title: Chemical Trends in Solid Alkali Pertechnetates.
abstract: Insight into the solid-state chemistry of pure technetium-99 (99Tc) oxides is required in the development of a robust immobilization and disposal system for nuclear waste stemming from the radiopharmaceutical industry, from the production of nuclear weapons, and from spent nuclear fuel. However, because of its radiotoxicity and the subsequent requirement of special facilities and handling procedures for research, only a few studies have been completed, many of which are over 20 years old. In this study, we report the synthesis of pure alkali pertechnetates (sodium, potassium, rubidium, and cesium) and analysis of these compounds by Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), solid-state nuclear magnetic resonance (static and magic angle spinning), and neutron diffraction. The structures and spectral signatures of these compounds will aid in refining the understanding of99Tc incorporation into and release from nuclear waste glasses. NaTcO4shows aspects of the relatively higher electronegativity of the Na atom, resulting in large distortions of the pertechnetate tetrahedron and deshielding of the99Tc nucleus relative to the aqueous TcO4-. At the other extreme, the large Cs and Rb atoms interact only weakly with the pertechnetate, have closer to perfect tetrahedral symmetry at the Tc atom, and have very similar vibrational spectra, even though the crystal structure of CsTcO4is orthorhombic while that of RbTcO4is tetragonal. Further trends are observed in the cell volume and quadrupolar coupling constant.
authors.affiliation: Department of Chemistry, Washington State University , Pullman, Washington 99164, United States.|Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Jamie
authors.initials: J
authors.lastname: Weaver
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Chuck Z
authors.initials: CZ
authors.lastname: Soderquist
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Nancy M
authors.identifier: http://orcid.org/0000-0002-9643-6794
authors.initials: NM
authors.lastname: Washton
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Lipton
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Gassman
authors.affiliation: Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Wayne W
authors.identifier: http://orcid.org/0000-0002-0796-7631
authors.initials: WW
authors.lastname: Lukens
authors.affiliation: U.S. Department of Energy (DOE), Office of River Protection , Richland, Washington 99352, United States.
authors.forename: Albert A
authors.initials: AA
authors.lastname: Kruger
authors.affiliation: Department of Chemistry, Washington State University , Pullman, Washington 99164, United States.
authors.forename: Nathalie A
authors.initials: NA
authors.lastname: Wall
authors.affiliation: Department of Chemistry, Washington State University , Pullman, Washington 99164, United States.|Pacific Northwest National Laboratory , Richland, Washington 99352, United States.|Materials Science and Engineering Program and School of Mechanical & Materials Engineering, Washington State University , Pullman, Washington 99164, United States.
authors.forename: John S
authors.identifier: http://orcid.org/0000-0001-7476-7771
authors.initials: JS
authors.lastname: McCloy