Could the Oxygen Vacancy in Oxides of the Perovskite Family Be a Dipole Center?

Prosandeyev, S. A.; Osipenko, I. A.

doi:10.1002/pssb.2221920105

Cited by 18 publications

(14 citation statements)

References 11 publications

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“…Later on, theoretical studies performed in the framework of a Green function approach considered possible reasons for such symmetry breaking. 3,4 Within that study the electron's activation energies were obtained in accordance with data on electroconductivity 5 which we will discuss below.…”

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confidence: 59%

“…Theoretical studies 3,4 did not consider the states of the F -center-type (a vacancy centered, symmetric electron density), but, later, computations showed that the states of the F -center type , in the single charged oxygen vacancy (V + O ), can have lower energy than the states of the V ++ O Ti 3+ -type 6,7,8 . However, the EPR signal of such states has not been found experimentally.…”

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confidence: 99%

“…In semiempirical theoretical studies 3,4,5 it was obtained that the symmetry broken electronic state V ++ O T i 3+ has the energy about 0.2 eV with respect to the conduction band bottom plus the polaronic energy connected with the interaction of the microscopic dipole with lattice polarization. This is in very good agreement with the data on electroconductivity.…”

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Comment on “Conduction states in oxide perovskites: Three manifestations ofTi3+Jahn-Teller polarons in barium titanate”

2004

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In this comment to S. Lenjer, O. F. Schirmer, H. Hesse, and Th. W. Kool, Phys. Rev. B 66, 165106 (2002), we discuss the electronic structure of oxygen vacancies in perovskites. First-principles computations are in favor of rather deep levels in these vacancies, and Lenjer et al. even suggest that the electrons' interaction energy is negative. However, data on electroconductivity are against both these scenarios.It has been well established by gravimetric measurements that the thermal annealing of BaTiO 3 results in reversible changes of the oxygen content. 1,2 Computations in the framework of the shell model 3,4 as well as the quasichemical reactions approach (based on the dependence of conductivity on oxygen partial pressure 5-7 ) showed that, after annealing at 1000 K Ͼ T Ͼ 500 K, the main defects are of Shottky type, and the appearance of oxygen vacancies ͑V O ͒ is much more probable than the vacancies on other sites. This has been confirmed, for instance, by experiments on electroconductivity (see Ref. 8 and references therein) and oxygen diffusion (with isotopes). 9 The increase of the V O concentration increases n-type conductivity. At a large V O concentration, their ordering by the formation of shear planes can take place. 10 Reduction of the samples changes the color from transparent light-yellow to blue, and, at large concentration, to black. There appears characteristic absorbtion of light. 11 Doping the samples with p-type impurities is compensated by the appearance of V O at annealing.Annealing in the oxygen atmosphere decreases n-type conductivity and p-type conductivity can appear at a large exposure time. This is usually interpreted as the presence in the samples (even single crystals) of unavoidable p-type impurities. Depending on the degree of the compensation of V O and p-type impurities, V O can accept two electrons (neutral vacancy), single charged V O + has one electron, and, finally, V O ++ without electrons is double charged. Also, V O + and V O can have a high degree of compensation (hdc) (the Fermi level coincides with the energy level position) or low degree of compensation (ldc) (the Fermi level is at the middle between the energy level and the conduction band bottom. Thus, the oxygen vacancy is a multiple-charge center and, in order to treat the thermodynamics of electrons on such centers one has to consider the grand canonical ensemble. 8 Electroconductivity data show that all these states can be observed if one varies the degree of the defects' compensation 8 (see Table I). Note that these energies were observed in samples having different values of conductivity: very high for V O and much smaller for V O + . These samples had different color: black or gray (very small activation energies inherent to V O ) or light-yellow (comparatively deep levels corresponding to V O + ). By using electron paramagnetic resonance (EPR) spectroscopy, Scharfschwerdt et al. 12 found a signal in reduced BaTiO 3 which they attributed to a symmetry broken state of Ti 3+ bound to V O ++ ͑V O ++ Ti 3+ ͒. S...

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Comment on “Conduction states in oxide perovskites: Three manifestations ofTi3+Jahn-Teller polarons in barium titanate”

2004

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“…All these studies were performed on the assumption that the symmetry of V O coincides with the point symmetry of the oxygen site in the ideal crystal. However, recently, it was shown that the single-charged V + O may be a dipole centre [12][13][14][15]. In this case, an electron captured by V O predominantly localizes on one of the neighbours to the V O ions.…”

Section: Introductionmentioning

confidence: 99%

Study of intrinsic point defects in oxides of the perovskite family: I. Theory

Prosandeyev

Fisenko

Riabchinski

et al. 1996

J. Phys.: Condens. Matter

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Special features of atomic vacancies in oxides of the perovskite family have been studied within the framework of the Green function method. It has been shown that, in accordance with experiments, the oxygen vacancy has both shallow and comparatively deep levels corresponding to different charge states. The single-charged oxygen vacancy has a deep level and, hence, it could be a good trap for electrons. We shall show that, owing to interaction with the lattice polarization, an electron is captured by one of the neighbours to the vacancy ions. As a result the single-charged oxygen vacancy proves to be a dipole centre. Peculiarities in the optical absorption spectra connected with the single-charged oxygen vacancy are discussed.

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“…The observation of the Fano effect, and the suggestions based on it that local polar regions exist in STO thin films, may hold the key to the understanding of the lattice dynamical and dielectric properties of ferroelectric thin films. The existence of such local polar regions around defects or oxygen vacancies has been proposed in bulk materials both experimentally [27,28,44,56] and theoretically [57][58][59].…”

Section: Discussionmentioning

confidence: 97%

Lattice dynamical properties of SrTiO[sub 3] thin films

Sirenko¹,

Акимов²,

Bernhard³

et al. 2000

AIP Conference Proceedings

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We report the experimental studies of the vibrational spectra of SrTiO 3 films grown by pulsed laser deposition. Raman scattering, with and without bias electric field, and Fourier-transform far-infrared ellipsometry between 30 and 700 cm −1 have been utilized for investigation of the phonon behavior. These results are discussed in connection with the low-frequency dielectric properties of the SrTiO 3 films. In the films, the soft mode reveals hardening compared to that in bulk crystals. This observation is in agreement with the Lyddane-Sachs-Teller formalism. The existence of local polar regions is proposed as an important factor determining the dielectric properties of ferroelectric thin films.

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Could the Oxygen Vacancy in Oxides of the Perovskite Family Be a Dipole Center?

Cited by 18 publications

References 11 publications

Comment on “Conduction states in oxide perovskites: Three manifestations ofTi3+Jahn-Teller polarons in barium titanate”

Comment on “Conduction states in oxide perovskites: Three manifestations ofTi3+Jahn-Teller polarons in barium titanate”

Study of intrinsic point defects in oxides of the perovskite family: I. Theory

Lattice dynamical properties of SrTiO[sub 3] thin films

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