectric properties and nonlinear J-E behaviors are discussed based on the increased grain boundary resistance ( R gb ) due to the presence of minor phases and substitution of Zn 2+ ions at the Cu 2+ sites of CaCu 2.8- x Zn x Ti 4 O 12 . The XPS results confirmed that electrons could hop at the Cu + − O − Cu 2+ and Cu 3+ − O − Cu 2+ sites, indicating the presence of semiconducting grains in these ceramics.