Microstructure and electrical properties of Nb‐doped SrTiO3‐BiFeO3 based lead‐free ceramics

In this work, Nb‐doped 0.75SrTiO3‐0.25BiFeO3 (ST‐BF) lead‐free ceramics are designed and synthesized using a conventional solid‐state reaction method. The influence of Nb doping on the microstructure, dielectric, and electrical properties are systematically investigated. With the increase of Nb concentration, the crystal structure of ST‐BF remains pseudo‐cubic as exhibited in the X‐ray diffraction patterns. The grain size is found to increase from 0.33 to 6.23 μm, and then decrease to 1.88 μm by Nb doping, along with a clear heterogeneous core–shell microstructure. A relatively low dielectric loss (∼0.1, at 1 kHz) and a stable dielectric constant (∼700, at 1 kHz) are obtained for the 0.03 Nb‐doped ST‐BF composition at room temperature. Impedance spectroscopy analysis shows that Nb doping in ST‐BF increases the total resistivity, forming an electrically conductive core and a nonconductive shell, with enhanced activation energy. The results may provide a feasible approach to develop novel ST‐based lead‐free dielectric ceramics for capacitor applications.