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1 Jan 1962

Volume 33, Issue 1, pp. 1-518

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Climb of Dislocations in Magnesium Oxide

G. W. Groves and A. Kelly

J. Appl. Phys. 33, 456 (1962); http://dx.doi.org/10.1063/1.1777141 (5 pages) | Cited 28 times

Online Publication Date: 11 June 2004

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Detailed electron microscope observations of plastically deformed and annealed magnesium oxide have been made. After cold work the material contains trails of elongated prismatic dislocation loops, of which the majority corresponds to a sheet of interstitial ions. On annealing at temperatures between 850° and 1600°C these trails break up into circular loops of edge dislocation and the loops then increase in size. The process occurs by the motion of vacant lattice sites along dislocation lines and possibly through the bulk material. The kinetics of the former process is described. A theory of breakup by pipe diffusion has been developed and used to obtain an activation energy for the motion of point defects in the core of a dislocation of ∼3.1 ev.

On the Theory of the Photoadsorptive Effect on Semiconductors

Th. Wolkenstein and I. V. Karpenko

J. Appl. Phys. 33, 460 (1962); http://dx.doi.org/10.1063/1.1777142 (6 pages) | Cited 7 times

Online Publication Date: 11 June 2004

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On the basis of the electron theory of chemisorption, a criterion is deduced for the positive and negative photoadsorptive effect on semiconductors (photoadsorption and photodesorption). A relation is established between the sign of the effect and the nature of the adsorbent and adsorbate, the previous treatment of the sample, and the experimental conditions (temperature and pressure). The available experimental material is analyzed and interpreted from the standpoint of the proposed theory.

Defect Structures and Transport of Matter in AgBr

A. W. Lawson

J. Appl. Phys. 33, 466 (1962); http://dx.doi.org/10.1063/1.1777143 (8 pages) | Cited 8 times

Online Publication Date: 11 June 2004

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The wide diversity of studies carried out on transport phenomena in AgBr permits a critical evaluation of the success and failures of existing theories of ion kinetics and defect equilibrium. Some unsolved problems relating to polarization, microwave dielectric constant, creep, thermoelectric power, and their relation to mobility and density of defects are discussed.

Energy and Entropy of Formation and Motion of Vacancies in NaCl and KCl Crystals

R. W. Dreyfus and A. S. Nowick

J. Appl. Phys. 33, 473 (1962); http://dx.doi.org/10.1063/1.1777144 (5 pages) | Cited 66 times

Online Publication Date: 11 June 2004

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Recent experiments on the dc ionic conductivity of NaCl crystals doped with divalent cation impurities led to a re‐evaluation of some of the basic constants for defect formation and motion in these crystals. The key parameter is the energy of motion ϵm of a cation vacancy. This parameter has been determined from the temperature dependence of the conductivity under conditions where the concentration of cation vacancies remains fixed. Such conditions apply (1) in the range just below the intrinsic region, and (2) in samples rapidly cooled to below 0°C such as to prevent the attainment of an equilibrium degree of association. From the present work combined with previous data, the jump rate of the isolated positive‐ion vacancy in NaCl is ν=12ν0 exp(−ϵm∕kT) with ν0=1014.1±0.3 sec−1 and ϵm=0.80±0.02 ev. With the aid of earlier measurements in the intrinsic range it is concluded that the energy of formation of a Schottky defect in an NaCl crystal is 2.12±0.06 ev, while the entropy of formation is 6.2±1.8 (in units of k). Very similar results, although of somewhat lower precision, apply to KCl. Finally, a comparison is made between these values and the predictions of existing theories.

Effects of Quenching and Annealing on Ionic Conductivity and on Dislocation Decorability in Silver Chloride

H. Layer, M. G. Miller, and L. Slifkin

J. Appl. Phys. 33, 478 (1962); http://dx.doi.org/10.1063/1.1777145 (4 pages) | Cited 13 times

Online Publication Date: 11 June 2004

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Pure silver chloride crystals, when cooled rapidly from high temperatures, show enhanced ionic conductivity which may be attributed to quenched‐in Schottky defects. From the annealing out of this extra conductivity one deduces that for an associated vacancy pair the binding energy is 0.42 ev and the migration energy is ≥1.0 ev. The decorability of interior dislocations by swept‐in photoelectrons is also discussed and is shown to be sensitive to the purity of the crystal.

Ionic Conduction in Zone‐Refined KCl

H. Kanzaki, K. Kido, and T. Ninomiya

J. Appl. Phys. 33, 482 (1962); http://dx.doi.org/10.1063/1.1777146 (5 pages) | Cited 21 times

Online Publication Date: 11 June 2004

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Ionic conductivity in the extrinsic range of temperature (250° to 400°C) was measured for specimens taken from a single‐crystalline ingot of KCl subjected to zone purification. The effect of dislocation density was studied in order to clarify the nature of ionic conduction in these highly purified crystals. Conductivity increased by a factor of 10 in the purest crystals by increasing dislocation density from 106 to 107 cm−2. Conductivity was decreased in the impurer crystals by increasing the density of dislocations. Comparing the results with predictions from charged dislocation theory, the value of 0.7 ev is obtained for the formation energy of positive ion vacancies.

Disorder and Oxygen Transport in Cadmium Oxide

R. Haul and D. Just

J. Appl. Phys. 33, 487 (1962); http://dx.doi.org/10.1063/1.1777147 (7 pages) | Cited 34 times

Online Publication Date: 11 June 2004

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Oxygen‐18 exchange between gaseous oxygen and cadmium oxide crystals has been studied in the temperature range 630° to 855°C. Since isotope equilibrium is not instantaneously established at the crystal surface an appropriate solution for this particular diffusion problem has been given. In this way it is possible to evaluate rate constants (K) of the phase boundary reaction as well as lattice diffusion constants (D):
math
.The influence of the ambient oxygen pressure (D∼po2−1∕5) indicates that a vacancy mechanism is operative in the diffusion of oxygen. This is substantiated by the finding that diffusion is enhanced by incorporation of Li2O. From experiments with doped crystals the fraction of vacancies can be estimated, e.g., 4.4⋅10−4 in ``pure'' CdO at 790°C and 0.16 atm O2. On the basis of thermodynamic considerations the energy of formation of defects can be estimated at 29 leaving 63 kcal∕mole for the activation energy of the diffusion process proper.
The rate constant of the phase boundary reaction increases with decreasing oxygen pressure (K∼po2−⅓) as well as with increasing Li2O addition. These findings offer a possibility for the suggestion of a mechanism of the surface exchange process.

Correlation Effects for Diffusion in Ionic Crystals

Robert J. Friauf

J. Appl. Phys. 33, 494 (1962); http://dx.doi.org/10.1063/1.1777148 (12 pages) | Cited 34 times

Online Publication Date: 11 June 2004

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Observations of the motion of ions by means of both diffusion and electrical conductivity measurements usually show deviations from the normal Einstein relation. The interpretation of these deviations often leads to a fairly detailed picture of the types of defects present and the mechanisms of their motion. A correction must always be considered because of the fact that successive jumps of a tracer atom are correlated, as first discussed by Bardeen and Herring, and the origin of this effect is shown by treating diffusion as a random walk problem. For the interstitialcy mechanism a second correction is required because the effective displacement is larger for conductivity than diffusion, and this effect is illustrated with results on AgCl and AgBr. Possible mechanisms for ionic motion in crystals with the CsCl structure are described, and the present interpretation of results for CsBr, CsI, and TlCl is discussed. It appears that vacancy pairs may make an appreciable contribution to the diffusion. Experiments for observing diffusion with an applied electric field are discussed, and an analysis is given of the problem of determining the internal electric field in such situations. If certain experimental difficulties can be overcome, this last technique should provide a powerful extension of methods of investigating the motion of ions in crystals.

On the Gyulai‐Hartly Effect in Single Crystals of Potassium Iodide at Temperatures between 77° and 297°K

V. Hovi, E. Mäntysalo, and P. Ketolainen

J. Appl. Phys. 33, 506 (1962); http://dx.doi.org/10.1063/1.1777149 (4 pages) | Cited 1 time

Online Publication Date: 11 June 2004

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The increase of the dark current caused by plastic deformation in potassium iodide crystals has been measured at temperatures between 77° and 297°K. The Gyulai‐Hartly effect was not found to be dependent on temperature in this range. The maximum current induced by the deformation decreased in repeated deformation experiments, as has also been observed at higher temperatures. At 77°K a charge flow in the opposite direction to the Gyulai‐Hartly effect was found when the load was removed. On further deformation, a charge flow in the above direction was observed, instead of the expected Gyulai‐Hartly effect. As a result of successive deformation experiments, saturation currents associated with work hardening were measured. Potassium iodide crystals containing R′ centers did not show any Gyulai‐Hartly effect at 297°K.

Properties of Lithium Hydride‐V Vacancy Formation, Cavitation, and Lithium Precipitation in Irradiated Lithium Hydride

F. E. Pretzel, W. B. Lewis, E. G. Szklarz, and D. T. Vier

J. Appl. Phys. 33, 510 (1962); http://dx.doi.org/10.1063/1.1777150 (9 pages) | Cited 6 times

Online Publication Date: 11 June 2004

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Expansion of crystals and compresses of LiH containing up to 40% LiT was observed during exposure to tritium β particles at temperatures from −196° to 400°C. Lithium metal precipitation was observed by electron paramagnetic resonance in small samples of similar composition. The results of auxiliary measurements of optical absorption, electrical conductivity and diffusion, nuclear magnetic resonance, and x‐ray lattice parameter were used to interpret the data. Expansion was primarily related to the introduction of vacancies into the LiH crystal lattice to accommodate the products of radiation damage and tritium decay, to permit the formation of bcc Li metal, and to produce cavities in the crystals at high temperatures. Radiation damage was quickly reversed at the lowest temperatures, and the primary defects observed were interstitial He3 atoms and F centers. Warming to room temperature caused aggregation of the F centers and introduced vacancies which destroyed the interstitials Periodic warming for observation further increased the net expansion to allow the formation of bcc Li metal. At higher storage temperatures, vacancy diffusion stabilized a portion of the defects produced by radiation damage with the net result that increased expansion, increased Li formation, and H2 molecular species were observed in the crystals. The expansion rates in the temperature range of increasing radiation damage gave an activation energy consistent with that obtained for vacancy diffusion. An intercomparison of expansion and bcc Li formation at 23°C gave results consistent with the radiation‐damage yield and with the formation of Li metal by a diffusion‐controlled process. Above a 300°C minimum a second increase in expansion related to cavitation was observed.
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