An instrument for in situ observation of growth and dissolution processes of silicate crystals at elevated temperatures up to 1600°C has been newly designed. This instrument consists of a growth cell with a specially designed liquid holder, a digital temperature controller using a highly stabilized DC power unit, an optical microscopic system for in situ observation of the processes with transmitted light and a high resolution TV system for recording and displaying optical images. The stability of the temperature around the growing crystal has been improved to satisfy ±0.3°C at 1600°C in a high temperature solution of small volume (≅0.06 cm³).
This combination makes it possible to carry out the direct observations not only of growth and dissolution processes of crystals in liquid phases at high temperatures with clarity, but also of the diffusion layers and convection around growing or dissolving crystals. This system has been successfully applied to the diopside-forsterite-silica system.

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The infrared (IR) absorption patterns, and the cell dimensions of the grandite-hydrograndite series have been revealed as a function of chemistry using the materials hydrothermally synthesized at temperatures between 230 and 620°C under a pressure of 100 MPa for 5 to 76 days. They were formed from the starting materials whose compositions were written as Ca₃ (Al_1−WFe_W)₂(SiO₄)_3X(O₄H₄)_X, where W is 0.2, 0.4, 0.6, 0.8 and 1.0, and X is 0, 0.2, 0.4, 0.6, 0.8 and 1.0.
The wave numbers of nine distinct IR absorption bands between 1000 cm⁻¹ and 300 cm⁻¹ decrease by 10–70 cm⁻¹ with an increase of Fe content in the H₂O-free grandite series. The absorption band near 900 cm⁻¹ and the transmission band near 700 cm⁻¹ shift toward the higher frequency side with an increase of water and a decrease of iron. The wave numbers of two absorption bands near 600 cm⁻¹ and 520 cm⁻¹ and the transmission band near 500 cm⁻¹ decrease with increases of water and iron. The ratio of the logarithmic intensity of the transmission band near 3700 cm⁻¹ to that of the absorption one near 3660 cm⁻¹ decreases remarkably with an increase of water, while it is independent of iron content in the Al-rich (W ≤0.2) and Fe-rich (W ≥0.8) grandite-hydrograndite members. On the contrary, the cell dimension of the garnet series increases with increases of both of water and iron contents. The composition of grandite-hydrograndite series can be estimated from the IR absorption patterns and the X-ray powder diffraction data.

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Unit cell parameters of non-doped ZrO₂ (monoclinic + orthorhombic: high pressure form) and 2 mol% Y₂O₃ doped ZrO₂ (monoclinic + orthorhombic + tetragonal) samples obtained by high pressure experiments were refined, together with those of starting materials, by the technique of whole-powder-pattern fitting without reference to a structural model. The monoclinic-to-orthorhombic transformation of ZrO₂ accompanies the increase of density by 0.25 to 0.26 g/cm³. The tetragonal form has a slightly higher density than the orthorhombic form: the difference between the two phases is only 0.03 g/cm³.

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