Emerging antiferroelectric phases with fascinating dielectric, polarization and strain response in NaNbO3-(Bi0.5Na0.5)TiO3 lead-free binary system

Abstract Environmentally-benign antiferroelectrics (AFEs) have attracted a great deal of attention in recent years owing to their special structure and polarization/strain-electric field response, exhibiting giant application advantages in multifunctional devices. In this work, a detailed phase diagram in a binary lead-free system between AFE NaNbO3 (NN) and ferroelectric (FE) (Bi0.5Na0.5)TiO3 (BNT) was established according to the measurement of dielectric and ferroelectric properties in combination with the multiscale structure analysis such as Raman spectra, synchrotron x-ray diffraction and transmission electron microscopy. Multiple AFE phases of different stability, crystal symmetry and domain morphology were stabilized near room temperature, involving AFE orthorhombic P (Pbma) and R (Pnma) phases in NN-rich compositions and AFE tetragonal phase (P4bm) in BNT-rich compositions, as well as field induced metastable AFE monoclinic phase (P21). Owing to the electric field induced AFE-FE phase transformation especially for relaxor AFEs with antipolar nanoregions, tunable and excellent electrical properties of temperature-stable dielectric permittivity, ultrahigh energy-storage density and efficiency and low-hysteresis high strain can be generated in the proximity of these AFEs, showing outstanding potentials in thermally-stable capacitors, dielectric energy storage and large-strain ceramic actuators for NN-BNT solid solutions.