About this Abstract |
| Meeting |
MS&T25: Materials Science & Technology
|
| Symposium
|
Thermodynamics of Materials in Extreme Environments
|
| Presentation Title |
Thermodynamic Stability of Hydrated Rare Earth Carbonates (Lanthanites) |
| Author(s) |
Alexandra Navrotsky |
| On-Site Speaker (Planned) |
Alexandra Navrotsky |
| Abstract Scope |
Lanthanite minerals, REE2(CO3)3•xH2O (x ~ 4 ≤ x ≤ 8) (REE = rare earth element), are important in low temperature geological settings and understanding REE fractionation and separation is essential in mineralogical and technological contexts. However, a lack of stability data has limited development of thermodynamic models in this system. This study addresses this deficiency by using room-temperature solution calorimetry and low-temperature heat capacity measurements and empirical correlations to provide new thermochemical data for lanthanites (from La to Lu). These measurements are combined with empirical fitting and extrapolation to determine thermodynamic constraints on variation in H2O content within the lanthanite system. Systematic analysis reveals a significant decrease in stability with increasing ionic radius which is consistent with strong fractionation between light and heavy REEs. This fractionation is up to 10 times larger for lanthanites than for other important REE compounds such as phosphates indicating potential for strong REE fractionation |