Characterization of KNbO3 nanoplates synthesized by a stirred hydrothermal process

• Nanoplates KN morphology was obtained thanks to the stirring during synthesis.
• Each plate thickness contains about 20 cells of orthorhombic KN.
• Concentration of OH− was followed with calcination temperature by FTIR.
• Dielectric proprieties of KN nanoplates show εr=540 and tangδ=0.03.
• We observed a relaxation phenomenon in curves of dielectric losses below 150 K.

Lead free piezoelectric KNbO3 (KN) nanoplates were successfully synthesized through reaction between Nb2O5 and KOH at 220 °C and 10 M KOH during 8 h. The influence of stirring hydrothermal process on the morphology was studied. X-ray patterns confirm the formation of a pure compound with a significant increase in lattice parameters relative to the bibliography. FTIR and TG measurements show the presence of hydroxyl groups located at the surface and in the bulk sample. Transmission electron microscopy observation highlights the formation of superimposed plates of KNbO3. The thickness of the plates corresponds to about twenty cells of orthorhombic KN. The measured dielectric constant εr and tangδ are 540 and 0.03, respectively at 1 kHz and room temperature. A relaxation phenomenon of domains walls has been observed below 150 K in the losses curves and between 450 and 530 K for the permittivity curves.