Effect of rare-earth doping on the dielectric property and polarization behavior of antiferroelectric sodium niobate-based ceramics

The lead-free 0.96NaNbO3-0.04CaSnO3 ceramics with rare-earth dopants (La, Sm and Lu) (NCLn100x) were prepared and characterized. It is found that a certain amount of La substitution stabilizes the antiferroelectric (AFE) phase but alleviates the lattice distortion in the fresh samples. Re-entrant-like characteristics are observed in the temperature – dielectric constant curves with the room temperature P phase gradually replaced by a possible R phase. Relaxor-like hysteresis loops with suppressed hysteresis loss and remanent polarization were obtained at high La content, achieving a relatively high Wre of 2.1 J/cm3 at a low electric field (250 kV/cm). The relaxation behaviors of the ferroelectric (FE) domain measured by piezoresponse force microscopy suggest an even long characteristic relaxation time of field-induced FE phase, which is different from the situations of other AFE perovskites. Via an explanatory defected diatomic chain model, we propose that a much larger mass of substitutive ion than the origin one helps to induce low-frequency localized mode, which is believed to be in favor of the formation of polar nano-regions and hence strengthens the dynamic stability of FE phase during electric field loading. Our research provides a further understanding of the tuning strategy for enhancing the antiferroelectricity of the NaNbO3-based system.