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Article: Synergistic Effects of Ln and Fe Co-Doping on Phase Evolution of Ca1-xLnxZrTi2-xFexO7 (Ln = La, Nd, Gd, Ho, Yb) Ceramics
Title | Synergistic Effects of Ln and Fe Co-Doping on Phase Evolution of Ca1-xLnxZrTi2-xFexO7 (Ln = La, Nd, Gd, Ho, Yb) Ceramics |
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Authors | |
Keywords | Nuclear wastex Phase transformations Solid solutions Zirconolite |
Issue Date | 2018 |
Publisher | Elsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/jnucmat |
Citation | Journal of Nuclear Materials, 2018, v. 511, p. 428-437 How to Cite? |
Abstract | Zirconolite (CaZrTi2O7) is one of the host ceramic waste forms for actinides immobilization. In this study, lanthanides were used as the surrogates for actinides and a series of solid solutions (Ca(1-x)Ln(x)ZrTi(2-x)Fe(x)O(7): Ln = La, Nd, Gd, Ho, Yb) have been successfully fabricated to investigate the synergistic effects of Ln and Fe co-doping on phase evolution and solubility of Ln in zirconolite. Results show that zirconolite was found to co-exist with perovskite in the range 0.1 <= x <= 0.7 while zirconia, pseudobrookite, and perovskite become the major crystalline phases at 0.8 <= x <= 1.0 in the Ca1-xLaxZrTi2-xFexO7 ceramics. Both of zirconolite-2M and Zirconolite-3O were found in the Ca1-xNdxZrTi2-xFexO7 and Ca1-xGdxZrTi2-xFexO7 solid solutions. The phase transformation of zirconolite-2M to 3O occurs at x = 0.6 for Ca1-xNdxZrTi2-xFexO7 when this phenomenon happens at x = 0.9 for Ca1-xGdxZrTi2-xFexO7. The solubility of Ca1-xHoxZrTi2-xFexO7 to form single zirconolite-2M structure can be up to 0.9. Single zirconolite-2M was only detected within 0.1 <= x <= 0.6 in the Ca1-xYbxZrTi2-xFexO7 solid solutions. Lattice parameters of zirconolite-2M and zirconolite-3O were determined by Fawley refinement method. The lattice parameters of both zirconolite 2M and 3O gradually increase with increasing Nd and Fe contents in the Ca1-xNdxZrTi2-xFexO7 ceramics. For Ca1-xGdxZrTi2-xFexO7, the lattice parameter a has an increase with x increasing while b and c change slightly. For the Ho-Fe co-doped zirconolite-2M, the lattice parameter a shows an increasing trend, b and c demonstrate reverse trend when increasing Ho and Fe concentrations. Both b and c decrease with x increasing from 0.1 to 0.6 in the Ca1-xYbxZrTi2-xFexO7 while a has a slight change. The variation trends in the lattice parameters of zirconolite-2M phase in Ca1-xREExZrTi2-xFexO7 (REE = Nd, Gd, Ho, Yb) solid solutions are different, and such results may suggest different substitution mechanisms of lanthanide ions and Fe3+ in zirconolite. (C) 2018 Elsevier B.V. All rights reserved. |
Persistent Identifier | http://hdl.handle.net/10722/274865 |
ISSN | 2023 Impact Factor: 2.8 2023 SCImago Journal Rankings: 0.923 |
ISI Accession Number ID |
DC Field | Value | Language |
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dc.contributor.author | Ji, S | - |
dc.contributor.author | Li, Y | - |
dc.contributor.author | Ma, S | - |
dc.contributor.author | Liu, C | - |
dc.contributor.author | Shih, K | - |
dc.contributor.author | Liao, C | - |
dc.date.accessioned | 2019-09-10T02:30:29Z | - |
dc.date.available | 2019-09-10T02:30:29Z | - |
dc.date.issued | 2018 | - |
