TY - JOUR
T1 - Synthesis, charac terization and thermochemistry of Cs-, Rb- and Sr-substituted barium aluminium titanate hollandites
AU - Xu, H.
AU - Wu, L.
AU - Zhu, J.
AU - Navrotsky, A.
N1 - Funding Information:
This work was supported by the laboratory-directed research and development (LDRD) program of Los Alamos National Laboratory , which is operated by Los Alamos National Security LLC, under DOE Contract DE-AC52-06NA25396. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S. DOE, Office of Science, Office of Basic Energy Sciences , under Contract No. DE-AC02-06CH11357 .
Publisher Copyright:
© 2015 Elsevier B.V. All rights reserved.
PY - 2015/4
Y1 - 2015/4
N2 - Titanate hollandites are of considerable interest for immobilization of radioactive Cs, its daughter product Ba and related radionuclides Rb and Sr. In this study, 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. This trend is consistent with the phase assemblage observed in Synroc, where Cs+, Rb+ and Ba2+ enter into hollandite, whereas Sr2+ occurs in perovskite.
AB - Titanate hollandites are of considerable interest for immobilization of radioactive Cs, its daughter product Ba and related radionuclides Rb and Sr. In this study, 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. This trend is consistent with the phase assemblage observed in Synroc, where Cs+, Rb+ and Ba2+ enter into hollandite, whereas Sr2+ occurs in perovskite.
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U2 - 10.1016/j.jnucmat.2015.01.014
DO - 10.1016/j.jnucmat.2015.01.014
M3 - Article
AN - SCOPUS:84921290542
SN - 0022-3115
VL - 459
SP - 70
EP - 76
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
ER -