Goro Honjo

Electron Optical Studies of Barium Titanate Single Crystal Films

Thin single crystal films of barium titanate prepared by chemical thinning of single crystal plates are studied by transmission electron microscopy and electron diffraction. The films as thin as 1000 A are found to have the same lattice parameters as the bulk crystals, giving no evidence for the existence of the anomalous surface layer proposed by Kanzig et al. The surface of barium titanate is found to change substantially when heated above 500°C in air and vacuo, invalidating their evidence for an unusually high Curie temperature of their anomalous surface layer. Ferroelectric 90° and 180° domains are observed by electron microscopy. The contrast of 90° domains is simple diffraction contrast. The contrast of 180° domains is due to the failure of Friedels law, which is known to be possible to take place in electron diffraction by dynamical diffraction effect. Dislocations, tracks of fission fragments from uranium and their interaction with domains are observed.

Diffuse Streak Diffraction Patterns from Single Crystals I. General Discussion and Aspects of Electron Diffraction Diffuse Streak Patterns

Diffuse streak patterns from single crystals which have become to be noticed very recently in electron diffraction are identified with the “non-radial” streak patterns in X-ray diffraction and their description in terms of parallel wall distribution of intensity weight along low index reciprocal net planes is discussed. Evidences for the description in electron diffraction patterns from silicon, germanium, aluminium. gold, iron, sodium and potassium chlorides and barium titanate are illustrated. An assumption of linear chain scatterers consisting of a small number of nearest neighbour atoms shifted from their regular positions is shown to be able to reproduce the characteristic features of the streak patterns from diamond structure and simple face centred cubic structure. Applicability of similar assumptions to the other cases is suggested.

Low Temperature Specimen Method for Electron Diffraction and Electron Microscopy

Techniques of low temperature specimen method for electron diffraction and electron microscopy were developed. Convenient low temperature specimen holders were constructed with a sufficient number of freedoms to adjust specimen settings for various observations. The temperature of specimen support could be varied within a range from liquid nitrogen temperature to +200°C. Contaminations of specimen caused by condensation of residual vapours, which usually occur considerably below -80°C, were practically eliminated by improving the vacuum of the apparatus and by the use of a special shield around specimen. Results of preliminary studies on ice and mercury were briefly described: For ice, the contribution of hydrogen atoms to the diffraction pattern of ice was recognized; for mercury, the solid-liquid phase transition was studied by electron diffraction and the growth of hair-like mercury crystallites was observed by electron microscopy.

Fine Structure due to Refraction Effect in Electron Diffraction Pattern of Powder Sample:Part II. Multiple Structures due to Double Refraction given by Randomly Oriented Smoke Particles of Magnesium and Cadmium Oxide

Fine structures composed of sets of doublets as expected by the double refraction effect, an effect concluded by the dynamical theory of electron diffraction, are studied in details for reflexions given by individual smoke particles of magnesium and cadmium oxides having random orientations. The configurations of doublets vary according not only to the azimuths of the crystallites but also to the angles of deviations from Bragg condition, namely, the errors of resonance of Bragg reflexions. By determining these two parameters from the configuration, the mean and periodic terms of the Fourier expansion of the inner potentials of the crystals are obtained from the inter-doublets and intra-doublets separations in the fine structures. The results show a reasonable agreement with the theoretical values. The intensity anomaly of the double refraction effect, suggested in Part I, are found to be a general phenomenon. It is observed that between the two spots of a doublet, that of larger deviation is always weake...

Electron Diffraction Studies on Oxide Films formed on Metals and Alloys Part 2. Selective Oxidation of Alloys

Surface oxidation products on various alloys due to varying oxidizing conditions within the range of 300–900°C for temperature and 10 -4 –760 mmHg. for air pressure are studied by the electron diffraction method. Alloys studied are copper alloys containing 0.3 % Be, 0.5 % Al, 0.1 % Mg, 7 % Mn and 7 % Ni and that of iron with 13 % Al respectively. The selective oxidation or the phenomenon that the baser component of alloy is oxidized selectively in spite of its much lower content in the mother alloy than the other was found to occur generally in these alloys when the air pressure is sufficiently low and the temperature is high enough. High yield of the secondary electron emission of Be-Cu alloy is concluded to be due to the selective oxidation product BeO having a particular orientation grown on this alloy. An unknown oxide of Ni of a spinel type structure is found on 7 % Ni-Cu alloy.

Fine Structure Due to Refraction Effect in Electron Diffraction Pattern of Powder Sample:Part I. Fine Structure given by Magnesium and Cadmium Oxide Smoke having a Fibrous Orientation

Fine structures due to refraction effect in electron diffraction patterns of cubic magnesium and cadmium oxides are studied when the sample have a fibrous orientation around [001] axis and the electron incidence is nearly perpendicular to the axis. In the case of magnesium oxide, most of the reflexions split into doublets corresponding to the ordinary refraction effect due to a mean inner potential of about 15∼16 volts; (002) reflexion, however, splits into quartet corresponding to the double refraction effect, which was formerly pointed out by Sturkey, the separation of which is also in accordance with the theoretical expectation. The intensities of the two spots corresponding to a double refraction are found to be remarkably different; the spot of larger deviation is weaker than that of smaller deviation. In the.case of cadmium oxide, though the fine structures of the fibrous reflexion are less apparent than in the case of magnesium oxide, it is noted the fact that the (111) reflexion splits only into d...

Interference Fringes in Electron Micrographs of Magnesium Oxide

The striations, or so called equal thickness fringes, appearing in electron micrographs of magnesium oxide, have been studied in detail. It was found that the spacing of the striations ranges from 50 to several hundred Angstroms, depending on the index of reflexion, azimuth, and glancing angle. The explanation of the striations is given by the dynamical theory applied to a wedge-shaped crystal. Calculated spacings of the striations as a function of azimuth and glancing angle are compared with observed values, giving fairly good agreement. Some newly found crystal shapes other than cubic and the effect of simultaneous reflexions on the striations are also described.