Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)

Abstract Compounds with the formulae CaZr1−xCexTi2O7 with x = 0.1–0.5 were synthesized by solid state reaction. Cerium was used as a surrogate for actinide elements. A transition from the 2M polymorph to the 4M polymorph (expanded unit cell due to cation ordering) in zirconolite was observed with in...

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Autores principales:	Braeden M. Clark, S. K. Sundaram, Scott T. Misture
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2017
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/e94f2ffcbff0465eb9567d40da2da947
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spelling	oai:doaj.org-article:e94f2ffcbff0465eb9567d40da2da9472021-12-02T16:07:57ZPolymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)10.1038/s41598-017-06407-52045-2322https://doaj.org/article/e94f2ffcbff0465eb9567d40da2da9472017-07-01T00:00:00Zhttps://doi.org/10.1038/s41598-017-06407-5https://doaj.org/toc/2045-2322Abstract Compounds with the formulae CaZr1−xCexTi2O7 with x = 0.1–0.5 were synthesized by solid state reaction. Cerium was used as a surrogate for actinide elements. A transition from the 2M polymorph to the 4M polymorph (expanded unit cell due to cation ordering) in zirconolite was observed with increasing cerium content. The presence of both tri- and tetravalent Ce, contrary to formulation, was confirmed using X-ray absorption near edge spectroscopy, suggesting substitution on both Ca and Zr sites. Sintering was carried out via spark plasma sintering, during which the perovskite phase (Ca0.4Ce0.4TiO3) was stabilized due to the reducing conditions of this technique. Scanning electron microscopy and energy dispersive spectrometry revealed that the 2M polymorph was dilute in Ce content in comparison to the 4M-zirconolite. High temperature X-ray diffraction was used to detail the kinetics of perovskite to zirconolite transition. It was found that CaCeTi2O7 (cubic pyrochlore) formed as an intermediate phase during the transition. Our results show that a transition from 2M- to 4M-zirconolite occurs with increasing Ce content and can be controlled by adjusting the PO2 and the heat treatment temperature.Braeden M. ClarkS. K. SundaramScott T. MistureNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 7, Iss 1, Pp 1-9 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Braeden M. Clark S. K. Sundaram Scott T. Misture Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)
description	Abstract Compounds with the formulae CaZr1−xCexTi2O7 with x = 0.1–0.5 were synthesized by solid state reaction. Cerium was used as a surrogate for actinide elements. A transition from the 2M polymorph to the 4M polymorph (expanded unit cell due to cation ordering) in zirconolite was observed with increasing cerium content. The presence of both tri- and tetravalent Ce, contrary to formulation, was confirmed using X-ray absorption near edge spectroscopy, suggesting substitution on both Ca and Zr sites. Sintering was carried out via spark plasma sintering, during which the perovskite phase (Ca0.4Ce0.4TiO3) was stabilized due to the reducing conditions of this technique. Scanning electron microscopy and energy dispersive spectrometry revealed that the 2M polymorph was dilute in Ce content in comparison to the 4M-zirconolite. High temperature X-ray diffraction was used to detail the kinetics of perovskite to zirconolite transition. It was found that CaCeTi2O7 (cubic pyrochlore) formed as an intermediate phase during the transition. Our results show that a transition from 2M- to 4M-zirconolite occurs with increasing Ce content and can be controlled by adjusting the PO2 and the heat treatment temperature.
format	article
author	Braeden M. Clark S. K. Sundaram Scott T. Misture
author_facet	Braeden M. Clark S. K. Sundaram Scott T. Misture
author_sort	Braeden M. Clark
title	Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)
title_short	Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)
title_full	Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)
title_fullStr	Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)
title_full_unstemmed	Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)
title_sort	polymorphic transitions in cerium-substituted zirconolite (cazrti2o7)
publisher	Nature Portfolio
publishDate	2017
url	https://doaj.org/article/e94f2ffcbff0465eb9567d40da2da947
work_keys_str_mv	AT braedenmclark polymorphictransitionsinceriumsubstitutedzirconolitecazrti2o7 AT sksundaram polymorphictransitionsinceriumsubstitutedzirconolitecazrti2o7 AT scotttmisture polymorphictransitionsinceriumsubstitutedzirconolitecazrti2o7
_version_	1718384689888100352

Polymorphic Transitions in Cerium-Substituted Zirconolite (CaZrTi2O7)

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