Effects of A/B-Site Co-Doping on Microstructure and Dielectric Thermal Stability of AgNbO3 Ceramics

Abstract

AgNbO3-based lead-free ceramics are a promising candidate material for capacitors, where thermal stability is a key property for applications in severe and complex environments. This study investigated the fabrication of Ag1-3xBixNb1-3/5x(Zn1/2Ti1/2)xO3 (ABNZT-x) (x = 0, 0.005, 0.01, 0.02, or 0.04) via a solid-state reaction under oxygen flow. The microstructure, dielectric properties, and impedance spectra of the AgNbO3 samples co-doped with Bi3+, Zn2+, and Ti4+ were systematically characterized. All samples exhibited an orthorhombic phase structure, where the average grain size decreased with increasing co-doping level, the grain growth kinetics was studied by phase-field simulation. The phase transition temperatures became lower and the maximum permittivity values decreased. These findings demonstrated that enhanced dielectric thermal stability had been achieved. The grain conduction effect was observed during the impedance spectroscopy analysis, where the calculated activation energy decreased with increasing co-doping level. This ABNZT-x ceramic system exhibited stable dielectric properties, and shows promise for use as a functional material in electronic devices.