[in Japanese]

View full abstract

The effects of MgF₂ addition on the formation of sintered ferrite compacts were studied. They were prepared by mixing and sintering at 1300°C for 2h in air the following compositions. MgO; 50-x, MgF₂; x, Fe₂O₃; 50mol% (x=0, 1, 4, 7, 12 and 20). During sintering almost of fluorine sublimed, its amount remained in the ferrite compacts was small, and seems to exist in ferrite lattice. A large amount of MgF₂ addition (x≥12) resulted to precipitate the foreign phase on the surface of the ferrite compacts in the form of such as MgO. Sinterability decreased practically with increasing amount of MgF₂. This decrease was attributed to a presumable decrease of cation vacancy concentration by addition of MgF₂.
The effects of MgF₂ addition on magnetic properties and crystal lattice constant of magnesium ferrite were studied. Saturation magnetization and crystal lattice constant decreased by addition of MgF₂, on the contrary, Curie temperature increased. B-H (magnetic hysteresis) characteristics also changed. Namely, magnetic flux density decreased, while coercive force increased.

View full abstract

The effect of oxygen pressure on the initial sintering of nickel oxide has been investigated by measuring the isothermal shrinkage of compacts at 690° to 780°C in the oxygen pressure range of 10^-11-1 atm. The kinetic data were analyzed with an equation for initial combined sintering of surface and volume diffusions. The oxygen partial pressure (Po₂) was controlled by using CO₂-O₂ and CO₂-CO mixtures and measured by means of a solid electrolyts cell (Ca stabilized ZrO₂). The results indicated that the volume diffusion coefficient was proportional to Po₂^1/4-1/6 in the pressure range of Po₂>10^-3 atm and almost independent of the pressure of Po₂<10^-3 atm. This range was experimentally found to agree with the impurity (monovalent) range of nickel oxide. The surface diffusion coefficient, in general, increased with Po₂ but the quantitative relation was not obtained. In this experiment, the sintering of nickel oxide was concluded to be controlled by the diffusion of trivalent nickel ions (Ni³⁺) partially associated with cation vacancies.

View full abstract

[in Japanese]

View full abstract

For application of the fabrication process that the glass powder prepared by quenching the melts of the raw materials into ice-water are cold-pressed and then fired to obtaining calcium-aluminosilicate ceramics, the compositional range of the glass formation in the system CaO-Al₂O₃-SiO₂ and the precipitation of crystals from the glasses were investigated. The results are summarized as follows;
1) The compositional range of the glass formation obtained by the quenching method as shown in Fig. 3 was wider than the range which has been reported by other workers.
2) The compositional range of the quenched glasses which could crystallize after being fired was obtained by the differential thermal analysis as shown in Fig. 3.
3) The compositional ranges from which α-wollastonite, β-wollastonite, anorthite, gehlenite and mullite crystallized by firing the quenched glasses in this system were obtained by the X-ray analysis as shown in Fig. 6.
4) In the compositional range of fairly high alumina content, there was a range from which a crystal not to be identified precipitated. It may be a metastable crystal of 3CaO⋅3Al₂O₃⋅SiO₂.

View full abstract

[in Japanese]

View full abstract

The light scattering behaviors of 73 commercial optical glasses were examined at two wavelengths and the likely contribution of scattering of the transmission losses of glass fiber optical communication system was estimated.
Most glasses showed the normal features of light scattering. That is, the scattering intensity (R₉₀) tended to be higher in the glass with higher refractive index (n) and the dissymmetry (z) could be regarded as unity. In several glasses, however, R₉₀ was much higher than that expected from the general relation between R₉₀ and n, and z was not unity showing higher intensity in the backward scattering. A glass of low refractive index and high dispersion, F 16, showed appreciably large depolarization (ρ_u). The lanthanum containing glasses of LaK-LaSK-LaF-LaSF types showed, in general, lower R₉₀ than the glasses of K-KF-LLF-LF-F-SF types, when compared at the same refractive indices.
From the comparison of the light scattering data with the direct transmission electron micrographs of thin glass films and glass fragments, it was suggested that the scattering data of some glasses showing abnormally high scattering intensity might be explained by assuming the existence of inhomogeneous regions of several ten angstrom.

View full abstract

A large positive temperature coefficient of resistivity (PTCR) in thick films of Sb-doped barium titanate was observed by treating the films with In-Hg alloy. The thick film was deposited on an alumina plate which was quietly laid in an alcoholic dispersion liquid of the semiconducting fine powder till the alcohol of dispersion medium volatized thoroughly in a dry oven. Then, the film was fired at 1280°C for 25min in air. The film thickness was controled by the weight of the powder in the dispersion liquid to give the sheet density about 0.025g/cm². Its thickness was about 50μm and its color became light grayish blue. After In-Hg alloy was rubbed smoothly as the conduction treatment on the film surface the plate was heated at 1050°C for about 25min in air. This idea to obtain good conduction properties came from the investigation of composite ceramics with texture modified.
The sheet resistivity of the film as prepared was larger than 10¹²ohm/_??_ at room temperature, while by the In-Hg treatment its resistivity became extremely small of the order of 10⁷ohm/_??_ and the PTCR effect over two orders of magnitude appeared above the Curie temperature. It should be noted that as the film thickness is 50μm the sheet resistivity of 10¹²ohm/_??_ corresponds to the apparent volume resistivity of 5×10⁹ohm⋅cm. This apparent high resistivity seems to be attributed to cracks, only around which In-Hg alloy remaining after the treatment was observed under an optical microscope. The current-voltagecharacteristic of the thick film treated with In-Hg was quite like to that of semiconducting barium titanate ceramics, while on the film as deposited a large voltage dependence of resistivity was observed.

View full abstract

Polycrystalline and transparent PbO thin films showing interference color were obtained from the 10wt% butanol solution of lead naphthenate applied on soda lime glass (slide glass) and fused silica substrates by heating above 550°C for 30minutes. The process of the film formation was examained by X-ray diffraction, electron diffraction and IR spectra.
After vaporizing of butanol at 110°C, lead naphthenate films were formed by heating below 200°C and PbO powders with the particle size of about 1μ were formed homogeneously on the substrate by the thermal decomposition of lead naphthenate film at the temperature range of 300 to 500°C. The lead naphthenate films were completely decomposed at 400°C to form a substance layer with low melting point for soda lime glass and to form lead silicate layer for fused silica at about 500°C. As the result, PbO powders were interconnected to form transparent and uniform films on there reaction products layer. The film thickness was decreased with proceeding of the reaction between PbO powders and the substrate. The film bonded firmly with the substrate as the heating temperature rises.
It may be concluded that the reaction between the PbO powders and the substrates was concerned in the formation of transparent and uniform PbO thin film.

View full abstract