| About this Abstract |
| Meeting |
MS&T24: Materials Science & Technology
|
| Symposium
|
Thermodynamics of Materials in Extreme Environments
|
| Presentation Title |
Thermochemistry of RE2O3-P2O5 Systems |
| Author(s) |
Elizabeth Opila, B.-C. Zhou, P.E. Hopkins, C.S. Witharamage, R. Zaman, H. Schonfeld, W. Riffe, J. Wu, L. Nahar, S Ushakov, H. Xu, Q. Hong, A. Navrotsky |
| On-Site Speaker (Planned) |
Elizabeth Opila |
| Abstract Scope |
REPO4 (RE=rare earth) compounds have recently shown promise as high temperature coatings. Compositions in the RE2O3-P2O5 systems with higher RE2O3 contents hold additional promise for high temperature applications. Y6P4O17, Y3PO7, Y8P2O17, and Y5PO10 have all been reported in three disparate phase diagrams. However, little is known about the thermodynamic stability, structures, and phase relations of these compounds. In this work, Y-rich phosphates were synthesized via laser melting and Y2O3 reactions with H3PO4. Finite-temperature thermochemical properties of the Y2O3-P2O5 system were calculated via quasi-harmonic phonon calculations for comparison to experiment. Enthalpies of formation were measured using oxide melt solution calorimetry. Definitive phase identification of synthesized materials remains difficult since the structures of many of these compounds are unknown. Transmission electron microscopy, X-ray diffraction, thermal expansion, heat capacity, and heat of formation measurements are all used to probe structure and properties of compounds in the Y-rich part of the Y2O3-P2O5 system. |