Thermal expansion properties of sintered β-eucryptite are often changed by its sintering condition, cooling condition and reheating condition.
This work intended to stabilize these unstable thermal expansion properties of sintered β-eucryptite and investigated the reheating condition.
Specimens which were sintered at the same time, were heat-treated under various conditions and the change of thermal expansion coefficient was examined. The main results were obtained as follows.
1) The most suitable heat-treatment temperature was 800°C.
2) Keeping for two hours and a half at 800°C was suitabl for stabilization of thermal expansion properties.
3) Even a sample which was stabilized by heat-treatment at 800°C for two hours and a half, varied its thermal expansion properties by quenching from the high temperature above 800°C.
4) The sample which was quenched from the high temperature above 800°C and changed its thermal expansion properties, did not turn back to its initial thermal expansion properties, even if being heat-treated two hours and a half at 800°C again.

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The anodic oxidation treatment gives a stronger adhesiveness between low melting frit and aluminum plate than the chemical treatment and no-treatment. The method of contact potential difference was used for finding out excellent adhesiveness between a lead system low melting frit and the aluminum plates which were treated by various conditions of the anodic oxidation in sulfuric acid sulution.
The concentrations of the sulfuric acid were 5, 10, 15 and 20 percent, and the anodic oxidation times were 5, 10, 15 and 20 minutes.
Electrolysis voltage between anode (aluminum plate) and cathode (carbon) was changed from 5 volt to 17.5 volt at an interval of 2.5 volt for each of the above conditions, and electrolytic bath temperature was kept at 20±3°C.
The adhesiveness of samples was found to be judged rightly from the surface potential diagram of the samples, because it has been confirmed by this experiment that the results of the surface potential diagram agree with the data of bending test.
On the other hand, the cross section of the frit and the aluminum was observed with a metal microscope, and at the same time the appearance of the aluminum surface treated was observed with an electron microscope.
From the observations, the difference of adhesiveness was explained as due to it that the various conditions of anodic oxidation brought out different states of aluminum surface.
The following conditions give the good adhesiveness.
Bath concentration 10-15%
Electrolysis time 10-15min
Voltage 7.5-12.5volt
Current density 2-4A/dm²
Electrolytic bath temp. 20±3°C
If the above conditions are kept, the thickness of the oxidized zone is about 5μ.

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Sintering of cerium oxide with or without additives in various atmospheres has been studied. As starting materials, cerous nitrate (99% purity) and cerous oxalate were used.
The conclusions were the followings:
1) The cerium oxide powder obtained at the lower calcining temperature between 400°C and 800°C was better sintered than the one obtained at the other calcining temperature. Bulk density obtained was about 6.9 which corresponds 96% of theoretical density of cerium oxide.
2) Additives used in this experiment are divided into 3 groups.
1) TiO₂, Fe₂O₃, CaO, Y₂O₃ and Cu₂ 2) NaF, Cr₂O₃ and B₂O₃, and 3) SiO₂, NiO, Al₂O₃, MgO, ZrO₂ and V₂O₅. The most effective additives for sintering were of the first group. The second effective additives were of the third group, and the worst were of the second group.
3) The grain growth of cerium oxide sintered in 1atm O₂ was the smallest among the bodies sintered in air, N₂ or Ar.
4) Appearent activation energy of sintering of cerium oxide was about 98kcal/mol, assuming that at the initial stage, the sintering of cerium oxide proceeded according to bulk diffusion model by Kingery.

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In order to make barium titanate ceramics having high dielectric constant by a process of crystallization of glass, a series of glasses with the general composition (100-x-y) BaO⋅TiO₂+xSiO₂+yAl₂O₃, in which x and y are within the range of 10 to 60 and 0 to 20 mole per cent, respectively, was investigated, especially with respect to their glass formation tendencies, crystallization behaviors during reheating and dielectric properties of their crystallized products.
The glasses were melted, in all cases, in platinum crucibles at 1450°C for one hour and formed into plate of about 2mm thick. They were crystallized by reheating up to 1100°C at a rate of 5°C/min.
The results of the experiments are summerized as follows:
1) A glass formation region was determined (cf. Fig. 1).
2) In general, crystallization of the glasses in this region starts at about 850°C, and is almost completed at 1100°C (cf. Fig. 3 and 5). The resulting crystallized products show flaws such as cracks and surface unevenness when the parent glasses contain BaO⋅TiO₂ or Al₂O₃ in excess (cf. Fig. 2).
3) Major constituents of the crystallized products are BaTiO₃ (tetragonal), BaAl₂Si₂O₈ (hexagonal), BaTiSiO₅ and some unidentified crystalline phases (cf. Table 2).
4) For the crystallized products with Al₂O₃ held constant, their dielectric constant decreases with increasing the SiO₂/BaO⋅TiO₂ mole ratio. For those with BaO⋅TiO₂ held constant, it reaches a maximum when the Al₂O₃/SiO₂ mole ratio is set to 35/65 (cf. Fig. 7). Generally, it increases with increasing the amount of barium titanate crystals separated out in the crystallized products. The composition of the crystallized product which shows a maximum dielectric constant (about 500 at 10⁶c) in the present experiments is BaO⋅TiO₂ 60, SiO₂ 26, Al₂O₃ 14 mole per cent.
5) On the basis of Bruggeman's theory the crystallized products obtained were assumed to have the structure of prophyritic mixture in which lamellar barium titanate crystals are dispersed in matrix consisting of glass phase and crystal phases of BaAl₂Si₂O₈ and BaTiSiO₅ etc. (cf. Fig. 8).

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