On the coexistence of ferroelectric and antiferroelectric polymorphs in NaNbO3 fibers at room temperature

Na2Nb2O6·H2O fibers were synthesized in a short time using a microwave-assisted hydrothermal method and later used as a precursor for obtaining NaNbO3 fibers with piezoelectric characteristics. The NaNbO3 fibers consist of a mix of antiferroelectric (Pbcm) and ferroelectric (P21ma) orthorhombic phases. The ferroelectric structure comprises about 87% wt of the sample, and a theoretical approach indicated that an electric field could induce an inversion in the relative stability between the most stable antiferroelectric structure and the ferroelectric one. Piezoresponse force microscopy showed that an individual fiber is composed of regions with ferroelectric domains and regions with no ferroelectric characteristics.