Good electrical performances and impedance analysis of (1 − x )KNN– x BMM lead-free ceramics

(1 − x)(K0.5Na0.5)NbO3–xBi(Mg0.75Mo0.25)O3 [(1 − x)KNN–xBMM] (x = 0.005, 0.01, 0.02) ceramics were prepared via a solid-state reaction method. X-ray diffraction patterns (XRD) and Raman spectrum showed that a solid solution was formed between the BMM and KNN, which improved the electrical properties of KNN. With increasing the BMM content, the grain firstly increased and then decreased. When x = 0.01, the ceramics exhibited the optimized microstructure, indicating that there exits an optimal doping component. Temperature dependence of relative permittivity also increases firstly and then decreases. The relative permittivity (er) of ~ 1418 in stabilization zone, emax ~ 4861 at the Curie temperature T C ~ 394 °C, good temperature stability ∆e/e123 °C ≤ ± 15% from 123 °C to 348 °C, and the dielectric loss tanδ ≤ 0.036 from 109 to 348 °C were obtained for 0.99KNN-0.01BMM ceramics. Conductivity behavior of the (1 − x)KNN–xBMM was investigated as a function of temperature from 420 to 520 °C and frequency from 40 to 106 Hz, showing that the basic mechanisms of conduction and relaxation processes were thermally activated, and oxygen vacancies were the possible ionic charge transport carriers at higher temperatures.