The study of the materials of the lower mantle by a laser heated diamond anvil cell and analytical electron microscopy

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In this study, the YLF laser-heated diamond anvil cell (DAC) experiments at up to 100 GPa and 3000 K and analytical transmission electron microscopy (ATEM) using the ultrathin foils prepared by ultramicrotomy were developed. By the combined method of a laser-heated DAC, synchrotron X-ray diffraction and ATEM, the following results were obtained.1) High pressure syntheses of CaMgSi_2O_6-CaFeSi_2O_6 pyroxene at 30-80 Gpa and 1700-2200 K and analyses of the samples revealed that the Ca solubility in MgSiO_3 perovskite was about 1-2 mole % at 30 Gpa in the CaMgSi_2O_6 end and does not seem to change with increasing the Fe content or pressure, while the Mg solubility in CaSiO_3 perovskite was about 4 mole % at 30 Gpa in the CaMgSi_2O_6 end but the (Mg,Fe) solubility in CaSiO_3 perovskite significantly increased up to 20-30 mole % with increasing the Fe content and pressure.2) High pressure syntheses of (Mg,Fe)SiO_3-Al_2O_3 gel at 30-60 GPa and 1800-2000 K and analyses of the samples showed that the Fe solubility in (Mg,Fe)SiO_3 perovskite increased with increasing the Al content in perovskite, indicating the formation of the endmember Fe^<3+>Al^<3+>O_3 in perovskite.3) High pressure syntheses of CaSiO_3-CaTiO_3 glass at 30 Gpa and 1800 K and analyses of the samples showed that the Ti substitution for Si in CaSiO_3 perovakite produced doubling of a unit cell axis, resulting in a double perovskite-like structure in the intermediate composition of this system. This structure is face-centered cubic at high pressure and high temperature, but it inverts to a lower symmetry structure during cooling.