Hopping and clustering of oxygen vacancies in BaTiO3− and the influence of the off-centred Ti atoms

Cordero, F.; Trequattrini, F.; Quiroga, David Antonio Barbosa; Silva, P.S.

doi:10.1016/j.jallcom.2021.159753

Cited by 14 publications

(3 citation statements)

References 65 publications

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“…Indeed, classical molecular‐dynamics simulations that employ the empirical pair‐potentials of Pedone et al. [ 52 ] have been shown [ 44,49 ] to reproduce experimental diffusion rates of oxygen vacancies in SrTiO 3 [ 19,27,53–55 ] and BaTiO 3 [ 38,56,57 ] extraordinarily well, not only in terms of the activation enthalpy of oxygen‐vacancy migration but also the absolute rate of vacancy diffusion. Here, we used molecular‐dynamics simulations with the empirical pair‐potentials of Pedone et al.…”

Section: Resultsmentioning

confidence: 99%

“…Moleculardynamics simulations constitute an optimal method [44,[49][50][51] for obtaining D v (T). Indeed, classical molecular-dynamics simulations that employ the empirical pair-potentials of Pedone et al [52] have been shown [44,49] to reproduce experimental diffusion rates of oxygen vacancies in SrTiO 3 [19,27,[53][54][55] and BaTiO 3 [38,56,57] extraordinarily well, not only in terms of the activation enthalpy of oxygen-vacancy migration but also the absolute rate of vacancy diffusion. Here, we used molecular-dynamics simulations with the empirical pair-potentials of Pedone et al [52] to calculate D v (T) in BaSnO 3 for four different cases: All simulation cells contained a fixed number of oxygen vacancies (40 distributed randomly over 8232 oxygen-ion sites) and either a background charge or the appropriate number (to compensate the oxygen vacancies' charge) of barium vacancies, barium antisites, or tin vacancies.…”

Section: Computational Investigationsmentioning

confidence: 99%

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Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO₃ Thin Films

Belthle

Gries

Mueller

et al. 2022

Adv Funct Materials

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The high-mobility, wide-bandgap perovskite oxide BaSnO 3 is taken as a model system to demonstrate that the native point defects present in un-doped, epitaxial thin films grown by hybrid molecular beam epitaxy can be identified and their concentrations at the ppm level determined quantitatively. An elevatedtemperature, multi-faceted approach is shown to be necessary: oxygen tracer diffusion experiments with secondary ion mass spectrometry analysis; molecular dynamics simulations of oxygen-vacancy diffusion; electronic conductivity studies as a function of oxygen activity and temperature; and Hall-effect measurements. The results indicate that the oxygen-vacancy concentration cannot be lowered below 10 17.3 cm −3 because of a background level of barium vacancies (of this concentration), introduced during film growth. The multi-faceted approach also yields the electron mobility over a wide temperature range, coefficients of oxygen surface exchange and oxygen-vacancy diffusion, and the reduction enthalpy. The consequences of the results for the lowest electron concentration achievable in BaSnO 3 samples, for the ease of oxide reduction and for the stability of reduced films with respect to oxidation, are discussed.

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Section: Resultsmentioning

confidence: 99%

Section: Computational Investigationsmentioning

confidence: 99%

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO₃ Thin Films

Belthle

Gries

Mueller

et al. 2022

Adv Funct Materials

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“…The charge compensation in SrTiO 3−δ from the loss of O 2− anions can be achieved by the reduction of 2δ Ti 4+ cations to Ti 3+ . The resulting defects are V O and small polarons and the anelastic spectra of SrTiO 3−δ and BaTiO 3−δ show peaks due to their hopping, with clearly distinct peaks for vacancies that are isolated and paired [38,39].…”

Section: Point Defects Relaxationsmentioning

confidence: 99%

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Cordero,

Craciun,

Imperatori

et al. 2023

Materials

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We measured the anelastic, dielectric and structural properties of the metal-free molecular perovskite (ABX3) (MDABCO)(NH4)I3, which has already been demonstrated to become ferroelectric below TC= 448 K. Both the dielectric permittivity measured in air on discs pressed from powder and the complex Young’s modulus measured on resonating bars in a vacuum show that the material starts to deteriorate with a loss of mass just above TC, introducing defects and markedly lowering TC. The elastic modulus softens by 50% when heating through the initial TC, contrary to usual ferroelectrics, which are stiffer in the paraelectric phase. This is indicative of improper ferroelectricity, in which the primary order parameter of the transition is not the electric polarization, but the orientational order of the MDABCO molecules. The degraded material presents thermally activated relaxation peaks in the elastic energy loss, whose intensities increase together with the decrease in TC. The peaks are much broader than pure Debye due to the general loss of crystallinity. This is also apparent from X-ray diffraction, but their relaxation times have parameters typical of point defects. It is argued that the major defects should be of the Schottky type, mainly due to the loss of (MDABCO)2+ and I−, leaving charge neutrality, and possibly (NH4)+ vacancies. The focus is on an anelastic relaxation process peaked around 200 K at ∼1 kHz, whose relaxation time follows the Arrhenius law with τ0 ∼ 10−13 s and E≃0.4 eV. This peak is attributed to I vacancies (VX) hopping around MDABCO vacancies (VA), and its intensity presents a peculiar dependence on the temperature and content of defects. The phenomenology is thoroughly discussed in terms of lattice disorder introduced by defects and partition of VX among sites that are far from and close to the cation vacancies. A method is proposed for calculating the relative concentrations of VX, that are untrapped, paired with VA or forming VX–VA–VX complexes.

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Kinetics of phase transitions and amplitude dependences of Q−1 in Na0.875Li0.125NbO3

Гриднев

Belousov

Резниченко

et al. 2022

Journal of Alloys and Compounds

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Hopping and clustering of oxygen vacancies in BaTiO3− and the influence of the off-centred Ti atoms

Cited by 14 publications

References 65 publications

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO₃ Thin Films

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO₃ Thin Films

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Kinetics of phase transitions and amplitude dependences of Q−1 in Na0.875Li0.125NbO3

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Hopping and clustering of oxygen vacancies in BaTiO3− and the influence of the off-centred Ti atoms

Cited by 14 publications

References 65 publications

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO3 Thin Films

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO3 Thin Films

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Kinetics of phase transitions and amplitude dependences of Q−1 in Na0.875Li0.125NbO3

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Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO₃ Thin Films

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO₃ Thin Films