Characterizations of Lead Free BNT-BT-KNN Ceramics Synthesized by Microwave Technique

Abstract

Ferroelectrics have experienced a great deal of interest for more than half a century. Initially, ferroelectric ceramics were used as capacitor materials due to their high dielectric constants. With the preface of lead-zirconate-titanate (PZT), applications spread to transducers, actuators and many others. But because of the toxic nature of lead and serious environmental concerns there is an urgent need to develop lead free ferroelectrics to replace the currently leading lead based PZT. However, recognized lead-free ferroelectrics are not yet good enough to replace lead based materials. A considerable research attempt into lead-free alternatives to PZT began a few years ago. The purpose of this project was to develop leadfree ferroelectrics, which may ultimately replace PZT. The concept of combining three ferroelectric materials, which is before now morphotropic phase boundary compositions, in order to additional increase the ferroelectric properties was studied in detail. The three base compositions chosen were (0.89BNT-0.06BT-0.05KNN) and (0.92BNT-0.06BT-0.02KNN). BNT-BT-KNN was prepared by the solid state route. Calcination of the samples was done by using microwave at 900oC for both 10 and 20 minutes. In both the cases the phase was formed and the 10 minutes calcined samples were chosen for further synthesis to reduce the processing time. XRD of the compositions was done in which a single perovskite phase was formed. The samples were sintered using the microwave sintering method at 1150oC for 30 minutes. FESEM images of the samples were taken which show dense microstructure with uniform grain size and less apparent porosity. The study of dielectric properties and PE loop measurements were done to prove the ferroelectric nature of the sample.