INTERACTIONS OF POINT DEFECTS WITH DISLOCATIONS AND SURFACES IN SILVER HALIDE CRYSTALSReport as inadecuate




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Abstract : Two aspects of defect interactions in AgCl and AgBr are discussed. 1 The establishment of equilibrium between charged jogs on surfaces and dislocations and point defects produces surface charges, space charge regions, and local changes in electric potential and defect concentration. The locus and environment of the jogs play a large role in determining the nature of the space charge. For the silver halides, irnplications of these effects to the photographic process are discussed. The available information on the space charges at surfaces and dislocations in both AgBr and AgCl is surveyed ; it is seen that whereas it is energetically cheaper to produce an interstitial Ag+ than a vacancy at a surface jog, the opposite may be true at dislocations. 2 Internal friction techniques have been used to study the binding of solutes to dislocations. In AgCl, the binding energy is approximately 0.2 eV. After a srnall perturbation of the Maxwell atmosphere around the dislocation, the recovery follows a t1-3 law ; a simple model yields this dependence, and also the correct activation energy. Similar studies in AgBr, however, have revealed a strange regime in which the rate constant for recovery has a negative activation energy, the magnitude and temperature range of the effect depending on concentration of dopant. No simple explanation is yet available.





Author: L. Slifkin

Source: https://hal.archives-ouvertes.fr/



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