title: A Potential Wasteform for Cs Immobilization: Synthesis, Structure Determination, and Aqueous Durability of Cs2TiNb6O18.
abstract: Cs2TiNb6O18is a potential ceramic wasteform for the long-term immobilization of radioactive cesium. Cs2TiNb6O18was synthesized using the aqueous precursor method and a solid-state reaction, and its crystal structure was determined from the Rietveld refinement of synchrotron X-ray and neutron powder diffraction data. The structure is a pyrochlore analogue, space group P3̅m1 with Cs in 9-fold coordination. The calculated bond valence sum from analysis of neutron diffraction data of 0.84 and high coordination number suggest that Cs has a strong bonding environment. The chemical aqueous durability was investigated using the MCC-1 and PCT-B standard test methods. The measured Cs leach rates of 3.8 × 10-3and 2.1 × 10-3g m-2day-1obtained via the MCC-1 and PCT-B methods, respectively, demonstrate good promise of a safe long-term immobilization material comparable to, if not better than, hollandite-the material in the multiphase titanate ceramics (Synroc) targeted for cesium sequestration.
authors.affiliation: School of Chemistry, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom.
authors.forename: Tzu-Yu
authors.initials: TY
authors.lastname: Chen
authors.affiliation: National Nuclear Laboratory , Workington, Cumbria CA14 3YQ, United Kingdom.
authors.forename: Ewan R
authors.initials: ER
authors.lastname: Maddrell
authors.affiliation: Department of Materials Science and Engineering, University of Sheffield , Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, United Kingdom.
authors.forename: Neil C
authors.initials: NC
authors.lastname: Hyatt
authors.affiliation: School of Chemistry, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom.
authors.forename: Joseph A
authors.identifier: http://orcid.org/0000-0001-9978-6530
authors.initials: JA
authors.lastname: Hriljac