Oxidation/Reduction Effects on the Thermoluminescence of?-Al2O3 Single Crystals

Abstract

a-Al 2 O 3 crystals were treated in different atmospheres (reducing/oxidising) at high temperature and their optical, positron-annihilation and thermoluminescent (TL) properties were investigated. From optical absorption and positron-annihilation spectra we concluded that aluminium-vacancies were created while oxygen-vacancies were destroyed in oxidised samples indicating a Schottkytype disorder. Structural changes were correlated with TL glow curves and the origin of some TL peaks was explained.

On phosphor degradation mechanism: thermal treatment effects

“…These traps are mainly due to the delocalization of the cationic and anionic ions and therefore the formation of F and V centers. This point is particularly important for BAM where oxygen vacancies can be created in the conduction layer close to dopant ions, (Ba/ Eu-O) layer [27][28][29][30][31].…”

Suppression of oxygen diffusion by thin Al2O3 films grown on SrTiO3 studied using a monoenergetic positron beam

“…In AES for the as-deposited sample, a peak corresponding to Ti was observed. For ␣-Al 2 O 3 , Kröger 22 and Molnár et al 16 suggested that defects are introduced by oxidation or reduction, with the species and concentrations of the defects depending on impurities in Al 2 O 3 . According to their results, for Ti-doped Al 2 O 3 , Al vacancies are introduced through the oxidation of Ti 3+ :1/2O 2 +2Ti Al…”

“…The resultant change in the Doppler broadening spectra is characterized by the S parameter, which mainly reflects the change due to the annihilation of positron-electron pairs with a low-momentum distribution, and by the W parameter, which mainly reflects the change due to the annihilation of positron-electron pairs with a highmomentum distribution. Point defects or open spaces in transition-metal oxides have been investigated by applying positron annihilation, [11][12][13][14][15][16][17][18][19][20] and the results show that positrons make a useful probe for studying vacancy-type defects in such materials.…”

Melt processing of alumina in graphite ambient for dosimetric applications

“…As a result, wide variations in the TL response of samples have been observed [7,8]. We have recently reported an alternative approach for the synthesis of dosimetry-grade Al 2 O 3 :C, in which a pure Al 2 O 3 crystal is heated to temperatures of $1500 1C in the graphite environment and vacuum [9][10][11].…”