The structure of Cs2ZrSi3O9, which was synthesized using a sol gel method, was determined from Rietveld refinement of experimental X-ray powder diffraction data. The refinement confirmed that this compound is isostructural with wadeite: its structure is hexagonal (space group P63/m), and its lattice parameters are a=7.2303(2) Angstrom, c=10.2682(4) Angstrom. The aqueous durability of Cs2ZrSi3O9 measured using standardized leach tests varied depending on solution conditions. In standardized PCT and MCC-1 leach tests, as well as in buffered (pH=7) solutions, the aqueous durability was high with 7 day leach rates less than 1.2 x 10 -4 g/m2 day. However, in unsaturated, unbuffered solutions with a pH between 9 and 10, the durablity of this material to retain Cs in aqueous environments can be explained by its condensed ring structure in which the channel size openings are smaller that the diameter of a Cs ion. However, dissolution of the network silicate occurs at high pH, resulting in the release of Cs.
Revised: January 12, 2012 |
Published: January 15, 2001
Balmer M.L., Y. Su, H. Xu, E.R. Bitten, D.E. McCready, and A. Navrotsky. 2001.Synthesis, Structure Determination, and Aqueous Durability of Cs2ZrSi3O9.Journal of the American Ceramic Society 84, no. 1:153-160.PNNL-SA-32470.