CONICET | Buscador de Institutos y Recursos Humanos

Lead titanate-zirconates (PZT) are the most studied and commercially used piezoelectric materials. However, they are considered to be pollutant or even hazardous in virtue of the presence of Pb in their composition. A potential substitute based on KxNa1-xNbO3 (KNN), which has shown piezoelectric properties similar to those of PZT, has recently been proposed [1-3]. Nevertheless, the dependence of the electrical response with composition and the difficulties found with its densification, are the main drawbacks to be overcome before the commercial application of KNN [4]. In this work,the hydrothermal method was used for the synthesis of KxNa1-xNbO3 powders aiming to improve the microstructural and dielectric properties of this material. The precursors used were KOH, NaOH and Nb2O5 under different KOH:NaOH ratios. The influence of ionic and non-ionic surfactants on the sinterability and electrical properties of the samples was also studied. The obtained samples were characterized by X-Ray Diffraction (XRD), Raman Spectroscopy (RS) and Electron Scanning Microscopy (SEM). Powders were pressed into discs and heat-treated at 1125ºC. Sintered samples were characterized by means of density measurements, XRD, X-Ray Fluorescence (XRF), SEM and RS. The electrical properties were assessed by Impedance Spctroscopy and hysteresis polarization loops under a strong variable electric field. It was determined that the concentration of K in the lattice increased with the KOH:NaOH ratio and improved the dielectric permittivity values. In addition, the use of surfactants decreased the particle size and improved the apparent density of sintered samples. The hydrothermal method proved to be a satisfactory alternative for the synthesis of KNN powders for the preparation of dense samples with good electrical properties.