Raman spectroscopic studies were made for MgSiO₃ perovskite, MgSiO₃ garnet, and majorite with compositions of En₆₀Py₄₀ and En₈₀Py₂₀ synthesized at high pressure and high temperature. The frequencies of eight Raman active modes of MgSiO₃ perovskite were measured at one atmosphere. Three modes with the frequencies, 388, 600 and 937cm⁻¹, were observed for the first time. The frequency of Raman bands of the majorite solid solutions has very weak compositional dependence.
The pressure dependence of the two Raman peaks (602 and 932 cm⁻¹ at one atmosphere) of MgSiO₃ garnet was measured up to 26.3GPa using diamond anvill cell; these peaks correspond to the SiO₄ internal vibration modes. The Raman frequencies increase lineary with increasing pressure. The mode Grüneisen parameters of these modes are deduced as 0.80 and 0.79.

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The structures of Mg₃Al₂Si₃O₁₂ and Ca₃Al₂Si₃O₁₂ glasses were investigated by means of the radial distribution function (RDF) analysis based on X-ray diffraction data. The Al and Si atoms in these glasses are essentially in four-fold coordination. The T–O (T=A1 and Si) distance of Mg₃Al₂Si₃O₁₂ glass (1.68Å) estimated from the peak position of radial distribution function curve is almost equal to that of Ca₃Al₂Si₃O₁₂ glass (1.70Å). These T–O distances are consistent with the common average T–O distance in AlO₄ and SiO₄ tetrahedra. Mg–O distance in Mg₃Al₂Si₃O₁₂ glass is 2.1Å and coordination number of Mg atom is 4.8. These values are smaller than those in pyroxene and pyrope crystals. Ca–O distances in Ca₃Al₂Si₃O₁₂ glass is 2.4Å and coordination number of Ca atom is 7.1–7.4. These values are in conformity with those obtained in grossular and diopside crystals. The short range structures of Mg₃Al₂Si₃O₁₂ and Ca₃Al₂Si₃O₁₂ glasses, the oxygen coordination around T, Mg, and Ca atoms resemble those of MgSiO₃ and CaSiO₃ glasses, respectively. Especially, the G(r) curve of Mg₃Al₂Si₃O₁₂ glass is very similar to that of MgSiO₃ glass.

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Phase transition from orthoenstatite (Pbca-form) to high-clinoenstatite (C2⁄c-form) was first found by the in situ observation at above ∼1200°C under a transmission electron microscope [TEM]. Upon heating the orthoenstatite specimens, (100) stacking faults abruptly appeared at above ∼1100°C, and high-clinoenstatite was designated in the diffraction pattern at above ∼1200°C. The transition from orthoenstatite (O) to high-clinoenstatite (C) occurred with the topotactic relations of a_o⁄⁄a_c^*,b_o⁄⁄b_c, and c_o⁄⁄c_c. These facts indicate that the (100) intergrowth of high-clinoenstatite occurred on a very fine scale in the parent phase of orthoenstatite at high temperatures.

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Three types of hydroxyapatite (HAp) were prepared by adding an H₃PO₄ solution into a Ca(OH)₂ suspension at room temperature, 50°C and 80°C. The crystals had plate-like shape elongated along the c-axis. The CO₂ content and adsorbed water decreased with the elevating reaction temperature. The crystal grew approximately 50 nm below 50°C and the grain grew nearly 200 nm at 80°C. The secondary particle size prepared at each temperature was in the order: 80°C << room temperature <50°C. The particle size distributions showed that the 50vol% sizes of HAp prepared at room temperature and 50°C were 4.2 and 7.5 μm, respectively, and that they aggregated strongly. In the case of HAp prepared at 80°C, the particles consisted mainly submicron grains (0.4 μm in 50vol%-size) and were hard to aggregate.

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