dc.identifier.citation | Journal of Nuclear Materials, 2018, v. 511, p. 428-437 | - |
dc.identifier.issn | 0022-3115 | - |
dc.identifier.uri | http://hdl.handle.net/10722/274865 | - |
dc.description.abstract | Zirconolite (CaZrTi2O7) is one of the host ceramic waste forms for actinides immobilization. In this study, lanthanides were used as the surrogates for actinides and a series of solid solutions (Ca(1-x)Ln(x)ZrTi(2-x)Fe(x)O(7): Ln = La, Nd, Gd, Ho, Yb) have been successfully fabricated to investigate the synergistic effects of Ln and Fe co-doping on phase evolution and solubility of Ln in zirconolite. Results show that zirconolite was found to co-exist with perovskite in the range 0.1 <= x <= 0.7 while zirconia, pseudobrookite, and perovskite become the major crystalline phases at 0.8 <= x <= 1.0 in the Ca1-xLaxZrTi2-xFexO7 ceramics. Both of zirconolite-2M and Zirconolite-3O were found in the Ca1-xNdxZrTi2-xFexO7 and Ca1-xGdxZrTi2-xFexO7 solid solutions. The phase transformation of zirconolite-2M to 3O occurs at x = 0.6 for Ca1-xNdxZrTi2-xFexO7 when this phenomenon happens at x = 0.9 for Ca1-xGdxZrTi2-xFexO7. The solubility of Ca1-xHoxZrTi2-xFexO7 to form single zirconolite-2M structure can be up to 0.9. Single zirconolite-2M was only detected within 0.1 <= x <= 0.6 in the Ca1-xYbxZrTi2-xFexO7 solid solutions. Lattice parameters of zirconolite-2M and zirconolite-3O were determined by Fawley refinement method. The lattice parameters of both zirconolite 2M and 3O gradually increase with increasing Nd and Fe contents in the Ca1-xNdxZrTi2-xFexO7 ceramics. For Ca1-xGdxZrTi2-xFexO7, the lattice parameter a has an increase with x increasing while b and c change slightly. For the Ho-Fe co-doped zirconolite-2M, the lattice parameter a shows an increasing trend, b and c demonstrate reverse trend when increasing Ho and Fe concentrations. Both b and c decrease with x increasing from 0.1 to 0.6 in the Ca1-xYbxZrTi2-xFexO7 while a has a slight change. The variation trends in the lattice parameters of zirconolite-2M phase in Ca1-xREExZrTi2-xFexO7 (REE = Nd, Gd, Ho, Yb) solid solutions are different, and such results may suggest different substitution mechanisms of lanthanide ions and Fe3+ in zirconolite. (C) 2018 Elsevier B.V. All rights reserved. | - |
dc.language | eng | - |
dc.publisher | Elsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/jnucmat | - |
dc.relation.ispartof | Journal of Nuclear Materials | - |
dc.subject | Nuclear wastex | - |
dc.subject | Phase transformations | - |
dc.subject | Solid solutions | - |
dc.subject | Zirconolite | - |
dc.title | Synergistic Effects of Ln and Fe Co-Doping on Phase Evolution of Ca1-xLnxZrTi2-xFexO7 (Ln = La, Nd, Gd, Ho, Yb) Ceramics | - |
dc.type | Article | - |
dc.identifier.email | Shih, K: kshih@hku.hk | - |
dc.identifier.email | Liao, C: liaocz@HKUCC-COM.hku.hk | - |
dc.identifier.authority | Shih, K=rp00167 | - |
dc.description.nature | link_to_subscribed_fulltext | - |
dc.identifier.doi | 10.1016/j.jnucmat.2018.09.043 | - |
dc.identifier.scopus | eid_2-s2.0-85054020483 | - |
dc.identifier.hkuros | 303527 | - |
dc.identifier.volume | 511 | - |
dc.identifier.spage | 428 | - |
dc.identifier.epage | 437 | - |
dc.identifier.isi | WOS:000447796300043 | - |
dc.publisher.place | Netherlands | - |
dc.identifier.issnl | 0022-3115 | - |