**3.2. Obtaining NaNbO3 1D nanostructures modified by polyaniline (PAni)**

PAni (polyaniline) is a conducting polymer in which the electrical conductivity can be modified by the protonation process controlling the reaction pH [15], and its use to cover ceramic particles has the ability to improve the conductivity of particles.

To obtain PAni, the monomer aniline (C6H5NH2) (Sigma-Aldrich) was used after vacuum distillation to remove photoxidized molecules. The oxidant ammonium persulfate was employed for the polymerization process of aniline (MERCK).

To obtain NaNbO3 fiber particles coated with PAni, the fibers were incorporated into a solution of aniline, cloridric acid water solution, 1 mol.L–1, and ammonium persulfate under stirring at temperature around 2°C for approximately 1 hour. This suspension displayed a green color, a feature of protonated PAni (conductive). The deprotonation process was performed by washing the green particles with ammonium hydroxide water solution, 0.1 mol.L–1; in this condition the particles presented a blue color (not conductive). Finally, the particles were protonated again through the use of a solution with pH = 3.7 containing cloridric acid (1 mol.L–1) and ammonium hydroxide (0.1 mol.L–1). At the end of the process, the particles displayed a green color again (conductivity controlled).

Observing the FE–SEM image depicted in Figure 6, it is possible to note that the covering did not change the morphology of the particles.

**Figure 6.** FE–SEM image of (A) NaNbO3 fiber-like particles covered with reprotonated PAni and (B) larger image.
