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Two types of imaging methods in high resolution transmission electron microscopy, which give the images of atoms at the atomic positions in crystals containing defects, are presented. Using one of the methods, atomic arrangements of partial dislocations, intrinsic and extrinsic stacking faults, sessile dislocations formed by the interaction of two partial dislocations, and coherent and incoherent twin boundaries in gold thin crystals have been observed. Dynamic observations using TV systems have been carried out on the movement of atoms accompanying the formation, the movement and disappearance of stacking faults and twins, and their interaction.

Using the aberration-free focus (AFF) imaging condition in tilted illumination and by adjusting the thickness of gold crystals to optimum values, the electron-microscope images of gold atoms in perfect crystals are formed at the correct positions of atoms with a resolution higher than the theoretical resolution limit in normal operation. This method is applied to observe the images of atoms in gold crystals containing planar defects such as twin boundaries and stacking faults. The observed contrast of the images is compared with theoretical calculations based on both the HowieWhelan theory of electron diffraction in many-beam form and an electron image-formation theory. The agreement between observations and theoretical cap culations is fairly good.

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The microstructural changes in the initial stage of a conversion process of α-tricalcium phosphate [α-Ca3(PO4)2] (α-TCP) to hydroxyapatite [Ca10(PO4)6(OH)2] (HAp) by the hydrolysis method were investigated by transmission electron microscopy (TEM). To investigate the microstructural changes that take place during the conversion process, we prepared two types of α-TCP specimens for TEM: α-TCP powder and sintered α-TCP thin film. According to our results, the microstructural changes can be summarized as follows. At first, the surface of the α-TCP was covered with an amorphous calcium phosphate layer, resulting from hydration or the dissolution of α-TCP. Subsequently, the nucleation of HAp occurred on the amorphous layer, and then dendritic structures appeared on the layer. Thereafter, the dendritic structures would grow into needlelike fine HAp crystals.