Disorder-induced optical and paramagnetic properties in zirconium dioxide: Role of low-symmetry crystal fields

Azzoni, C. B.; Bolis, L.; Палеари, А.; Samoggia, G.; Scardina, F.

doi:10.1103/physrevb.51.15942

Cited by 29 publications

(42 citation statements)

References 19 publications

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“…Therefore, the Zr 3+ O 2− bonds in YSZ may be mainly ionic. (ii) The displacement X (≈0.42Å) of the oxygen ligands towards the V O obtained in this work is also comparable with that (≈0.36Å) obtained from neutron diffraction measurements [30], and those (≈0.24-0.37Å) obtained from the optical spectral analysis and crystal-field calculations in the previous works [17,18]. Considering the strong electrostatic attraction between the oxygen ions in ligand triangles and the nearest V O , the large displacement X can be understood (see Fig.…”

Section: Discussionsupporting

confidence: 84%

“…So, the convergence of the formulas may be regarded as valid, under the condition of the strong cubic and trigonal crystal-fields in this work. (iii) Recent studies on the oscillator strength of optical transitions for the Zr 3+ center in YSZ revealed that local axial distortions without inversion symmetry account for the experimental optical absorption and EPR spectra [18]. The authors preferred C 3v to the strict D 3d symmetry i.e., the displacements of the oxygen ions in upper ( X 2 ≈ 0.37Å) and lower ligand triangles ( X 1 ≈ 0.24-0.37Å) may not be equivalent [16,18].…”

Section: Discussionmentioning

confidence: 99%

“…Later on, Azzoni et al [17,18] carried out the studies on the defect structure and crystal-field properties of trigonal six-foldcoordinated Zr 3+ center in YSZ, by proposing the displacements of about 0.24-0.37Å for the oxygen ligands towards the V O along the [1 0 0] directions. However, there seems to be some imperfectness in their investigations.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical investigations of the g factors and the local structure for the trigonal Zr3+ center in X-ray irradiated YSZ

Wu¹,

Dong²,

Zu³

2005

Journal of Alloys and Compounds

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Theoretical investigations of the g factors and the local structure for the trigonal Zr3+ center in X-ray irradiated YSZ

Wu¹,

Dong²,

Zu³

2005

Journal of Alloys and Compounds

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“…In addition the electron paramagnetic resonance (EPR) spectrum of YSZ contains a prominent trigonal (T centre) peak in samples that have been chemically reduced or exposed to ionizing radiation [28][29][30][31] . This peak has been assigned to a vacancy-vacancy pair lying in a ⟨1 1 1⟩ direction neighbouring a Ti 3+ impurity 27,32,33 .…”

Section: Introductionmentioning

confidence: 99%

Chemical Descriptors of Yttria-Stabilized Zirconia at Low Defect Concentration: An ab Initio Study

et al. 2015

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Keywords: solid oxide fuel cell, yttria stabilised zirconia, cubic zirconia, bixbyite yttria, ab initio, density functional theory, empirical potential, Born-Mayer-Huggins, point charge model, phonons, harmonic approximation. been observed in either X-ray or neutron diffraction experiments. The prediction of local defect structure and the interaction between defects is therefore of great interest. This has not been possible to date as the number of possible defect topologies is very large and to perform reliable total energy calculations for all of them would be prohibitively expensive. Previous theoretical studies have only considered a selection of representative structures. In this study, a comprehensive search for low energy defect structures using a combined classical modelling and density functional theory approach is used to identify the low energy isolated defect structures at the dilute limit, 3.2mol%. Through analysis of energetics computed using the best available Born-Mayer-Huggins empirical potential model, a point charge model, DFT, and a local strain energy estimated in the harmonic approximation, the main chemical and physical descriptors that correlate to the low energy DFT structures are discussed. It is found that the empirical potential model reproduces a general trend of increasing DFT energetics across a series of locally strain relaxed structures, but is unreliable both in predicting some incorrect low energy structures, and 3 in finding some meta-stable structures to be unstable. A better predictor of low energy defect structures is found to be the total electrostatic energy of a simple point charge model calculated at the unrelaxed geometries of the defects. In addition, the strain relaxation energy is estimated effectively in the harmonic approximation to the imaginary phonon modes of undoped c-ZrO 2 , but is found to be unimportant in determining the low energy defect structures. These results allow us to propose a set of easily computed descriptors that can be used to identify the low energy YSZ defect structures, negating the combinatorial complexity and number of defect structures that need to be considered. Abstract

