High dense structure boosts stability of antiferroelectric phase of NaNbO3 polycrystalline ceramics

For NaNbO3, its intrinsic phase transition sequence is still controversial in literature. In this paper, high-densified NaNbO3 ceramics derived from mechanochemical nanostructures presented a stabilized antiferroelectric characteristic. In addition to the Tc of 360 °C, another diffuse dielectric anomaly appeared around 100 °C, which did not vanish after O2 annealing treatment. The fine structure analysis indicated that this dielectric anomaly belongs to first order phase transition from P phase to Q phase. Moreover, even exerting the strong electric field close to breakdown value, the normal ferroelectric loops cannot be induced, proving the large free energy difference between these two phases.