CHARACTERIZATION OF BaTiO3 POWDERS BY TRANSMISSION ELECTRON MICROSCOPY AND SCANNING TRANSMISSION ELECTRON MICROSCOPY

摘要

Barium titanate (BaTiOs) is the basic material of ceramic capacitors. Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) have been applied to investigate the microstructure of BaTiO3 powders. Either a focused-ion-beam (FIB) cutting technique or a low angle Ar-ion beam milling technique has been successfully used to prepare TEM specimens of BaTiO3 powder cross-sections. In this paper, examples of some observations have been shown. The mechanism of the solid state synthesis of fine BaTiO3 powders has been studied. The reaction process can be observed as visual images. The surface modification of BaTiO3 particles (0.2μm size) by leaching was also investigated. The leaching was performed using a hydrochloric acid solution (0.01N HC1) until a Ba/Ti ratio reached to 0.955. In this case, the formation of an amorphous Ti-O layer was confirmed by. high-resolution electron microscopy (HRTEM). The surface modification, however, was found to have no significant influence on the overall crystallinity of the powders. In recent years the modifying techniques of the BaTiO3 surface have made rapid progress and the TEM or STEM observations has been indispensable to investigate the surface structure.