Effect of doping on lead-free dielectric ceramics

Abstract

Piezoelectric materials are widely used nowadays in a large number of electronic devices considering their exceptional electrical properties. Lead zirconate titanate (PZT) is the most currently used piezoelectric material; it presents a perovskite structure and has a region, called morphotropic phase boundary (MPB), where an improvement of its properties occurs. However, the major inconvenience with this material is the environmental and health problems arising from the presence of lead as a result of its high toxicity. For this reason the need for researching on lead-free ceramics with similar properties that PZT shows has been recently one of the main objectives of the scientific community. Bi0.5Na0.5TiO3–BaTiO3 (BNT-BT) system is a promising choice for being the substitute of PZT due to the fact that it has perovskite structure as well as a MPB where great piezoelectric response is obtained. Notwithstanding, even with the large number of studies carried out the exact composition where its properties are as remarkable as the PZT ones has not been found. Consequently, it is necessary to continue investigating in this direction. This work is based on the study of how the addition of zirconium as a doping element affects BNT-BT properties. The preparation of BNT-BT based ceramics has been made by solid state reaction with variations on the synthesis conditions and composition of the ceramics. Their characterization has been accomplished with the different techniques used on solid state chemistry. Through XRD the introduction of dopants on the BNT-BT structure has been confirmed and by SEM/EDS ceramics could be found where in the structure the dopant goes. Furthermore, the dielectric likewise the ferroelectric properties could have been studied, obtaining different results depending on the synthesis conditions carried through and the composition