Effects of Gold Nanoparticle Addition on Microstructure and Electrical Properties of PZN-Based Ferroelectric Ceramics

Abstract

In order to investigate the processing-structure-property relationships that exist among conditions of fabrication processing, phase formation, microstructure and electric properties of lead zinc niobate, (PZN)-based systems, in this study, such relationships are brought out via three main parts and discussed in terms of their phase formation, densification, microstructural and dielectric properties. The first part aims to understand the influence of novel Zn3Nb2O8 B-site precursor on the fabrication of PZN ceramics. A combination of Zn3Nb2O8 B-site precursor and reactive sintering techniques has been employed for the fabrication of PZN ceramics. However, the obtained results show that it is difficult to fabricate pure perovskite PZN ceramics. Only pyrochlore-type Pb1.83Zn0.3Nb1.25O5.305 phase was found in all samples and its local structure was investigated using the X-ray absorption spectroscopy technique. The obtained results indicate that the bond length between Zn2+ and Pb2+ in the pyrochlore phase, where Nb5+ sites have been substituted by Zn2+, was found to be longer than the bond length in the perovskite phase. The second part aims to understand the effect of high perovskite phase stabilizer BaTiO3 (BT) additive on the fabrication of PZN-based ceramics. It is seen that dense, pure perovskite ceramics with homogenous microstructure and better dielectric properties can be obtained via Zn3Nb2O8 B-site precursor technique. 0.07 mol% of BT additive content was found to be sufficient to suppress the pyrochlore phase formation in the fabrication of PZN-based ceramics. With appropriated sintering at 1150 oC for 5 h, 0.93PZN-0.07BT ceramics with r,max ~ 11,497 and tan ~ 0.05 at TC (~ 99 oC) when measure at 1 kHz are obtained. Moreover, by applying suitable two-stage reactive sintering schemes, it has been found that dense and pure perovskite 0.93PZN-0.07BT ceramics with fine grain size can be successfully achieved with good dielectric properties. The final part aims to investigate the effect of gold nanoparticles (AuNPs) additive on the fabrication of PZN-based ceramics. By using small angle X-ray scattering technique, it can be seen that synthesized AuNPs exhibit spherical particles with an average diameter of ~ 14 nm. It was found that the addition of AuNPs was effective in decreasing the reactive sintering temperature and increasing the density of the PZN-based ceramics. The average grain size was significantly less than those ceramics without AuNPs. Moreover, broader diffuse phase transition, higher dielectric constant and lower dielectric loss are observed in the PZN-based ceramics modified with AuNPs. In addition, it is seen that the temperature coefficient of the capacitance of the PZN-based ceramics added with AuNPs met the Z5V characteristic, which is suitable for multilayer capacitor applications.