Premium
Thermochemistry of ( Ca x Sr 1‐ x ) TiO 3 , ( Ba x Sr 1‐ x ) TiO 3 , and ( Ba x Ca 1‐x ) TiO 3 Perovskite Solid Solutions
Author(s) -
Navi Nissim U.,
Shneck Roni Z.,
Shvareva Tatiana Y.,
Kimmel Giora,
Zabicky Jacob,
Mintz Moshe H.,
Navrotsky Alexandra
Publication year - 2012
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.1551-2916.2012.05137.x
Subject(s) - ionic radius , phase diagram , solid solution , enthalpy , orthorhombic crystal system , tetragonal crystal system , calorimetry , analytical chemistry (journal) , crystallography , perovskite (structure) , materials science , mineralogy , chemistry , phase (matter) , thermodynamics , crystal structure , physics , ion , organic chemistry , chromatography , metallurgy
High‐temperature solution calorimetry in molten 3Na 2 O • 4MoO 3 solvent at 975 K is used to measure the enthalpy of mixing of ( Ca x Sr 1‐ x ) TiO 3 and ( Ba x Sr 1‐ x ) TiO 3 solid solutions. Both solid solutions show positive enthalpy of mixing, however, the ( Ba x Sr 1‐ x ) TiO 3 shows less deviation from ideality, with interaction parameter λ = 8.5 ± 3.8 kJ/mol, than ( Ca x Sr 1‐ x ) TiO 3 with interaction parameter λ = 25.3 ± 2.0 kJ/mol. The smaller interaction parameter of the ( Ba x Sr 1‐ x ) TiO 3 system is attributed to the volume mismatch of the end‐members. The larger interaction parameter of ( Ca x Sr 1‐ x ) TiO 3 may be related to larger ionic radius difference of Ca and Sr and may also reflect the additional energy needed to overcome the lattice distortion of the orthorhombic CaTiO 3 to incorporate it into the cubic perovskite SrTiO 3 . ( Ba x Ca 1‐ x ) TiO 3 has a large positive heat of mixing and limited solid solubility as derived from its phase diagram. This study indicates the tendency of SrTiO 3 and BaTiO 3 to separate from a CaTiO 3 host matrix, which may be significant in perovskite‐bearing nuclear waste ceramics incorporating 90 Sr and 137 Ba .