Preparação e caracterização de cerâmicas piezoelétricas do tipo PZT co-dopadas com nióbio e ferro

Abstract

The piezoelectric ceramics studied in this work, Pb1.03Zr0.53Ti0.47O3, Pb1.03Zr0.525Nb0.05Ti0.465Fe0.005O3, Pb1.03Zr0.515Nb0.015Ti0.465Fe0.005O3, Pb1.03Zr0.525Nb0.005Ti0.455Fe0.015O3 and Pb1.03Zr0.515Nb0.015Ti0.455Fe0.015O3, were all of them sintered between 1200oC and 1250oC for 3.5h. After that, their piezoelectric properties were investigated. In the present work, oxides were used as raw material in both, matrices and dopants. The mixture of the precursor oxides were calcinaned at 850oC during 3.5h for obtaining the PZT phase. The precursor oxides, the powders and the PZT samples went through characterization tests in order to have their microstructures, densities and physical properties correctly determined. After the powders had been conformed and performed the sinterization process, the PZT ceramics were polarized and their piezoelectric properties determined by using an impedancemeter working in the frequency from 100 KHz to 200 KHz. The obtained results from laser dispersion had revealed agglomeration of lead and zirconium oxide. The calcined samples presented particle sizes from 0.44 μm to 0.63 μm. The density analyses using the Archimedes method indicated a good densification of the sintered samples and a weak influence of the sintering temperature on the obtained density values, whose values ranged from 95.73 to 97.65 % of the theoretical density value. Analysis performed using the scanning electron microscopy technique (MEV) revealed that the sintered samples had showed a correlation between the type and concentration of the dopant with their fracture mode, which were transgranular when Fe prevails over the Nb as dopant, and intergranular, when is the Nb that prevails over the Fe as dopant. By the other side, from increasing the sintering temperature resulted transgranular fractures, independently of which type and content of dopant had been used, except for the equimolar case with relatively low content of dopant, whose results were not consistent with the literature related to this material. About the piezoelectric properties, the results had showed that the combination of the dopant composition with the sintering temperature had brought better values of dielectric constant for the equimolar formulation with more content of dopant. Relating to the mechanical quality factor, from the combination of the dopant composition with the sintering temperature had decreased the factor when Fe prevails over Nb and increased the frequency factor when is the Nb that prevails over the Fe.