| About this Abstract |
| Meeting |
MS&T21: Materials Science & Technology
|
| Symposium
|
Thermodynamics of Materials in Extreme Environments
|
| Presentation Title |
Energetics of La, Nd-containing Hydroxylbastnaesite (La1-xNdxCO3OH) Solid Solutions |
| Author(s) |
Vitaliy G. Goncharov, Haylea Nisbet, Andrew Strzelecki, Chris Benmore, Hongwu Xu, Artaches Migdisov, Xiaofeng Guo |
| On-Site Speaker (Planned) |
Vitaliy G. Goncharov |
| Abstract Scope |
Hydroxylbastnaesite (LnCO3OH) is a common REE ore mineral that primarily hosts light rare-earth elements (LREE), often occurring as solid solutions in nature. To better understand the nature and the formation mechanism of such deposits, we studied hexagonal La–Nd hydroxylbastnaesite (La1–xNdxCO3OH) solid solutions (x = 0, 0.25, 0.50, 0.75, 1) by synchrotron powder X-ray diffraction, TGA-DSC-MS, and high temperature oxide melt drop solution calorimetry. Two-step decomposition pathways were confirmed for La1–xNdxCO3OH solid solutions. The enthalpies of formation of La1–x</SUB >NdxCO3OH were determined, from which the enthalpies of mixing were derived with an interaction parameter of 12.58 ± 0.16 kJ/mol, suggesting a regular solution model for the mixing of La and Nd. Lastly, we estimated the Gibbs free energy of mixing at various relevant formation temperatures, from which we demonstrated that the favorable formation of La1–xNdxCO3OH solid solution is driven by entropic effects induced by hydrothermal conditions. |