Defining the Structural Stability Field of Disordered Fluorite Oxides

Abstract

Fluorite-structured oxides constitute an important class of materials for energy technologies. Despite their high level of structural symmetry and simplicity, these materials can accommodate atomic disorder without losing crystallinity, making them indispensable for uses in environments with high temperature, changing chemical compositions, or intense radiation fields. In this contribution, we present a set of simple rules that predict whether a compound may adopt a disordered fluorite structure. This approach is closely aligned with Pauling’s rules for ionic crystal structures and Goldschmidt’s rules for ionic substitution.

Low-temperature properties of magnetically frustrated rare-earth zirconates A 2Zr2O7

“…Several A 2 B 2 O 7 members were found to crystallise in lower-symmetry structures: monoclinic [22], orthorhombic [23], and very recently Lu 2 Zr 2 O 7 was reported to adopt a rhombohedral structure (space group R-3) [24]. Moreover, there is an intense discussion about the local crystal structure in these materials diverging significantly from their average structure due to shortrange correlations [25][26][27][28][29]. That is, a strict classification of the respective average crystal structures can be misleading, as the underlying local correlations play a crucial role in interpreting the complex magnetic behaviour reported in these compounds.…”

Emerging disorder in Gd2(Ti1−xZrx)2O7 pyrochlores matrices for radioactive waste disposal: symmetry lowering versus defect clustering

“…[15][16][17][18] The ratio of the A and B ionic radii r A /r B has been extensively used to predict and explain the formation of different structural type as a function of ionic substitutions. 19,20 At atmospheric pressure, a pyrochlore phase is stable if the r A /r B is in the range 1.46-1.78, 10,21 whereas an anion decient uorite (A 0.5 B 0.5 )O 1.75 phase appears if r A /r B < 1.46. For r A /r B values exceeding 1.78, a monoclinic perovskite layered structure is favored.…”