Depolarization currents in Al2O3 and MgAl2O4 oxides

Carvalhaes, Roberto Paiva Magalhães; Rocha, M S F da; Souza, Saulo Soares de; Blak, Ana Regina

doi:10.1016/j.nimb.2003.12.031

Cited by 9 publications

(7 citation statements)

References 14 publications

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“…Optical absorption results indicate that the presence of bands of water molecules in the infrared region obstruct the appearance of the TSDC bands in both Al 2 O 3 and MgAl 2 O 4 . The 250 K peak in MgAl 2 O 4 was correlated to Vtype centres, and the 250 K peak in Al 2 O 3 to a substitutional Mg 2+ ion near a trapped hole localised on an adjacent oxygen ion [163].…”

Section: Natural and Synthetic Amorphous And Crystalline Solidsmentioning

confidence: 96%

“…Carvalhaes et al [163] studied dipole defects in γ-irradiated and thermally treated samples of Al 2 O 3 , are related to dipole defects. The other bands are possibly related to different types of charge storage mechanisms (space-charge and interfacial polarisation), or deal with distributions in activation energies and/or relaxation times.…”

Section: Natural and Synthetic Amorphous And Crystalline Solidsmentioning

confidence: 99%

See 1 more Smart Citation

TSDC spectroscopy of relaxational and interfacial phenomena

Gun'ko

Zarko

Goncharuk

et al. 2007

Advances in Colloid and Interface Science

134

167

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Section: Natural and Synthetic Amorphous And Crystalline Solidsmentioning

confidence: 96%

Section: Natural and Synthetic Amorphous And Crystalline Solidsmentioning

confidence: 99%

TSDC spectroscopy of relaxational and interfacial phenomena

Gun'ko

Zarko

Goncharuk

et al. 2007

Advances in Colloid and Interface Science

134

167

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“…A. Ibarra and R. Vila from CIEMAT (Madrid, Spain) and Dr. J. R. Martinelli from IPEN (São Paulo, Brazil). The samples impurity content has already been published previously [6].…”

Section: +mentioning

confidence: 99%

Optical absorption, paramagnetic resonance and depolarisation currents in MgAl₂O₄ spinel

Paiva

Carvalhaes

Blak

2007

Phys. Status Solidi (c)

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Optical Absorption (OA), Electron Paramagnetic Resonance (EPR) and Thermally Stimulated Depolarisation Currents (TSDC) techniques were applied to study the effects of irradiation and thermal treatments in the formation, aggregation and destruction processes of dipole defects in MgAl 2 O 4 spinel. Irradiated MgAl 2 O 4 crystals present two OA bands centred at 3.4 eV and 5.1 eV. The 3.4 eV band increases with the irradiation-dose, stabilizes its maximum height for doses near 10 kGy and is completely destroyed for thermal treatments above 500 K. This same band decays when the sample is maintained at room temperature reaching a constant value after a few weeks. The EPR spectrum is composed by two superimposed bands at g = 2.011. The gamma dose dependence, the thermal treatments between 370 K and 500 K and the thermal decay of the two bands at room temperature, show that each band behaves in a different way thus indicating that they are associated with two different defects. Gamma dose of 10 kGy produces a TSDC band at 245 K. When the sample is maintained at room temperature, after the gamma irradiation, for several weeks, a displacement in the peak position to 290 K, is observed. Thermal treatments above 500 K destroy the 290 K band. This band is associated to at least two V-type centres.

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“…All dopants enhance the efficiency of defect creation in spinel. Thermally stimulated depolarisation currents (TSDC) measurements in MgAl 2 O 4 spinels doped with Fe, Cr, Mn and Co after thermal treatments and γ-irradiation show two bands of dipole origin at 160K and 290K, the first one attributed to intrinsic defects originated from the interchange of Mg 2+ and Al 3+ sites and the second one to V-type centres [7][8][9]. Computer simulation is a powerful tool to study all the possible defect formation mechanisms in materials.…”

Section: Introductionmentioning

confidence: 99%

Characterization of dipole defects in MgAl ₂ O ₄ spinel

Carvalhaes¹,

Rocha²,

Souza³

et al. 2005

phys. stat. sol. (c)

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PACS 61.80.Ed, 61.82.Ms Dipole defects in gamma-irradiated and thermal treated MgAl 2 O 4 samples have been studied through thermally stimulated depolarisation currents(TSDC) technique and computer modelling methods. The presence of TSDC bands varies from sample to sample and some crystals do not present any band. The origin of these bands has been investigated in several different samples. In the spectra of spinels showing TSDC peaks, three bands at 130K, 160K and 320K are observed. The peaks at 130K and 160K have been attributed to dipole defects. After 1200kGy of gamma irradiation the broad band at 320K dislocates to 290K and increases ten times. Pulsed thermal treatments between 350K and 470K produce a progressive reduction of the peak area and a shift in the peak position back to 320K. A detailed analysis of the curve indicates the possibility of a superposition of peaks. Gamma irradiation restores the 320K TSDC peak. Taking into account optical absorption(OA) and electron paramagnetic resonance(EPR) results, the thermal reduction of the 320K TSDC band was attributed to V-type centres as a result of hole trapping at tetrahedral and octahedral cation vacancies. Computer modelling methods, based on lattice energy and defect minimisation, were applied to identify dipole defects that occur in these crystals. The calculations were made in normal and inverse spinel structures, doped with Cr, Co, Mn and Fe in order to justify the presence of dipole bands.

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Depolarization currents in Al2O3 and MgAl2O4 oxides

Cited by 9 publications

References 14 publications

TSDC spectroscopy of relaxational and interfacial phenomena

TSDC spectroscopy of relaxational and interfacial phenomena

Optical absorption, paramagnetic resonance and depolarisation currents in MgAl₂O₄ spinel

Characterization of dipole defects in MgAl ₂ O ₄ spinel

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Depolarization currents in Al2O3 and MgAl2O4 oxides

Cited by 9 publications

References 14 publications

TSDC spectroscopy of relaxational and interfacial phenomena

TSDC spectroscopy of relaxational and interfacial phenomena

Optical absorption, paramagnetic resonance and depolarisation currents in MgAl2O4 spinel

Characterization of dipole defects in MgAl 2 O 4 spinel

Contact Info

Product

Resources

About

Optical absorption, paramagnetic resonance and depolarisation currents in MgAl₂O₄ spinel

Characterization of dipole defects in MgAl ₂ O ₄ spinel