Zirconium incorporation into CaTiO3 perovskite prepared from xerogels and implication for the fate of (Ca, Sr) TiO3 nuclear waste ceramics

Nissim U. Navi; Giora Kimmel; Guy Yardeni; Jacob Zabicky; Roni Z. Shneck; Moshe H. Mintz; Alexandra Navrotsky

doi:10.1111/jace.12377

Zirconium incorporation into CaTiO₃ perovskite prepared from xerogels and implication for the fate of (Ca, Sr) TiO₃ nuclear waste ceramics

Nissim U. Navi, Giora Kimmel, Guy Yardeni, Jacob Zabicky, Roni Z. Shneck, Moshe H. Mintz, Alexandra Navrotsky

Research output: Contribution to journal › Article › peer-review

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Abstract

CaTiO₃ perovskite has been proposed as a ceramic waste form for immobilization of ⁹⁰Sr. Nonradioactive coprecipitated xerogel powders with nominal atomic ratios of Ca:Zr:Ti = 0.75:0.25:1.00 were synthesized to mimic the fate of (Ca_0.75⁹⁰Sr_0.25)TiO ₃ solid solution after complete decay of the Sr and its intermediate product Y to stable Zr when an excess B⁴⁺ (Ti and ⁹⁰Zr) cations will present. Ca:Ti = 1.00:1.00 samples were used as a reference. The powders were heated to various conditions to explore the thermodynamic stability of its oxides. The heated Ca:Zr:Ti = 0.75:0.25:1.00 samples formed a major orthorhombic Ca(Zr_1-xTi_x)O₃ perovskite phase. The Ti/(Ti + Zr) ratio of the perovskite preserves its nominal ratio at 600°C. The Zr rejects from the Ca(Zr_1-xTi_x)O ₃ with further increasing the temperature, following the formation of Ca-Ti-Zr-O secondary phases. This study indicates a tendency of the Zr to segregate from an original (Ca,Sr)TiO₃ waste form when the stoichiometry is controlled by the conversion of Sr to Zr (in normal oxidation states).

Original language	English
Pages (from-to)	2644-2650
Number of pages	7
Journal	Journal of the American Ceramic Society
Volume	96
Issue number	8
DOIs	https://doi.org/10.1111/jace.12377
State	Published - 1 Aug 2013

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Ceramics and Composites
Materials Chemistry

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title = "Zirconium incorporation into CaTiO3 perovskite prepared from xerogels and implication for the fate of (Ca, Sr) TiO3 nuclear waste ceramics",

abstract = "CaTiO3 perovskite has been proposed as a ceramic waste form for immobilization of 90Sr. Nonradioactive coprecipitated xerogel powders with nominal atomic ratios of Ca:Zr:Ti = 0.75:0.25:1.00 were synthesized to mimic the fate of (Ca0.7590Sr0.25)TiO 3 solid solution after complete decay of the Sr and its intermediate product Y to stable Zr when an excess B4+ (Ti and 90Zr) cations will present. Ca:Ti = 1.00:1.00 samples were used as a reference. The powders were heated to various conditions to explore the thermodynamic stability of its oxides. The heated Ca:Zr:Ti = 0.75:0.25:1.00 samples formed a major orthorhombic Ca(Zr1-xTix)O3 perovskite phase. The Ti/(Ti + Zr) ratio of the perovskite preserves its nominal ratio at 600°C. The Zr rejects from the Ca(Zr1-xTix)O 3 with further increasing the temperature, following the formation of Ca-Ti-Zr-O secondary phases. This study indicates a tendency of the Zr to segregate from an original (Ca,Sr)TiO3 waste form when the stoichiometry is controlled by the conversion of Sr to Zr (in normal oxidation states).",

author = "Navi, {Nissim U.} and Giora Kimmel and Guy Yardeni and Jacob Zabicky and Shneck, {Roni Z.} and Mintz, {Moshe H.} and Alexandra Navrotsky",

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AU - Navi, Nissim U.

AU - Kimmel, Giora

AU - Yardeni, Guy

AU - Zabicky, Jacob

AU - Shneck, Roni Z.

AU - Mintz, Moshe H.

AU - Navrotsky, Alexandra

PY - 2013/8/1

Y1 - 2013/8/1

N2 - CaTiO3 perovskite has been proposed as a ceramic waste form for immobilization of 90Sr. Nonradioactive coprecipitated xerogel powders with nominal atomic ratios of Ca:Zr:Ti = 0.75:0.25:1.00 were synthesized to mimic the fate of (Ca0.7590Sr0.25)TiO 3 solid solution after complete decay of the Sr and its intermediate product Y to stable Zr when an excess B4+ (Ti and 90Zr) cations will present. Ca:Ti = 1.00:1.00 samples were used as a reference. The powders were heated to various conditions to explore the thermodynamic stability of its oxides. The heated Ca:Zr:Ti = 0.75:0.25:1.00 samples formed a major orthorhombic Ca(Zr1-xTix)O3 perovskite phase. The Ti/(Ti + Zr) ratio of the perovskite preserves its nominal ratio at 600°C. The Zr rejects from the Ca(Zr1-xTix)O 3 with further increasing the temperature, following the formation of Ca-Ti-Zr-O secondary phases. This study indicates a tendency of the Zr to segregate from an original (Ca,Sr)TiO3 waste form when the stoichiometry is controlled by the conversion of Sr to Zr (in normal oxidation states).

AB - CaTiO3 perovskite has been proposed as a ceramic waste form for immobilization of 90Sr. Nonradioactive coprecipitated xerogel powders with nominal atomic ratios of Ca:Zr:Ti = 0.75:0.25:1.00 were synthesized to mimic the fate of (Ca0.7590Sr0.25)TiO 3 solid solution after complete decay of the Sr and its intermediate product Y to stable Zr when an excess B4+ (Ti and 90Zr) cations will present. Ca:Ti = 1.00:1.00 samples were used as a reference. The powders were heated to various conditions to explore the thermodynamic stability of its oxides. The heated Ca:Zr:Ti = 0.75:0.25:1.00 samples formed a major orthorhombic Ca(Zr1-xTix)O3 perovskite phase. The Ti/(Ti + Zr) ratio of the perovskite preserves its nominal ratio at 600°C. The Zr rejects from the Ca(Zr1-xTix)O 3 with further increasing the temperature, following the formation of Ca-Ti-Zr-O secondary phases. This study indicates a tendency of the Zr to segregate from an original (Ca,Sr)TiO3 waste form when the stoichiometry is controlled by the conversion of Sr to Zr (in normal oxidation states).

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Zirconium incorporation into CaTiO₃ perovskite prepared from xerogels and implication for the fate of (Ca, Sr) TiO₃ nuclear waste ceramics

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