The study of the indium-containing bismuth titanate ceramics and thin films

• Main Authors: Kuo-Chang Chiang, 蔣國璋
• Other Authors: Dong-Hao Kuo
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/41659741431125759721

碩士 === 國立東華大學 === 材料科學與工程學系 === 94 === This experiment is to investigate the indium-doped Bi4Ti3O12 (BTO) and (Bi,Nd)4Ti3O12 (BNT) ceramics, and the ferroelectricity of indium-modified Bi4Ti3O12 thin films. This research was divided into two parts. The first one was the Indium-doped BTO and BNT ceramics prepared by solid-state reaction. The structure, phase components, and microstructure of BTO and BNT changed with the incorporation of indium between the Bi site and Ti site. The chemical formulation for In-BTO is [(Bi3.6+xIn0.4-x)(Ti3-xInx)Oy] with x=0, 0.1, 0.2, and 0.3, while it is [(Bi3.15+xNd0.4In0.4-x)(Ti3-xInx)Oy] with x=0, 0.1, 0.2, and 0.3 for In-BNT. In the second part, the experiment was to investigate the indium-modified Bi4Ti3O12 (BTO) ferroelectric thin films prepared by radio-frequency magnetron sputtering. We firstly studied the effect of the variation of indium component on the ferroelectricity of indium-doped Bi4Ti3O12 thin films produced with target compositions of [Bi2.45In0.35+xTi2.9Oz] at x = 0, 0.1, and 0.2. After the best performance were displayed by the target with x= 0.2, the effect of the variation of bismuth content on the ferroelectricity of indium-doped Bi4Ti3O12 thin films was studied by using the targets with the composition of [Bi2.45+yIn0.55Ti2.9Oz] at y=-0.1, 0, and 0.1. The experimental results for the In-BTO and In-BNT ceramics showed that the Bi-less Bi2Ti2O7 phase disappeared and layered perovskite Bi4Ti3O12 phase became the major phase as the formulated In content increased at the B or Ti site or as the x value increased. With the increasing of the indium content or the higher x value, the In-BTO and In-BNT grains were gradually changed from the small granules to the slab with a flat shape. According to the results of EDS analysis, the incorporation of indium almost existed in Bi2Ti2O7 phase instead of Bi4Ti3O12. If the amount of incorporating indium was large, the solid solution of the In2O3 phase with some Bi and Ti appeared. The experimental results of indium-added Bi4Ti3O12 thin films showed that the annealing temperature for the sputter-prepared indium-doped thin films was 50oC higher than those produced by the sol-gel method. The films with the best ferroelectric results were prepared by the target with a composition at x=0.2 or the formulated Bi2.45In0.55Ti2.9O11.3 target. After annealed at 650oC for 10 min in air, these films performed best and had the remanent polarization and coercive field of 7.3 µC/cm2 and 208.7 kV/cm, respectively. However the experimental results of indium-doped BTO thin films were not as expected as those films prepared by the chemical solution route. These sputtered indium-added films displayed a degraded fatigue resistance, which could be attributed to the deviations in the film composition. Further improvements in the preparation of the In-added Bi4Ti3O12 films are necessary.