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Title: Synthesis, characterization and thermochemistry of Cs-, Rb- and Sr-substituted barium aluminium titanate hollandites

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, Ba 1.18Cs 0.21Al 2.44Ti 5.53O 16, Ba 1.17Rb 0.19Al 2.46Ti 5.53O 16 and Ba 1.14Sr 0.10Al 2.38Ti 5.59O 16, 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 (Sr 2+ → 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 BaTiO 3 and SrTiO 3 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 Ba 2+ enter into hollandite, whereas Sr 2+ occurs in perovskite.
Authors:
ORCiD logo [1] ;  [2] ;  [1] ;  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of California, Davis, CA (United States)
Publication Date:
Report Number(s):
LA-UR-14-29122
Journal ID: ISSN 0022-3115
Grant/Contract Number:
AC52-06NA25396; AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 459; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; Hollandite; Crystal structure; Phase stability; Synchrotron X-ray diffraction; High-temperature oxide melt solution calorimetry
OSTI Identifier:
1471328
Alternate Identifier(s):
OSTI ID: 1246584

Xu, Hongwu, Wu, Lili, Zhu, Jinlong, and Navrotsky, Alexandra. Synthesis, characterization and thermochemistry of Cs-, Rb- and Sr-substituted barium aluminium titanate hollandites. United States: N. p., Web. doi:10.1016/j.jnucmat.2015.01.014.
Xu, Hongwu, Wu, Lili, Zhu, Jinlong, & Navrotsky, Alexandra. Synthesis, characterization and thermochemistry of Cs-, Rb- and Sr-substituted barium aluminium titanate hollandites. United States. doi:10.1016/j.jnucmat.2015.01.014.
Xu, Hongwu, Wu, Lili, Zhu, Jinlong, and Navrotsky, Alexandra. 2015. "Synthesis, characterization and thermochemistry of Cs-, Rb- and Sr-substituted barium aluminium titanate hollandites". United States. doi:10.1016/j.jnucmat.2015.01.014. https://www.osti.gov/servlets/purl/1471328.
@article{osti_1471328,
title = {Synthesis, characterization and thermochemistry of Cs-, Rb- and Sr-substituted barium aluminium titanate hollandites},
author = {Xu, Hongwu and Wu, Lili and Zhu, Jinlong and Navrotsky, Alexandra},
abstractNote = {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.},
doi = {10.1016/j.jnucmat.2015.01.014},
journal = {Journal of Nuclear Materials},
number = C,
volume = 459,
place = {United States},
year = {2015},
month = {1}
}