Fabrication of Ba_1−xCa_xTiO₃ Oriented Ceramics by Reactive Template Grain Growth Method Using Layered Titanate Template

Abstract

Piezoelectric performance can be improved by using crystal-axis oriented materials because piezoelectric properties of the ferroelectric materials are dependent on the crystal-axis direction. In this study, we tried to fabricate Ba_1−xCa_xTiO₃ (BCT) oriented ceramics by reactive template grain growth (RTGG) method using H_1.07Ti_1.73O₄ layered titanate (HTO) plate-like particles as the reactive template. BCT ceramics with [110]-orientation were prepared using HTO-BaCO₃-Ca(OH)₂ (HBC) and HTO-BaCO₃-Ca(OH)₂-TiO₂ (HBCT) reaction systems. The degree of orientation and the relative density of the BCT ceramics are dependent on the green sheet preparation conditions, such as dispersion condition and added binder amount, calcination temperature and starting material composition. In these reaction systems, firstly oriented BCT particles are formed by a topotactic reaction of HTO template particles with Ba and Ca matrix components, and then, BCT oriented ceramic is formed by the growth of the oriented BCT particles. BCT ceramics with higher density and higher orientation can be fabricated using HBCT reaction system than HBC reaction system, where the orientation degree is dependent strongly on the ratio of HTO template particle to TiO₂ matrix particle.