Similar local order in disordered fluorite and aperiodic pyrochlore structures

Predicting short-range order and correlated phenomena in disordered crystalline materials

“…While we have shown the examples of the behavior of spinel and pyrochlore structures, we have experimental data that show the same behavior for doped ThO 2 , A 2 BO 5 oxides, and A 3 BO 7 oxides. Furthermore, this complexity has been observed in materials disordered by nonstoichiometry ( 43 ), intense radiation ( 10 ), mechanochemical synthesis ( 44 ), or temperature exposure ( 45 ). This demonstrates that the new disordering concept presented in this study is, as Pauling’s rules were for ordered ionic compounds, a general phenomenon for a wide range of disordered materials independent on how the disorder is introduced.…”

Optimizing the Reaction Performance of La2Ce2O7‐Based Catalysts for Oxidative Coupling of Methane (OCM) at Lower Temperature by Lattice Doping with Ca Cations

“…For example, compared with the ordered cubic fluorite phase, the disordered defective cubic fluorite phase typically possesses an 8a intrinsic oxygen vacancy in a unit cell , , . As a consequence, the average oxygen coordination number (CN) of the total A and B metal cations in a disordered defective cubic fluorite phase is 7, which is less than CN = 8 in a perfect cubic fluorite phase . In addition, the A and B cations are distributed randomly in the sublattices, and the inherent oxygen vacancies are highly disordered, thus resulting in evident improvement of lattice oxygen mobility, and eventually generating abundant facile surface oxygen sites , , …”

Disorder in Ho2Ti2−xZrxO7: pyrochlore to defect fluorite solid solution series

“…48 Random averaging of weberite-type local congurations leads to a long-range disordered, defect uorite structure when averaged over many unit cells. 44,46 Heterogeneous disordering processes with different short-and longrange structural motifs have been similarly observed for other ceramics, such as spinel, 49 and different disordering processes through intrinsic (nonstoichiometry and chemical composition 15,50 ) and extrinsic (ball milling and irradiation 43,51 ) means. This behavior is consistent with Pauling's rules which have been shown to dictate the local atomic arrangements in disordered ceramics.…”

“…25,31,35,40,41 Recent studies using neutron total scattering experiments with pair distribution function (PDF) analysis of disordered pyrochlore (e.g., Ho 2 Zr 2 O 7 ) have uncovered that the local atomic arrangement of the defect uorite phase is actually described by a partially ordered orthorhombic phase, 42 the structure of which can be described by a weberite-type (C222 1 ) structural model that is isostructural to Y 3 TaO 7 . [42][43][44][45][46][47] The weberite-type structure is another derivative of the uorite structure with a 2  ffiffiffi 2 p  ffiffiffi 2 p superstructure that contains a higher degree of ordered arrangements of different valence cations and ordered anion vacancies as compared with defect uorite but is distinct from pyrochlore (Fig. 1c).…”