Study Of Structural, Electrical And Optical Properties Of Lead-Free (Bi0.5na0.5)Tio3 Based Ceramic Systems

Abstract

In view of the processing and environmental issues pertaining to lead-based ferroelectric materials, investigations on lead-free ferroelectrics are carried intensively in recent years. These materials are interesting because they are flexible with respect to structural changes and functional properties. This study focuses on a lead-free, high temperature ceramic capacitor material having the base composition of (Bi0.5Na0.5)TiO3. The goal is to modify this base composition to create a material that has diffuse-phase-like dielectric behaviour, while maintaining its inherently good high temperature dielectric properties. This will alleviate some circuit design problems, and will create a component that is less susceptible to drastic environmental changes. Areas of interest include aerospace and weapons system applications, motor control, geological down-hole-drilling equipment and many more. An extensive experimental compositional matrix, along with theoretical modelling, has been investigated to modify the base material to attain the goals set forth.(Bi0.5Na0.5)TiO3, SrTiO3, BaTiO3 and Ba(Zr0.25Ti0.75)O3 ceramics were successfully calcined by two stapes conventional solid-state reaction method. The solid-solutions of (1-x)(Bi0.5Na0.5)TiO3-xSrTiO3, (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 and (1-x)(Bi0.5Na0.5)TiO3-xBa(Zr0.25Ti0.75)O3 with concentrations 0 ≤ x ≤ 0.08 were prepared successfully by conventional solid-state reaction route. The optimized sintering temperature is found to be 11500C for 4 hrs. The X-ray diffraction study shows that all the compositions are having a single phase perovskite structure which confirms that a complete solid-solution is formed. The lattice parameter and cell volume decreases with increase in solid solution. A morphotropic phase boundary (MPB) exists in (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 at x = 0.07 and in (1-x)(Bi0.5Na0.5)TiO3-xBa(Zr0.25Ti0.75)O3 at x = 0.05. The same thing is also observed in Raman spectroscopy. The microstructure of all samples shows a change of shape from rectangular to quasi-spherical with decrease in grain size. High dense and smaller grain size has affected the conductivity and electromechanical property to achieve a higher value of d33 and kp as well as enhanced the ferroelectric behavior in MPB compositions.