11:15 AM - 11:30 AM
[SMP42-09] Synthesis of LiNbO3-type Mg3Al2Si3O12 at 44 GPa and 2000 K using Kawai-type multianvil press with tungsten carbide anvils
Keywords:LiNbO3 structure, Rietveld refinement, High-pressure generation technique, akimotoite, pyrope, Kawai-type multianvil press
We used a 15-MN KMAP with DIA-type guide blocks carefully optimized to make a cubic compression space formed by first-stage anvils. WC anvils (TF05, Fujilloy Co., Ltd) of 1.5 mm truncation with 1.0 degree tapering were adopted for generating pressure over 40 GPa, combining a semi-sintered MgO + 5wt.%Cr2O3 octahedron as a pressure medium. Pressure at 2000 K was estimated with Al2O3 content in aluminous Brm by Liu et al. (submitted). Sintered ilmenite-type Mg3Al2Si3O12 (py-Ak) was synthesized as starting material at 26 GPa and 1200 K (Kubo and Akaogi, 2000) to minimize the pressure drop for volume change by phase transition. Sample was put in Re furnace surrounded by a LaCrO3 thermal insulator. Al2O3 rods were placed at the both end of the sample in a heater and these were separated with Re disks. A microfocus X-ray diffractometer and an FE-SEM-EDS were used to analysis phase and composition of recovered sample. Synchrotron XRD data for Rietveld analysis were collected rotating sample at ambient conditions in SPring-8 (BL10XU). Rietveld refinement of recovered sample was performed using the RIETAN-FP/VENUS package (Izumi and Momma, 2007).
R factors for structure refinement were converged to reasonable values (Rwp, RB and RF<5). Lattice parameters of this phase with space group of R3c were determined as a = 4.8196(3) Å, b = 4.8195(3) Å, c = 12.6877(8) Å, V = 255.2(1) Å3.