Suppression of intermediate antiferroelectric phase in sub-micron grain size Na 0.5 Bi 0.5 TiO 3 ceramics

Lead-free NBT ceramics with average grain sizes ranging from sub-micron (0.38 µm), micron (1.23 µm) and large-micron (3.65 µm) were prepared and the influence of grain size on structural, dielectric and ferroelectric properties are discussed in the present work. The effect of grain size on the intrinsic properties such as octahedral tilting, bond length, bond angle, octahedral distortion, crystallite size, lattice strain and lattice parameters were measured. Herein, the structural and the morphological properties at different sintering times were in direct congruence with the temperature-dependent dielectric and ferroelectric response of pure NBT ceramics and an intermediate antiferroelectric (AFE) phase suppressed in sub-micron NBT. This unusual feature of sub-micron NBT was thoroughly studied and distinguished from large-grain NBT ceramics. Based on the temperature-dependent P–E loops the maximum adiabatic change in temperature ∆T max = − 0.81 K was obtained at the field strength of 55 kV/cm in micron NBT. Further, the large energy storage density of about W rec = 0.55 J/cm 3 was achieved by AFE phase transition in micron NBT through P–E loop data. Because of the coexistence of electro-caloric effect (ECE) and energy storage properties, the micron NBT was found to be the optimum grain size corresponding to the best dielectric and ferroelectric properties and therefore this porous-free NBT was suitable for application in functional devices.