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“…The low contrast in the X-ray and neutron scattering powers of Zr 4+ and Y 3+ ions has made it extremely difficult to deduce the relative positions of the Y 3+ and O vac species, or to determine the local geometry of the dopant structures 18 . On the basis of X-ray absorption fine structure spectroscopy (EXAFS) [28][29][30] [40][41][42][43] . This peak has been interpreted as a vacancy-vacancy pair lying in a ⟨1 1 1⟩ direction neighbouring a Ti 3+ impurity [44][45][46] .…”

Section: Introductionmentioning

confidence: 99%

The atomistic structure of yttria stabilised zirconia at 6.7 mol%: an ab initio study

Parkes

Tompsett

d’Avezac

et al. 2016

Phys. Chem. Chem. Phys.

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Keywords: solid oxide fuel cell, yttria stabilised zirconia, ab initio, density functional theory, empirical potential, Born-Mayer-Huggins, ReaxFF, point charge model. AbstractYttria stabilized zirconia (YSZ) is an important oxide ion conductor used in solid oxide fuel cells, oxygen sensing devices, and for oxygen separation. Doping pure zirconia (ZrO 2 ) with yttria (Y 2 O 3 ) stabilizes the cubic structure against phonon induced distortions and this facilitates high oxide ion conductivity. The local atomic structure of the dopant is, however, not fully understood. X-ray and neutron diffraction experiments have established that, for dopant concentrations below 40mol% Y 2 O 3 , no long range order is established. A variety of local structures have been suggested on the basis of theoretical and computational models of dopant energetics. These studies have been restricted by the difficulty of establishing force field models with predictive accuracy or exploring the large space of dopant configurations with first principles theory. In the current study a comprehensive search for all symmetry independent configurations (2857 candidates) is performed for 6.7mol% YSZ modelled in a 2x2x2 periodic supercell using gradient corrected density functional theory. The lowest energy dopant structures are found to have oxygen vacancy pairs preferentially aligned along the ⟨2 1 0⟩ crystallographic direction in contrast to previous results which have suggested that orientation along the ⟨1 1 1⟩ orientation is favourable. Analysis of the defect structures suggests that the Y 3+ -O vac interatomic separation is an important parameter for determining the relative configurational energies.Current force field models are found to be poor predictors of the lowest energy structures. It is suggested that the energies from a simple point charge model evaluated at unrelaxed geometries 3 is actually a better descriptor of the energy ordering of dopant structures. Using these observations a pragmatic procedure for identifying low energy structures in more complicated material models is suggested. Calculation of the oxygen vacancy migration activation energies within the lowest energy ⟨2 1 0⟩ oriented structures gives results consistent with experimental observations.

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Disorder-induced optical and paramagnetic properties in zirconium dioxide: Role of low-symmetry crystal fields

Cited by 29 publications

References 19 publications

Theoretical investigations of the g factors and the local structure for the trigonal Zr3+ center in X-ray irradiated YSZ

Theoretical investigations of the g factors and the local structure for the trigonal Zr3+ center in X-ray irradiated YSZ

Chemical Descriptors of Yttria-Stabilized Zirconia at Low Defect Concentration: An ab Initio Study

The atomistic structure of yttria stabilised zirconia at 6.7 mol%: an ab initio study

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