May 7, 2002
Conference Paper

Dissolution of A2Ti2O7 (A = Y3?, Gd3?, or Lu3?) Pyrochlore by Experiment at pH = 2, T = 90 C: Evidence for Solubility Control Using a Linear Free Energy Model

Abstract

We performed a series of dissolution experiments with well-characterized pyrochlore ceramics with the formula A2Ti2O7, where A = Y3?, Gd3?, or Lu3? in H2O- and D2O-based solutions [pH(D) = 2] at 90 C. Normalized log10 dissolution rates (g?m-2?d-1) in H2O-based solutions increase from Lu2Ti2O7 (-3.2 to -3.3) to Gd2Ti2O7 (-2.6 to -2.9), to Y2Ti2O7 (-1.9 to -2.0). Rates in D2O-based solutions are indistinguishable from rates in H2O, indicating that release of elements is probably not diffusion controlled. A recent dissolution model, based on ligand-exchange reactions, suggests that the rate of reaction should increase in inverse order of the cation field strength: Lu

Revised: March 5, 2008 | Published: May 7, 2002

Citation

Icenhower J.P., B.P. McGrail, W.J. Weber, B.D. Begg, N.J. Hess, E.A. Cordova, and J.L. Steele, et al. 2002. Dissolution of A2Ti2O7 (A = Y3?, Gd3?, or Lu3?) Pyrochlore by Experiment at pH = 2, T = 90 C: Evidence for Solubility Control Using a Linear Free Energy Model. In Scientific Basis for Nuclear Waste Management XXV, Materials Research Society Symposium Proceedings, edited by BP McGrail and GA Cragnolino, 713, 397-403 paper no. JJ6.2. Warrendale, Pennsylvania:Materials Research Society. PNNL-SA-36247.