Factors affecting KNN-modified lead free piezoceramic properties

Abstract

This work reviews currents aspect in (K,Na,Li)(Nb,Ta,Sb)O3 lead free piezoceramics. Nowadays, this material appears as one of the most promising alternatives to the well known PZT piezoelectric ceramics. We highlighted different factors affecting piezoelectric properties. Some practical aspects related composition, processing, structure, microstructure in the study of the lead-free KNL-NTS piezoceramics were analyzed. A comprehensive role of the main secondary phases was attempted. Raman Spectroscopy and X-Ray diffraction, allowed demonstrating a direct correlation between the structural distortion of the tetragonal phase and the ferroelectric and the piezoelectric properties: the higher the tetragonality, the higher the piezoelectric properties. Using these results, we established relationships correlating respectively the ferroelectric properties (Pr), the piezoelectric properties (dij) and the ionic effective displacement (Dzeff) of the active ferroelectric ion with the wavenumber of the A1g mode. Knowing this relationships, Raman spectroscopy can be used to determinate these parameters and be used as a powerful tool to in situ monitor changes of these parameters under different processing conditions.