Enhancing giant dielectric properties of Ta <sup>5+</sup> ‐doped Na <sub>1/2</sub> Y <sub>1/2</sub> Cu <sub>3</sub> Ti <sub>4</sub> O <sub>12</sub> ceramics by engineering grain and grain boundary
Pariwat Saengvong, Narong Chanlek, Pornjuk Srepusharawoot, Viyada Harnchana, Prasit Thongbai
Abstract
Abstract Various strategies to improve the dielectric properties of ACu 3 Ti 4 O 12 (A = Sr, Ca, Ba, Cd, and Na 1/2 Bi 1/2 ) 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 Ta 5+ –doped Na 1/2 Y 1/2 Cu 3 Ti 4 O 12 (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 Ta 5+ doping ions owing to the increased Cu + /Cu 2+ , Cu 3+ /Cu 2+ , and Ti 3+ /Ti 4+ ratios, resulting in enhanced interfacial polarization and ε′. The effects of Ta 5+ 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.