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The effect of polymorphic structure on the structural and chemical stability of yttrium disilicates

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Published/Copyright: April 2, 2015
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American Mineralogist
From the journal American Mineralogist Volume 96 Issue 10

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 stability range of yttrium disilicates in response to changes in pH. The α, β, γ, and δ 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 δ 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.

Keywords : Yttrium disilicates; sol-gel processes; polymorphism; leaching rate; nuclear applications
Received: 2010-7-24
Accepted: 2011-6-9
Published Online: 2015-4-2
Published in Print: 2011-10-1

© 2015 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am.2011.3659
Keywords for this article
Yttrium disilicates; sol-gel processes; polymorphism; leaching rate; nuclear applications

Articles in the same Issue

  1. Compressional wave velocity measurements through sandy sediments containing methane hydrate
  2. The turquoise-chalcosiderite Cu(Al,Fe3+)6(PO4)4(OH)8·4H2O solid-solution series: A Mössbauer spectroscopy, XRD, EMPA, and FTIR study
  3. Variability in sepiolite: Diffraction studies
  4. Rankamaite from the Urubu pegmatite, Itinga, Minas Gerais, Brazil: Crystal chemistry and Rietveld refinement
  5. Zeolitic-type Brønsted-Lowry sites distribution imaged on clinochlore
  6. Thermodynamic properties of alloys of gold-74/palladium-26 with variable amounts of iron and the use of Au-Pd-Fe alloys as containers for experimental petrology
  7. first-principles investigation of hydrous defects and IR frequencies in forsterite: The case for Si vacancies
  8. Estimating compositions of natural ringwoodite in the heavily shocked Grove Mountains 052049 meteorite from Raman spectra
  9. Phase stability and compression study of (Fe0.89,Ni0.11)3S up to pressure of the Earth’s core
  10. The compression pathway of quartz
  11. Experimental investigations into the silicification of olivine: Implications for the reaction mechanism and acid neutralization
  12. The effect of polymorphic structure on the structural and chemical stability of yttrium disilicates
  13. Diffusion in yttrium aluminium garnet at the nanometer-scale: Insight into the effective grain boundary width
  14. Elasticity and anisotropy of Fe3C at high pressures
  15. Raman spectroscopy of titanomagnetites: Calibration of the intensity of Raman peaks as a sensitive indicator for their Ti content
  16. Experimental determination of stability relations between monazite, fluorapatite, allanite, and REE-epidote as a function of pressure, temperature, and fluid composition
  17. Quantum-mechanical calculations of the Raman spectra of Mg- and Fe-cordierite
  18. Coarsening kinetics of coexisting peristerite and film microperthite over 104 to 105 years
  19. Local structure variations observed in orthoenstatite at high pressures
  20. Static disorders of atoms and experimental determination of Debye temperature in pyrope: Low- and high-temperature single-crystal X-ray diffraction study
  21. Effect of hydration on the single-crystal elasticity of Fe-bearing wadsleyite to 12 GPa
  22. Early Proterozoic weathering processes under low O2 conditions reconstructed from a 2.45 Ga paleosol in Pronto, Canada
  23. Eliseevite, Na1.5Li[Ti2Si4O12.5(OH)1.5]∙2H2O, a new microporous titanosilicate from the Lovozero alkaline massif (Kola Peninsula, Russia)
  24. The development of shape- and crystallographic-preferred orientation in CaPtO3 post-perovskite deformed in pure shear
  25. Amorphous Materials. An experimental study of phosphorous and aluminosilicate speciation in and partitioning between aqueous fluids and silicate melts determined in-situ at high temperature and pressure
  26. Letter. Differential degassing of H2O, Cl, F, and S: Potential effects on lunar apatite
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