Immiscibility between two rutile phases in the GeO2–TiO2 system and application as a temperature sensor in high-pressure experiments


The system GeO2–TiO2 was studied experimentally at high pressure and temperature to measure the miscibility of the two components and to test its applicability as a temperature sensor in high-pressure experiments. Significant solubility between the two end-members was found, with two coexisting solid solutions at high pressure exhibiting mutual solubility that increases with temperature along a solvus. The two solid solution compositions at the solvus can be distinguished readily by X-ray diffraction. At higher temperatures, a complete solid solution exists between the two end-members. The complete solution occurs above a critical line in PT space (a critical point at each pressure). The critical point is located near 1630 °C and mole fraction \({X_{{\rm{Ti}}{{\rm{O}}_{\rm{2}}}}} = 0.57\) at 6.6 GPa and changes by 60 ± 5° per GPa in the region from 4 to 7 GPa. A model for the shape of the solvus is developed using X-ray diffraction data points from a series of quench experiments and an in situ experiment, and the model is used to estimate the thermal gradients in a Kawai-type multianvil assembly.

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Funding for this project was provided by Hyperion Materials and Technologies. Use of the COMPRES Cell Assembly Project was supported by COMPRES under NSF Cooperative Agreement EAR 1661511. Portions of this work were performed at GeoSoilEnviroCARS (GSECARS) (Sector 13), Advanced Photon Source (APS), and Argonne National Laboratory. GeoSoilEnviroCARS is supported by the National Science Foundation—Earth Sciences (EAR-1128799) and Department of Energy—Geosciences (DE-FG02-94ER14466). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract no. DE-AC02-06CH11357. We would like to thank the two reviewers for their constructive feedback. We also thank Camille Mayberry for assistance with experiments at ASU, Devin Keating at ASU for his help with taking optical images of the synthesized samples, and Yanbin Wang and Tony Yu at GSECARS for beamline support.

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Correspondence to Emil Stoyanov.

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Leinenweber, K., Stoyanov, E. & Malik, AS. Immiscibility between two rutile phases in the GeO2–TiO2 system and application as a temperature sensor in high-pressure experiments. Journal of Materials Research 34, 3368–3376 (2019).

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