Luminescence and Electrical Conductivity associated with Defects in Alkali Halide Crystals

Ewles, J.; Stead, J C

doi:10.1088/0370-1301/69/3/314

Cited by 6 publications

(6 citation statements)

References 3 publications

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“…The enhancement of the conductivity (as compared with an annealed specimen) and by Ewles & Stead (1956) was confirmed. The initial excess conductivity ^responds to a concentration of therm ally produced vacancies exceeding the ( uilibrium concentration a t room tem perature by a factor of the order of 1012, iid was found to decay a t all tem peratures a t rates independent of the applied d. and of the size and shape of the specimen.…”

Section: E Xperim Ental Resultsmentioning

confidence: 66%

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Diffusion of negative ion vacancies in potassium chloride

Ewles

Jain

1958

Proc. R. Soc. Lond. A

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The results of experimental investigations on the rate of relaxation of the enhanced electrical conductivity produced by rapid quenching of potassium chloride are shown to be in good agreement with the theoretical findings of Jain (1958) for the rate of annihilation of lattice vacancies by diffusion to surfaces. The rate of relaxation is found to be independent of the size and shape of specimen, suggesting that the surfaces at which annihilation occurs are those of a submicroscopic structure. The temperature and time dependence of the relaxation together with the theory permit the evaluation of the diffusion coefficient for negative ion vacancies ( D 0 ~ 7 cm 2 s -1 ) for potassium chloride, their energy of migration (1·86 eV) and the order of the dimensions of the mosaic blocks (10 -5 cm).

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Section: E Xperim Ental Resultsmentioning

confidence: 66%

“…has already been reported th a t sudden quenching of alkali halide crystals from ihigh tem perature produces an ionic conductivity in excess of the normal equiarium value for a given tem perature (Ewles & Stead 1956). This excess conactivity slowly decays w ith time.…”

Section: Introductionmentioning

confidence: 95%

Diffusion of negative ion vacancies in potassium chloride

Ewles

Jain

1958

Proc. R. Soc. Lond. A

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“…The pressure and stimulation effects were IOC 9C 7o 6o 50 4o 20 10 .i ? After O3 firing the samples had a deep brown body color.…”

Section: Research Department Westinghouse Electric Corporation Bloomentioning

confidence: 97%

“…Less well known are the stimulating and quenching effects due to higher-energy radiation, i.e., x-rays, gamma rays, cathode rays, and ultraviolet (3)(4)(5)(6)(7). Kats (8) and Ewles and co-workers (9)(10)(11) have reported on luminescence effects in alkali-halide and alkaline-earth oxides due to grinding. That is, it is not necessary for them to be ground, crushed, surface-treated, etc.…”

Section: Research Department Westinghouse Electric Corporation Bloomentioning

confidence: 99%

Two Unusual Effects in H2-fired CaO:Mn,Li Phosphors

Joffe

1962

J. Electrochem. Soc.

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For all the crystals investigated, the spectral distribution was independent of voltage except for the small shift of the whole spectrum mentioned above. The same result was obtained by Mattler and Ceva (10) on electroluminescent ZnS:Cu phosphor powders. These facts have to be taken into account in any theory on EL excitation as they imply that the SchSn-Klasens model of luminescence centers, and the theory of direct impact-ionization of the centers by accelerated electrons cannot be correct simultaneously. On these assumptions, the intensity of the blue emission should increase more steeply with voltage than that of the green one. Therefore, on the basis of the SchSn-Klasens model one has either to discard impact-ionization altogether, or to assume that the impacts liberate valence-band electrons and not those in the different centers. If, however, future experiments and theory should further substantiate the direct impact-ionization theory, the SchSn-Klasens model will have to be modified. Such a modification, which takes into account the results of Mattler and Ceva (1O), was proposed by Curie (4). ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 193.61.135.80 Downloaded on 2015-03-11 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 193.61.135.80 Downloaded on 2015-03-11 to IP

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“…At one time Seitz [l] suggested the antimorph of the F-center as the defect responsible for the V, absorption band in 1021, but there has been no subsequent confirmation. Ewles and co-workers [2] have postulated the vacated cation site as the defect responsible for some absorption and luminescence bands in KC1 and NaCI, but subsequent investigations by the same group [3] using thermoluminescence techniques placed considerable doubt on the earlier interpretation. Using electron paramagnetic resonance (EPR), Kanzig [4] has identified the antimorph of the F-center (V,) in X-irradiated Lip.…”

Section: Introductionmentioning

confidence: 99%

Quenched‐in Photoluminescent Color Centers in NaI

Fontana¹,

Sciver²

1970

Physica Status Solidi (b)

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by rapid immersion in liquid nitrogen. I n the case of NaI, very strong absorption bands at 255 nm (Q1) and 226 nm (Q2) may be produced by quenching the crystal from about 360 "C. The excitation spectrum for a characteristic luminescence a t 375 nm, is identical, within the limits of experimental accuracy, with bands produced by stoichiometric excess iodine. Similar results were obtained for quenched K I , although the luminescent quantum efficiency was smaller. Negative results were obtained for quenched KCl. Analysis of the observed properties leads to the conclusion that the defect responsible for the 375 nm luminescence is, or is related to, the single cation vacancy.NaJ-, K J -und KC1-Kristalle werden von Temperaturen bis z u 450 "C durch schnelles Eintauchen in flussigen Stickstoff abgeschreckt. Fur NaJ konnten starke Absorptionsbanden bei 255 nm (Q1) und 226 nm (Q2) durch Abschrecken des Kristalls von etwa 360 "C erhalten werden. Das Anregungsspektrum fur eine charakteristische Lumineszenz bei 375 nm ist innerhalb der Fehlergrenzen..identisch mit Banden, die durch stochiometrisch uberschussiges Jod verursacht werden. Ahnliche Ergebnisse wurden fur abgeschrecktes K J erhalten, obgleich die Quantenausbeute der Lumineszenz kleiner war. Negative Ergebnisse wurden fur abgeschrecktes KCI erhalten. Eine Analyse der beobachteten Eigenschaften fuhrte zu der Annahme, daB die fur die 375 nm-Lumineszenz verantwortlichcn Defekte isolierte Kationenlucken sind oder mit diesen zusammenhangen.

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Luminescence and Electrical Conductivity associated with Defects in Alkali Halide Crystals

Cited by 6 publications

References 3 publications

Diffusion of negative ion vacancies in potassium chloride

Diffusion of negative ion vacancies in potassium chloride

Two Unusual Effects in H2-fired CaO:Mn,Li Phosphors

Quenched‐in Photoluminescent Color Centers in NaI

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