Shizuo Miyake

On the Phase Transition in Cuprous Iodide

The phase transition and the crystal structures of cuprous iodide (CuI) have been studied by the X-ray and calorimetric measurement Two phase transitions at 369°C and 407°C were found and the corresponding energy and entropy changes were estimated from the specific heattemperature curve. The crystal lattice of γ, β and α-phases were determined to be the cubip (ZnS type), hexagonal (ZnO type) and cubic, respectively, by the X-ray powder method. The intensity change with temperature was measured in detail by a new method by which the begins temperature factor can be taken into account more exactly. From this measurement, it was found that the crystal structure of this substance begins to change anomalously already at about 200°C, and finally transforms into the high temperature form having an average structure. That is to say, there are some metastable positions around every copper position of the low temperature form and the probability of finding the Cu-atoms in these positions gradually increases with te...

X-ray Studies on the Structures of Solid Solutions NaCl-CaCl2 I. Main Results and General Considerations

Stationary X-ray diffraction patterns from transparent single crystals of solid solutions of NaCl dissolved with a few per cent of CaCl 2 show a number of diffuse spots. Their displacements with the change of the direction of incident X-rays reveal the existence of several kinds of rods in reciprocal space. Among them, the rods running along and rows are most remarkable. The appearance of these rods are considered as the result of the formation of thin plate-like precipitates in the matrix because of the homogeneous solid solutions being unstable at room temperatures. The precipitates may be the places where Ca ++ ions replacing Na + ions, and vacancies of Na + sites, are locally concentrated. It was shown, by a general consideration, that the plate-like precipitate responsible for or rods is likely composed of an assembly of anti-phase, domains of super structures.

Transition from Dynamical to Kinematical Intensities of Electron Diffraction by Crystals

The transition from dynamical to kinematical intensities of electron diffraction from crystals with the change of wave-length of electrons and crystal thickness is theoretically discussed. It is pointed out that the usual treatment of the dynamical theory by the two-wave approximation fails to apply in the range of very short wave-length and small crystal thickness, even with the correction of the dynamical Fourier potential, so that the advent of some convenient treatments taking account of many reflected waves is of essential necessity for consideration of the transition of reflected intensities. It is pointed out, at the same time, that the application of the pseudo-kinematical theory using the complex atomic scattering amplitude calculated on isolated atoms is not permissible in the case of electron diffraction by crystals even for their thinnest limit.