Numerical simulation of the defect chemistry and electrostatics at grain boundaries in titanate ceramics

Hagenbeck, R.; Schneider-Störmann, Ludger; Vollmann, M.; Waser, Rainer

doi:10.1016/0921-5107(96)01584-x

Cited by 33 publications

(18 citation statements)

References 16 publications

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“…Figures 8(a) and (b) shows a schematic diagram of the profile of acceptor dopant (A′) and the grain boundary donor‐like surface charge (D • ) for the fine‐ and coarse‐grain samples, respectively. It is well known that acceptor dopants have a strong tendency to segregate in the grain boundary region due to a positive grain boundary surface charge (D • ), that is, high temperature space charge potential 29–31 …”

Section: Resultsmentioning

confidence: 99%

“…When the grain growth does not occur at low sintering temperatures most of the added acceptor dopants will be incorporated in the grain boundary region ([A′] GB ) and the solid state diffusion of dopants into the interior of grain is usually very limited 32 . The acceptors incorporated in the grain boundary region ([A′] GB ) are supposed to be charge‐compensated by part of the grain boundary donor like surface charges ([D • ]) 15,30 . Therefore, it would limit the ionic compensation of [A′]≈2[V O •• ] that dominates the conductivity in the coarse‐grain materials.…”

Section: Resultsmentioning

confidence: 99%

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Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO₃Ceramics

Yoon

Randall

Hur

2009

Journal of the American Ceramic Society

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The effect of acceptor concentration in (Mg)‐doped BaTiO3 on the resistance degradation behavior was contrasted between coarse‐ and fine‐grain samples with ∼90 and ∼0.8 μm in size, respectively. Both cases showed similar trends that the time to degradation decreased systematically with the increase of acceptor concentration, however the absolute rates are very different for a given dopant concentration. Although the grain size and grain boundaries are important, it is also shown through an impedance analysis that the degradation behavior depends on the grain conductivity (σg) and ionic transference number (tion) as evaluated by the Warburg impedance. Under the condition of the same nominal acceptor concentration, fine‐grain samples showed much lower grain conductivity (σg) but little differences in the grain boundary conductivity (σgb) than that of coarse‐grain samples. The ionic transference number (tion) was also much smaller in fine‐grain samples. These results show that the actual effective acceptor concentration on being ionically compensated to enhance oxygen vacancies becomes smaller with the decrease of grain size. This fact coupled to the increase of the number of grain boundaries accounts for the improved degradation behavior with the decrease of grain size.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO₃Ceramics

Yoon

Randall

Hur

2009

Journal of the American Ceramic Society

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“…Parts of the cation vacancies in BaTiO 3 or SrTiO 3 may exist as partially ionized states ͑V Ba Ј , V Sr Ј , and V Ti ٞ͒ at high temperatures, and become fully ionized states (V Ba Љ , V Sr Љ , and V Ti ЉЉ͒ trapping electrons when specimens are cooled to room temperature. [7][8][9][10][11]22 The reported values of the cation vacancies' energy levels from the bottom of the conduction band are 1.8 or 1.3 eV for V Ba Љ , 1.3 or 1.14 eV for V Ti ЉЉ etc. 20,[23][24][25] The bulk Fermi energy level is expressed as…”

Section: B Theoretical Calculation Of Electron and Each Defect Concementioning

confidence: 98%

Effect of donor (Nb) concentration on the bulk electrical resistivity of Nb-doped barium titanate

Yoon¹,

Kim²

2002

Journal of Applied Physics

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The behavior of the bulk electrical resistivity of donor-doped BaTiO3 with the increase of donor concentration was investigated. A series of coarse-grained specimens with different donor concentrations were prepared by adjusting the oxygen partial pressure during sintering. Then they were heat treated in air for an extended period in order to reach the equilibrium defect distribution corresponding to each heating temperature, which was followed by fast cooling. The critical donor concentrations, beyond which the bulk resistivity increases abruptly, were experimentally evaluated and they were found to decrease with a decrease in the equilibrium temperature in air. Each defect and electron concentrations as a function of donor concentration were theoretically calculated based on the model that the resistivity anomaly is caused by the partially ionized cation vacancies (VTi‴) at high temperature, which trap electrons, and become fully ionized cation vacancies (VTi⁗) as specimens are cooled to room temperature. The results calculated could explain the experimentally observed behavior of the bulk resistivity versus donor concentration.

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“…With respect to C GB , the procedure is described by Hagenbeck et al 11 In the subsequent sections of this paper, the impact of R GB will be revealed.…”

Section: (1) Electrostatics Of the Gb Regionmentioning

confidence: 99%

Grain‐Boundary Defect Chemistry of Acceptor‐Doped Titanates: Inversion Layer and Low‐Field Conduction

Vollmann

Hagenbeck

Waser

1997

Journal of the American Ceramic Society

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131

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The electronic and ionic conduction across grain-boundary (GB) space-charge depletion layers in acceptor-doped SrTiO 3 ceramics have been investigated by admittance analysis in the time domain. The dependence on the acceptor concentration, the oxygen partial pressure during equilibration, and the temperature dependence of the GB conductivity are discussed and interpreted in terms of a defect-chemistry model of the GB region using a numerical simulation technique.

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Numerical simulation of the defect chemistry and electrostatics at grain boundaries in titanate ceramics

Cited by 33 publications

References 16 publications

Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO₃Ceramics

Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO₃Ceramics

Effect of donor (Nb) concentration on the bulk electrical resistivity of Nb-doped barium titanate

Grain‐Boundary Defect Chemistry of Acceptor‐Doped Titanates: Inversion Layer and Low‐Field Conduction

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Numerical simulation of the defect chemistry and electrostatics at grain boundaries in titanate ceramics

Cited by 33 publications

References 16 publications

Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO3Ceramics

Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO3Ceramics

Effect of donor (Nb) concentration on the bulk electrical resistivity of Nb-doped barium titanate

Grain‐Boundary Defect Chemistry of Acceptor‐Doped Titanates: Inversion Layer and Low‐Field Conduction

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Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO₃Ceramics

Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO₃Ceramics