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Dipole defects in Al2O3:Mg,Cr.

A R Blak1, V Gobbi, F Ayres

  • 1Instituto de Física, Departamento de Física Nuclear, Universidade de São Paulo, SP, Brazil. anablak@if.usp.br

Radiation Protection Dosimetry
|October 18, 2002
PubMed
Summary

Investigating dipole defects in Al2O3 using thermally stimulated depolarization currents (TSDC), this study identifies Mg and Cr impurities. Gamma irradiation increases a 250 K band, suggesting defect interactions with impurities.

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Area of Science:

  • Materials Science
  • Solid State Physics
  • Ceramics

Background:

  • Dipole defects in aluminum oxide (Al2O3) influence material properties.
  • Understanding these defects is crucial for optimizing ceramic applications.

Purpose of the Study:

  • To investigate dipole defects in Mg and Cr doped Al2O3 using Thermally Stimulated Depolarization Currents (TSDC).
  • To characterize the behavior of these defects under varying conditions like polarization field, gamma irradiation, and heat treatment.

Main Methods:

  • Thermally Stimulated Depolarization Currents (TSDC) technique.
  • Impurity Neutron Activation Analysis (INAA) for elemental composition.
  • Optical Absorption (OA) spectroscopy.
  • Defect simulation methods.

Main Results:

  • TSDC spectra revealed two distinct bands at 230 K and 250 K, attributed to dipole defects.
  • Band intensity correlated linearly with the polarization field, confirming dipole origin.
  • Gamma irradiation increased the 250 K band, while heat treatments up to 1400 K decreased band intensity, with partial recovery above this temperature.
  • Optical absorption showed a band at 2.6 eV linked to trapped holes near cation vacancies.
  • Defect simulations indicated a higher probability of Mg2+ substituting Al3+.

Conclusions:

  • The observed TSDC bands are attributed to dipole defects associated with Mg2+ impurities in Al2O3.
  • Gamma irradiation and thermal treatments provide insights into defect dynamics and stability.
  • Mg2+ is a likely candidate for forming dipole defects in Al2O3, impacting its electrical and optical properties.

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