Synthesis, characterization and thermochemistry of Cs-, Rb- and Sr-substituted barium aluminium titanate hollandites
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Univ. of California, Davis, CA (United States)
Titanate hollandites are of considerable interest for immobilization of radioactive Cs, its daughter product Ba and related radionuclides Rb and Sr. In this work, we synthesized three hollandites, Ba1.18Cs0.21Al2.44Ti5.53O16, Ba1.17Rb0.19Al2.46Ti5.53O16 and Ba1.14Sr0.10Al2.38Ti5.59O16, using sol–gel methods. Rietveld analysis of synchrotron XRD data shows that they adopt the tetragonal structure (space group I4/m), and their cell parameters increase with increasing cation size (Sr2+ → Rb+ → Cs+). Standard enthalpies of formation of these hollandites were determined from drop solution calorimetric measurements with lead borate as the solvent at 973 K. Their formation enthalpies are similar, consistent with the occurrence of extensive cation substitutions in hollandites. Further energetic analysis with respect to BaTiO3 and SrTiO3 perovskites and other oxides reveals decreased thermodynamic stability from Cs- to Rb- to Sr-hollandite. Lastly, this trend is consistent with the phase assemblage observed in Synroc, where Cs+, Rb+ and Ba2+ enter into hollandite, whereas Sr2+ occurs in perovskite.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC52-06NA25396; AC02-06CH11357
- OSTI ID:
- 1471328
- Alternate ID(s):
- OSTI ID: 1246584
- Report Number(s):
- LA-UR-14-29122
- Journal Information:
- Journal of Nuclear Materials, Vol. 459, Issue C; ISSN 0022-3115
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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