title: Incorporation of Technetium into Spinel Ferrites.
abstract: Technetium (99Tc) is a problematic fission product for the long-term disposal of nuclear waste due to its long half-life, high fission yield, and to the environmental mobility of pertechnetate, the stable species in aerobic environments. One approach to preventing99Tc contamination is using sufficiently durable waste forms. We report the incorporation of technetium into a family of synthetic spinel ferrites that have environmentally durable natural analogs. A combination of X-ray diffraction, X-ray absorption fine structure spectroscopy, and chemical analysis reveals that Tc(IV) replaces Fe(III) in octahedral sites and illustrates how the resulting charge mismatch is balanced. When a large excess of divalent metal ions is present, the charge is predominantly balanced by substitution of Fe(III) by M(II). When a large excess of divalent metal ions is absent, the charge is largely balanced by creation of vacancies among the Fe(III) sites (maghemitization). In most samples, Tc is present in Tc-rich regions rather than being homogeneously distributed.
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Wayne W
authors.initials: WW
authors.lastname: Lukens
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|European Commission, Joint Research Centre, Institute for Transuranium Elements , 76125 Karlsruhe, Germany.
authors.forename: Nicola
authors.initials: N
authors.lastname: Magnani
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Tolek
authors.initials: T
authors.lastname: Tyliszczak
authors.affiliation: Geosciences Group, Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Carolyn I
authors.initials: CI
authors.lastname: Pearce
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: David K
authors.initials: DK
authors.lastname: Shuh
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D013667:Technetium / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D013667:Technetium