A Study of the Effect of Deformation on the ESR, Luminescence, and Absorption of MgO Single Crystals

Abstract

The effect of plastic deformation on the optical absorption, ESR, and thermoluminescent properties of MgO has been investigated. Plastic deformation produces an optical absorption band a t about 217 nm whose intensity is proportional to the percent of deformation.No new ESR signals were detected in the deformed crystals. When deformed crystals are irradiated with 6oCo y-rays, however, the ESR signal from the F-center is observed and several new optical absorption bands also appear. Impurity ion ESR signals in y-irradiated samples have been compared with thermoluminescence spectra. The results indicate that the blue thermoluminescence a t 3.3 eV and 85 "C is due to Fez+ converting to Fe3+ and the red thermoluminescence a t 1.7 eV and 85 "C is due to the formation of Cr3+.Es wird der EinfluS einer plastischen Verformung auf die optische Absorption, ESR und thermische Lumineszenz von MgO untersucht. Die plastische Deformation erzeugt optische Absorption bei 217 nm, deren StLrke direkt proportional zur Verformung ist. I n den verformten Kristallen wurden keine neuen ESR-Signale gefunden. Jedoch wurden ESR-Signale von F-Zentren und verschiedene neue optische Bander beobachtet, wenn die deformierten Kristalle y-bestrahlt wurden. Die ESR-Signale von Fremdionen in den y-bestrahlten Proben wurden mit den thermischen Lumineszenzspektren verglichen. Die Ergebnisse weisen darauf hin, da8 die blaue Lumineszenz bei 3,3 eV und 85 "C beim Ubergang von Fez+ in Fe3+ nnd die rote bei 1,7 eV und 85 "C bei der Bildung von Cr3+ entsteht.

A Study of the Effect of Deformation on Optical Absorption of MgO Single Crystals

“…It can be seen that in the region of the V band the spectra in and out of the band are essentially the same. However, the bands at 4.07 and 5.75 eV, first observed by Sibley et al [7], are quite different. The focus of this paper is the band a t 4.07 eV and a related band at As we consider dislocation interactions which may produce such anisotropic point defects, it is important to measure the absorption through the three mutually perpendicular (100) faces of the specimen and t o relate these faces to the active slip system or systems which operated in deformation.…”

“…Other evidence for this lowering of symmetry comes from the transition energy. Sibley et al [7] first reported the band a t 4.00 eV. We have observed it from 4.00 t o 4.12 eV, but most often a t 4.07 eV.…”

“…The impetus for the present study comes from the absorption work of Sibley et al [7] on deformed crystals of MgO. They found that if the deformed crystals were y-irradiated, I?+ centers could be detected by spin resonance, indicating the presence of anion vacancies.…”

SEM cathodoluminescence studies of heat-treated MgO crystals

“…In MgO the presence of negative-ion vacancies (*) Present address : Dept of Physics, University of the West Indies, Jamaica. after deformation is certain from the observation of F + colour centres (oxygen-ion vacancies occupied by single electrons) [4,5], However, Velednitskaya et al [6] believe that the blue CL rosette pattern around indentations is due to interstitial defects but Newton and Sibley [7] argue that vacancy loops, which have been observed in damaged MgO, would probably annihilate any interstitial clusters formed. Pennycook et al [8] produced evidence indicating that much of the CL around an indentation can be associated with dislocations.…”

“…Pennycook et al [8] produced evidence indicating that much of the CL around an indentation can be associated with dislocations. Sibley et al [4] reported that the blue thermoluminescence (TL) in y-irradiated MgO was due to Fe 3+ impurity ions but Ziniker et al [9] found no blue TL emission in either relatively pure or iron doped MgO and Newton and Sibley [7] later demonstrated that the blue TL was associated with deformation accidentally introduced during sample preparation.…”