Influence of post-annealing treatment on dielectric and ferroelectric properties of dense BaTiO₃ ceramics prepared by solvothermal solidification method

Abstract

We investigated an influence of post-annealing treatment on dielectric and ferroelectric properties of BaTiO₃ (BT) ceramics with a high relative density of around 90% prepared by a solvothermal solidification method at 200°C. In the solvothermal solidification method, green compacts consisting of TiO₂ nanoparticles were converted into the BT ceramics in Ba(OH)₂ ethanol/water reaction solutions, and the BT formation reaction accompanied by a volume increase was utilized for densification of the BT ceramics. By reducing mixing ratios of organic binder in formation of TiO₂ green compacts, the relative density of the BT ceramics reached to around 90% after the solvothermal treatment at 200°C for 36 h. The as-prepared BT ceramics with pseudo-cubic symmetry show the lower dielectric constant of around 500 in spite of the high relative density due possibly to the size effect and/or incorporation of hydroxyl groups in crystal lattices. Therefore, we tried to enhance the dielectric constant by the post-annealing treatment at 500–1200°C for 2 h in air. Although the BT ceramics showed the pseudo-cubic symmetry even after the post-annealing at 500–1100°C, the dielectric constant increases with the post-annealing temperature and the polarization–electric field (P–E) loops and strain–electric field (S–E) curves show the improved ferroelectric behavior. The post-annealing treatment was effective to enhance the electrical properties of the BT ceramics prepared by the solvothermal solidification method owing mainly to facilitating grain growth. The dielectric constant of over 1000 could be obtained by annealing at 800°C.