Abstract
Under pressure and temperature conditions like those found in deep geological repositories (DGRs), rare-earth cations may react with silicates to form rare-earth disilicates. This study establishes the stabil-ity range of yttrium disilicates in response to changes in pH. The a, ß, ?, and d polymorphs of Y2Si2O7 were synthesized by the sol-gel process at temperatures between 1100 and 1650 °C and subjected to pHstat leaching tests. By measuring the Y and Si leaching rates and monitoring the transformation of the crystalline and amorphous phases, we showed that yttrium disilicates were stable at pH > 5. At pH < 5, the pH stability sequence was consistent with the temperature-dependent stabilities of Y2Si2O7 phases, with the d polymorph showing the lowest leaching rates. Because rare-earth compounds can be used as a proxy for analogous actinide hosts, the results of this study can be used to predict the performance of engineered barriers in DGR.
Original language | English |
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Pages (from-to) | 1512-1520 |
Number of pages | 9 |
Journal | American Mineralogist |
Volume | 96 |
Issue number | 10 |
DOIs | |
Publication status | Published - Oct 2011 |
Externally published | Yes |
Keywords
- Leaching rate
- Nuclear applications
- Polymorphism
- Sol-gel processes
- Yttrium disilicates
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology