Dichte�nderung von KCl-Kristallen durch Einbau zweiwertiger Ionen

Pick, H.; Weber, Heinrich

doi:10.1007/bf01339441

Cited by 43 publications

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“…This shows that not only are the defects generated by crushing and compression completely removed by heat treatment but also some of the defects originally present in the crystals. Incorporation of a cationic impurity having a charge different from that of the corresponding ion in the host lattice generates defects in the host lattice [25]. For example, each calcium ion incorporated into a potassium chloride lattice results in the simultaneous inclusion of a cation vacancy.…”

Section: Discussionmentioning

confidence: 99%

Role of Lattice Defects in the Annealing of Chemical Radiation Damage

Mohanty

Nair

1970

Radiochimica Acta

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Band 13, Heft 1 1970 MOHANTY and NAIR, Role of Lattice Defects by Chemical Radiation Damage 37 die Ausbeute an unbekannten Produkten leicht abfällt (vgl. Tab. 1 und 2). Deutlicher sind die quartären Effekte bei Ph 3 AsO zu erkennen. Die Ausbeute der unbekannten Produkte liegt bei höherer Gammadosis im Vakuum um 5%, in Luft sogar um 8% tiefer und die Ausbeute des freien Arsens entsprechend höher. Somit werden im Vakuum ca. 20% und in Luft ca. 35% der unbekannten Produkte, die durch sekundäre Effekte entstanden waren, durch quartäre Effekte zerstört. Die thermische Ausheilung solcher Bestrahlungsproben führt zu einer weiteren Zerstörung der unbekannten Produkte. Im Vakuum ergibt sich nach einer ca. 20stündigen Ausheilung bei 100 °C eine Abnahme der unbekannten Produkte um 50% und in Luft um 40%, die zu einer entsprechenden Zunahme der As-Ausbeuten führt. Für Ph 3 AsO können demnach weder bei den tertiären noch bei den quartären Effekten Radikalreaktionen beobachtet werden. Bei Bestrahlung in der aktiven Zone werden für vakuum-und luftbestrahlte Proben von Ph 3 As praktisch gleiche Aktivitäts-verteilungen gefunden. Die quartären Effekte führen zu einem Anstieg der Ausbeuten für die phenylgruppenhaltigen Produkte, wobei die höhere Ph 3 As-Ausbeute besonders auffällt. Da diese Radikalreaktionen in Gegenwart von Luft während der Bestrahlung genau so ablaufen wie im Vakuum, kann geschlossen werden, daß die Diffusionsgeschwindigkeit des Sauerstoffs kleiner ist als die der Radikale. Durch thermische Ausheilung werden qualitativ ähnliche tertiäre Effekte hervorgerufen wie nach Bestrahlung im VK 3, d. h. im Vakuum verlaufen Radikalreaktionen, während in Luft die Zersetzung der unbekannten Produkte dominiert.Zusammenfassend kann festgestellt werden, daß bei Ph 3 AsO lediglich sekundäre Effekte zur Ausbildung von Ph-76 As-Bindungen führen, während durch tertiäre und quartäre Effekte ein Teil der Ph-76 AsBindungen gespalten wird. Ein solches ungewöhnliches Verhalten tritt sowohl in Anwesenheit als auch in Abwesenheit eines Radikalfängers auf. Im Gegensatz dazu werden bei Ph 3 As durch tertiäre Effekte in Abwesenheit eines Radikalfängers Ph-76 As-Bindungen ausgebildet, wobei die tertiären Effekte schon bei Zimmertemperatur mit merklicher Geschwindigkeit ablaufen. Die Anwesenheit eines Radikalfängers verändert den Charakter der tertiären Effekte in Ph 3 As, es werden dann vorwiegend C-76 As-Bindungen gespalten. Durch quartäre Effekte erhöht sich in jedem Falle der Anteil an C-76 As-Bindungen.Für bereitwillige Unterstützung bei der Durchführung der Bestrahlungen bedanken wir uns bei den Kollegen der Abteilung Reaktorbetrieb im ZfK Rossendorf. Unser besonderer Dank gilt Fräulein SCHEADEB für ihre hervorragende Hilfe bei Bestrahlung und Aufarbeitung der Proben. SummaryThe role of lattice defects introduced by crushing, compression, doping, and fast neutron bombardment in the annealing of y-irradiation damage in lead nitrate has been investigated. Compression and crushing of irradiated crystals produce direct recovery and also accel...

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Section: Discussionmentioning

confidence: 99%

Role of Lattice Defects in the Annealing of Chemical Radiation Damage

Mohanty

Nair

1970

Radiochimica Acta

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“…As a result, it was found that the dislocation density and the yield stress remarkably increase for the crystals quenched from the temperature (T) above 673 K. While the value of tan does not vary by quenching from the temperature below 573 K or above 673 K. In Figure 5, the values of  , tan , and τy at about 300 K correspond to the specimen A and those at 673 K the specimen A quenched from 673 K. When alkali halide crystals are doped with divalent cations, the dopant cations induce positive ion vacancies in order to conserve the electrical neutrality and are expected to be paired with the vacancies. They are often at the nearest neighbor sites forming a divalent impurity-vacancy (I-V) dipole, which attract them strongly [73], for crystals quenched from a high temperature. Then asymmetrical distortions (tetragonal lattice distortions) are produced around the I-V dipoles.…”

Section: Preparation Of Specimensmentioning

confidence: 99%

Study on Dislocation-Dopant Ions Interaction in Ionic Crystals by the Strain-Rate Cycling Test during the Blaha Effect

Kohzuki

2018

Crystals

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Abstract:The interaction between a dislocation and impurities has been investigated by measurements of yield stress and proof stress, micro-hardness tests, direct observations of dislocation, internal friction measurements, or stress relaxation tests so far. A large number of investigations has been carried out by the separation of the flow stress into effective and internal stresses on the basis of the temperature dependence of yield stress, the strain rate dependence of flow stress, and stress relaxation. Nevertheless, it is difficult to investigate the interaction between a dislocation and obstacles during plastic deformation by the mentioned methods. As for the original method which combines strain-rate cycling tests with the Blaha effect measurement, the original method is different from above-mentioned ones and would be possible to clear it up. The strain-rate cycling test during the Blaha effect measurement has successively provided the information on the dislocation motion breaking away from the strain fields around dopant ions with the help of thermal activation, and seems to separate the contributions arising from the interaction between dislocation and the point defects and those from dislocations themselves during plastic deformation of ionic crystals. Such information on dislocation motion in bulk material cannot be obtained by the widely known methods so far. Furthermore, the various deformation characteristics derived from the original method are sensitive to a change in the state of dopant ions in a specimen by heat treatment, e.g., the Gibbs free energy (G 0 ) for overcoming of the strain field around the dopant by a dislocation at absolute zero becomes small for the annealed KCl:Sr 2+ single crystal (G 0 = 0.26 eV) in comparison with that for the quenched one (G 0 = 0.39 eV).

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“…Role of lattice defects Incorporation of cationic vacancy into the host lattice by doping with a cation having a charge different from that of the corresponding ion generates defects, whose concentration is proportional to that of the dopant ion [35]. Generation of such defects provides sites for localization of electrons or holes which increase the mobility of the product of radiolysis to enhance the recombination process [36,37].…”

Section: Chemistry Of Recoverymentioning

confidence: 99%

Radiolysis and Annealing of Damage Entities in γ-Irradiated Pure and Doped NaBrO₃

Sahu

Bhatta

1994

Radiochimica Acta

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Radiolysis of pure as well as doped (Ba 2+ ) sodium bromate has been carried out at different irradiation doses. Annealing of damage BrO", BrOj and non-Br-Ox between 393.0-433.0 Κ is enhanced with increasing temperature, irradiation dose as well as by cation doping. Analysing the data in the light of theories of diffusion controlled mechanisms, it is indicated that for each fragment recovery is a combination of one first order and one second order process. The Ζ vs. φ plots are linear in the initial period of recombination suggesting the validity of Smoluchowski boundary condition (SBC) theory.

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Dichte�nderung von KCl-Kristallen durch Einbau zweiwertiger Ionen

Cited by 43 publications

References 1 publication

Role of Lattice Defects in the Annealing of Chemical Radiation Damage

Role of Lattice Defects in the Annealing of Chemical Radiation Damage

Study on Dislocation-Dopant Ions Interaction in Ionic Crystals by the Strain-Rate Cycling Test during the Blaha Effect

Radiolysis and Annealing of Damage Entities in γ-Irradiated Pure and Doped NaBrO₃

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Dichte�nderung von KCl-Kristallen durch Einbau zweiwertiger Ionen

Cited by 43 publications

References 1 publication

Role of Lattice Defects in the Annealing of Chemical Radiation Damage

Role of Lattice Defects in the Annealing of Chemical Radiation Damage

Study on Dislocation-Dopant Ions Interaction in Ionic Crystals by the Strain-Rate Cycling Test during the Blaha Effect

Radiolysis and Annealing of Damage Entities in γ-Irradiated Pure and Doped NaBrO3

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Radiolysis and Annealing of Damage Entities in γ-Irradiated Pure and Doped NaBrO₃