Jiro Furuichi

A Note on the Classification of Ferroelectrics

It has been tried to classify newly discovered ferroelectrics as well as old ones according to their Curie-Weiss constants. Results have suggested that the displacive type ferroelectrics are not necessarily oxide crystals, and have also shown that small Curie-Weiss constants are not very rare in new ferroelectrics. Classification of ferroelectrics by the transition entropy is misleading in some cases.

Thermal Motion of Polyoxymethylene in Crystalline Region. I

Diffuse streaks of the X-ray diffraction fiber pattern of polyoxymethylene have been observed at room temperature. They were found to be unobservable at -170°C, the lowest temperature in this study. The existence of anisotropic diffuse streaks suggests that a special type of disorder exists in the crystal. Intensity measurements of the Bragg reflections were carried out over the temperature range from -150°C to room temperature. NMR measurements were also carried out. Comparison of NMR and X-ray results lead to the conclusion that rotational or twisting thermal motion around the chain axis begins at above -110°C in the crystalline region; the fluctuation of the atomic position around the helical axis was estimated at about 14° at room temperature.

Measurement of Microwave Dielectric Constants of Ferroelectrics Part I. Dielectric Constants of BaTiO3 Single Crystal at 3.3 KMc/s

Horner et als method of dielectric measurement at microwave region has been extended so that it can be applied for cylindrical specimens of arbitrary cross-sections with relatively high loss tangent and high permittivity. Small amount of Specimen is good enough for our method. As the first application of our method, dielectric constants of BaTiO 3 single crystal have been measured from room temperature to 170°C at a frequency of 3.3KMc/s. Above the Curie point, dielectric constants measured at 3.3KMc/s agree well with those measured at 24KMc/s by Benedict and Durand, while the loss tangents slightly above the Curie point are 0.01±0.007 in our case compared to 0.1 in the case of Benedict and Durand.

Dynamic Mechanical Properties of Polyoxymethylene III

Dynamic mechanical properties of melt grown Polyoxymethylene are studied for specimens with different lamella thicknesses and for irradiated specimens over a range of temperature from -30°C to 150°C. The apparent relaxation strength of the mechanical α-dispersion is proportional to the lamella thickness. This result qualitatively satisfies the requirements of Okanos theory of crystalline dispersion. The apparent relaxation strength of the α-dispersion for irradiated specimens increases with increasing irradiation dose. This behavior is not due to the growth of lamella thickness with irradiation, but due to other effects, such as the occurrence of lattice defects in crystallites by irradiation. Thus it is impossible to explain this behavior in terms of Okanos theory. The apparent activation energy of the α-dispersion does not change with γ-irradiation, which indication, which indicates that the irradiation does not essentially influence the molecular mechanism of the dispersion.

Effects of γ-Rays on Aqueous Solutions of Synthetic Polymers

Observations were made on the effects of gamma rays from Co/sup 60/ on aqueous solutions of synthetic polyelectrolyte Na-CMC. According to ultracentrifugal figures of concentrated solutions, Na-CMC seems to be a mixture of two groups, one of which has a larger molecular weight than the other. Decreases of specific viscosity due to irradiation are tabulated. Changes of molecular weights calculated from the intrinsic viscosity and those of ultracentrifugal coefficients are also tabulated. At low temperatures, the conductivity of the irradiated solution is greater. (A.C.)

Studies of High Polymers by Radioactive Method (II) Self-diffusion of Polystyrene in Its Dilute Solution

Self-diffusion of high polymer in dilute solution was studied by use of C 14 -labelled polystyrene. Especially the dependence of the self-diffusion coefficient of polystyrene upon its molecular weight was determined. Then, from the results, the molecular extension, the shielding ratio, and other molecular quantities of polystyrene molecule in the dilute solution were calculated by use of the diffusion theory of Debye and Bueche, and compared with the data obtained by other methods.