High-pressure high-temperature phase relations in FeTiO₃ up to 35 GPa and 1600 °C

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• 作者：M. Akaogi ; K. Abe ; H. Yusa ; T. Ishii ; T. Tajima…
• 关键词：Phase transition ; High pressure ; FeTiO3 ; Perovskite ; Lithium niobate ; FeTi2O5
• 刊名：Physics and Chemistry of Minerals
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：44
• 期：1
• 页码：63-73
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Mineralogy; Crystallography and Scattering Methods; Geochemistry; Mineral Resources;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-2021
• 卷排序：44

文摘

Phase relations in FeTiO₃ were precisely determined at 25–35 GPa and 600–1600 °C using multianvil high-pressure experiments with tungsten carbide anvils. Pressure generation up to about 36 GPa at 1600 °C was evaluated using Al₂O₃ solubility in MgSiO₃ perovskite (Pv) in the system MgSiO₃–Al₂O₃. At about 28 GPa, FeTiO₃ Pv dissociates into an assemblage of calcium titanate (CT)-type Fe₂TiO₄ + orthorhombic-I (OI)-type TiO₂ below 1200 °C. However, above 1200 °C at 28 GPa, FeTiO₃ Pv decomposes into a new, denser phase assemblage of CT-type Fe₂TiO₄ + a new compound of FeTi₂O₅. The new phase FeTi₂O₅ was recovered as an amorphous phase at 1 atm. In situ X-ray diffraction experiments at 35.1 GPa indicated that the new phase (N-p) FeTi₂O₅ has orthorhombic symmetry with cell parameters a = 8.567(2) Å, b = 5.753(1) Å and c = 5.257(1) Å. In addition, the assemblage of CT-type Fe₂TiO₄ + OI-type TiO₂ changes to FeO wüstite (Wu) + OI-type TiO₂ at about 33 GPa below 1000 °C. The phase assemblages in FeTiO₃ are denser in the order: FeTiO₃ (Pv) → 1/2Fe₂TiO₄ (CT) + 1/2TiO₂ (OI) → 1/3Fe₂TiO₄ (CT) + 1/3FeTi₂O₅ (N-p) → FeO (Wu) + TiO₂ (OI). Our results indicate that the upper stability limit of FeTiO₃ Pv is about 28 GPa at 600–1600 °C. This puts a constraint on peak shock pressure for formation of naturally discovered lithium niobate-type FeTiO₃ which was interpreted to be retrograde transition product of FeTiO₃ Pv on release of shock pressure.