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Yttrium Substitution in MTiO 3 (M=Ca, Sr, Ba and Ca+Sr+Ba) Perovskites and Implication for Incorporation of Fission Products into Ceramic Waste Forms
Author(s) -
Navi Nissim U.,
Kimmel Giora,
Zabicky Jacob,
Ushakov Sergey V.,
Shneck Roni Z.,
Mintz Moshe H.,
Navrotsky Alexandra
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.04474.x
Subject(s) - pyrochlore , yttrium , perovskite (structure) , materials science , ceramic , fission products , phase (matter) , mineralogy , homogeneous , nuclear chemistry , crystallography , analytical chemistry (journal) , chemistry , metallurgy , radiochemistry , oxide , thermodynamics , organic chemistry , physics , chromatography
CaTiO 3 has been proposed as a ceramic waste form for immobilization of radioactive waste that might include short‐lived fission products 137 Cs and 90 Sr and consequently their decay products 137 Ba (stable), 90 Y (intermediate), and 90 Zr (stable). In order to characterize substitution relations of Y 3+ for M 2+ (M=Ca, Sr, Ba singly or in combination) in MTiO 3 , precursor mixtures with nominal atomic ratios of M:Y:Ti=0.75:0.25:1 were synthesized by solid‐state reactions. To ensure homogeneous starting material and to explore low temperature behavior of the Ca–Y–Ti–O system, coprecipitated xerogel powder was synthesized and heated to various temperatures for different periods of time. All M–Y–Ti–O systems formed two major phase mixtures of perovskite MTiO 3 and pyrochlore Y 2 Ti 2 O 7 with low substitution of M 2+ by Y 3+ in MTiO 3 and Y 3+ by M 2+ in Y 2 Ti 2 O 7 . The study of xerogel confirmed the tendency of the formation of mixtures of CaTiO 3 and Y 2 Ti 2 O 7 phases, even at lower temperature. The temperature dependence of the substitution of Ca 2+ by Y 3+ in CaTiO 3 appears to be small. Despite the minor substitution of M by Y in the perovskite no significant 90 Y 3+ build‐up is expected to occur in the waste form due to the rapid decay of 90 Y 3+ relative to that of 90 Sr 2+ .