Texturing of Lead-free Ferroelectric Ceramics

Abstract

The lead-free ferroelectric system 0.75Bi0.5K0.5TiO3-0.25BiFeO3 has been investigated with respect to crystallographic texturing. Recent studies have shown that the system have promising electromechanical properties and may be an alternative for replacing lead zirconate titanate (PZT). Texturing was performed on the system with the aim of enhancing the electromechanical properties. Phase pure Bi4Ti3O12 templates with aspect ratio of 5.0 were produced. Attempts to convert the Bi4Ti3O12 templates to plate-shaped Bi0.5K0.5TiO3 in molten salt were unsuccessful. Changing parameters like temperature, salt quantities and holding times did not improve the synthesis, and it was concluded that molten salt synthesis is not suitable for this reaction. Phase pure 0.75Bi0.5K0.5TiO3-0.25BiFeO3 powder was synthesized. Textured ceramics were produced by reactive-templated grain growth, where Bi4Ti3O12 templates, K2CO3 and TiO2 as precursors were added to a matrix of 0.75Bi0.5K0.5TiO3-0.25BiFeO3. Untextured reference samples were made by conventional sintering. Both textured and untextured samples were characterized with respect to phase purity, density, microstructure and ferroelectric properties. The microstructure of the textured samples was characterized by large pores probably caused by agglomerated precursors prior to sintering. The samples were phase pure and the in-situ conversion of the templates successful. The degree of texture in the textured samples was low due to inadequate orienting of the Bi4Ti3O12 templates by uniaxial pressing. Both textured and untextured samples were electrically conductive and thus not exhibiting ferroelectric properties. Further work is needed in order to assess the effect of crystallographic texture on the electromechanical properties of 0.75Bi0.5K0.5TiO3-0.25BiFeO3.