Enhancing giant dielectric properties of Ta5+‐doped Na1/2Y1/2Cu3Ti4O12 ceramics by engineering grain and grain boundary

Abstract

AbstractVarious strategies to improve the dielectric properties of ACu3Ti4O12 (A = Sr, Ca, Ba, Cd, and Na1/2Bi1/2) ceramics have widely been investigated. However, the reduction in the loss tangent (tanδ) is usually accompanied by the decreased dielectric permittivity (ε′), or vice versa. Herein, we report a route to considerably increase ε′ with a simultaneous reduction in tanδ in Ta5+–doped Na1/2Y1/2Cu3Ti4O12 (NYCTO) ceramics. Dense microstructures with segregation of Cu– and Ta–rich phases along the grain boundaries (GBs) and slightly increased mean grain size were observed. The samples prepared via solid‐state reaction displayed an increase in ε′ by more than a factor of 3, whereas tanδ was significantly reduced by an order of magnitude. The GB–conduction activation energy and resistance raised due to the segregation of Cu/Ta–rich phases along the GBs, resulting in a decreased tanδ. Concurrently, the grain–conduction activation energy and grain resistance of the NYCTO ceramics were reduced by Ta5+ doping ions owing to the increased Cu+/Cu2+, Cu3+/Cu2+, and Ti3+/Ti4+ ratios, resulting in enhanced interfacial polarization and ε′. The effects of Ta5+ dopant on the giant dielectric response and electrical properties of the grain and GBs were described based on the Maxwell–Wagner polarization at the insulating GB interface, following the internal barrier layer capacitor model.