The relationship between dielectric, ferroelectric properties and microstructure of Mn-doped NaNbO3-based ceramics

Moderate Mn doping at x  = 0.01 pins ferroelectric domains, yielding slim hysteresis loops and optimal energy-storage efficiency. • Higher Mn doping of x  ≥ 0.02 induces a phase transition of coexisting AFE P and FE Q phases, in which the FE Q phase can broaden hysteresis loops and increase energy-storage density. • With increasing doping content of Mn, the site of Mn substitution transitions from A site to B site. (1- x )NaNbO 3 - x MnO 2 ceramics were synthesized via solid-state reaction method. X-ray diffraction with Rietveld refinement shows that increasing Mn content induces a phase transition from a single antiferroelectric P phase ( Pbcm ) to the coexistence of P and ferroelectric Q phases ( P2 1 ma ). Scanning electron microscopy indicates that Mn doping promotes grain growth. Dielectric patterns demonstrate that moderate Mn doping with x  = 0.01 effectively suppresses leakage current and reduces dielectric loss (tanδ = 0.526 at 25 °C and 56.4 MHz). Electrical measurements show that the composition of x  = 0.01 achieves the optimal energy-storage efficiency, and the composition of x  = 0.025 attains the recoverable energy-storage density of 0.531 J/cm 3 . The study illustrates that Mn doping tunes phase composition and defects, thereby optimizing the energy-storage properties of lead-free NaNbO 3 -based ceramics.