Thermal expansivity of geikielite and ilmenite utilizing in-situ synchrotron X-ray diffraction at high temperature

• 作者: OA Jiamei Song Dawei Fan Shijie Huang Shanrong Zhang Mengzeng Wu Wei Chen Wenge Zhou .Key Laboratory of High-Temperature and High-Pressure Study of the Earth's Interior Institute of Geochemistry Chinese Academy of Sciences .University of Chinese Academy of Sciences .Guizhou Polytechnic of Construction
• 来源期刊: 地球化学学报(英文）
• 学科: 地球科学
• 年，卷（期）: 2025,（6）
• 页码范围: 28-37
• 页数: 10页
• 语种: 中文

摘要

The unit-cell parameters and volumes of geikielite（MgTiO3） and ilmenite（FeTiO3） were investigated at high temperatures up to 700 K and ambient pressure,using in-situ angle-dispersive synchrotron X-ray diffraction.No phase transition was detected over the experimental temperature range.Using（Berman in J Petrol29:445-522,1988.10.1093/petrology/29.2.445） equations to fit the temperature-volume data,the volumetric thermal expansion coefficients at ambient conditions(αV0) of MgTiO3 and FeTiO3 were obtained as follows:2.55（6）×10-5 K-1 and 2.82（10）×10-5 K-1,respectively.We infer that the larger effective ionic radius of Fe2+（Ⅵ）(0.78 A) than that of Mg2+（Ⅵ）(0.72 ?) renders FeTiO3has a larger volumetric thermal expansivity than MgTiO3.Simultaneously,the refined axial thermal expansion coefficients under ambient conditions are αa0=0.74（3）×10-5 K-1 and αc0=1.08（5）×10-5 K-1 for the aaxis and c-axis of MgTiO3,respectively,and αa0=0.95（5）×10-5 K-1 and αc0=0.92（12）×10-5 K-1 for the aaxis and c-axis of FeTiO3,respectively.The axial thermal expansivity of MgTiO3 is anisotropic,but that of FeTiO3 is nearly isotropic.We infer that the main reason for the different axial thermal expansivity between MgTiO3 and FeTiO3 is that the thermal expansion mode of the Mg-O bond in MgTiO3 is different from that of the Fe-O bonds in FeTiO3.