Determinación de la temperatura de transición de cerámicos piezoeléctricos libres de plomo, mediante impedancia electroquímica

Piezoelectric ceramics with perovskite structure based on lead zirconate titanate (PZT) show excellent electrical properties near the morphotropic phase boundary (MPB) and thus are widely used for actuators, sensors as well as microelectronic devices. However, because of the high toxicity of lead oxide and its high vapour pressure during sintering, the use of lead-based ceramics has caused serious lead pollution and environmental problems; for this reason, the development of lead-free piezoelectric ceramics has been demanded to replace lead-based ceramics. Therefore, it is necessary to develop lead-free piezoelectric ceramics with good properties. Among the lead-free piezoelectric materials, the alkaline niobate-based perovskite compounds and Bi-containing materials, have attracted a large amount of attention because of their superior characteristics. The alkaline niobates (K,Na)NbO₃ (KNN)-based material exhibits especially good piezoelectric properties and have been studied as substitutes for PZT piezoelectrics. In this work, alkaline niobate-based piezoelectric ceramics were sintetized, system (K_0.5Na_0.5)_xLi_(1-x)Nb_yTa_(1-y)O₃, and were characterized by X-ray diffraction (DRX) and scanning electron microscopy (SEM). In order to determine their transition temperature, electrochemical impedance spectroscopy (EIS) was used, and it was found the transition temperature was about 420 °C, which is a desirable value in this kind of materials.