Investigations have been made on the formation of the ferrites prepared by solid-state reaction of the mixtures of the ratios 1:1 ZnO:Fe₂O₃, 1:1 MnCO₃:Fe₂O₃, 1:1:2ZnO:MnCO₃:Fe₂O₃, fired under different schedules.
X-ray diffraction patterns were obtained for the polycrystalline ferrites of spinel structure formed at various firing temperatures. It was confirmed that zinc ferrite phase was formed when the firing took place in air at below 800°C, while manganese ferrite phase appeared at 1150°C.
Prefiring at the temperature of the formation of zinc-manganese ferrite (about 800°C) can be carried out in air. The final firing should be done in air at the temperatures higher than 1150°C to promote good crystallization. The temperature should not be too high, since over-sintering leads to the too much shrinkage, bending etc., which are prohibitive for producing ferrites of exact dimensions.

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Experiments were made to prepare yttrium iron garnet (Y₃Fe₅O₁₂) single crystals in molten YF₃-PbF₂ solutions. The solubilities of Y₂O₃ in YF₃ were obtained by differential thermal analysis, and those of Fe₂O₃ in PbF₂ in air by chemical analysis of quenched specimens.
Mixtures of Y₂O₃ and Fe₂O₃ were dissolved in YF₃-PbF₂ solutions at 1300°-1350°C and then the solutions were cooled at the rate of 4-10°C/hr to prepare yttrium iron garnet single crystals.
Spacings of these crystals were compared with those of crystals prepared by the other methods.

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The high temperature powder X-ray diffraction methods and the differential thermal analysis were applied in studying the modifications, α, α′, β of 2CaO⋅SiO₂, which covered the temperature range 25°-1550°C.
These methods have proved to be able to determine distinctly the inversion temperatures during both in the heating as well as in the cooling processes with the following results:
A. Heating process.
1) γ-form was stable in the temperatures from 25° to 740°C, giving the X-ray pattern similar to that of 2MgO⋅SiO₂.
2) α′-form was stable in the temperatures from 900° to 1450°C, giving the X-ray pattern similar to that of β-K₂SO₄, and the cell dimensions a=6.883, b=5.605, and c=9.543 a. u. at 1300°C.
3) α-form was stable above 1490°C, giving X-ray pattern similar to that of α-K₂SO₄ (glaserite), and the cell dimensions a=5.27, and c=5.11 a. u. at 1500°C.
B. Cooling process.
4) Inversion α→α′-form occured between 1450° and 1390°C. The intensity of X-ray diffraction of α′-form produced by the inversion of α was slightly different from that produced by heating γ-form. The difference, however, faded away when passing 1190°-1150°C.
5) The inversion from α to β-form occured at 690°C. The X-ray pattern of β-form is the same with that stabilized to room temperature by adding stabilizers, Cr₂O₃, B₂O₃. The cell dimensions at 550°C were a=5.558, b=6.823 and c=11.261 a. u., ∠β=123° 11′.
6) The change from β- to γ-form occured at 450°C accompanying the dusting. The unit cells of α, α′ and β shown in this paper were P3ml, Pnma and P2₁/c, respectively following the International Tables for X-ray Crystallography (1952).

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After the pattern of Buss (Glas techn. Ber., 30, 145 (1959)) a simple high temperature microscope was constructed, which, although with low magnification, was possible to follow after the glass melting process up to about 1450°C by continuous observation.
As the equipment has proved to be useful for present purpose a series of studies was made on the effect of the minor ingradients upon the melting process Na₂O-CaO-MgO-SiO₂ glass by observing the evolution of bubbles, change of the fluidity as well as the velocity of dissolution of quartz grains.
The comparative test of 12 additional agents was carried out with a result showing that CaF₂, Li₂CO₃ and H₃BO₃ were effective in the case of the maximum holding temperature of 1400°C.

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