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Diffusion of Divalent Impurities from the Volume to the Surface in NaCl Crystals

✍ Scribed by M. J. Yacamán

Publisher
John Wiley and Sons
Year
1973
Tongue
English
Weight
417 KB
Volume
56
Category
Article
ISSN
0370-1972

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✦ Synopsis

Abstract

In NaCl: Ca^2+^, NaCl: Cd^2+^, and NaCl: Cu^2+^ crystals heated in air at temperatures of 400 to 450 °C during 6 to 12 h the impurities tend to migrate to the crystal surface. There the impurities react with air and a new phase is produced on the NaCl surface. Both, transmission and scanning electron microscopy is used to study the structure and characteristics of the new phase. It is found that for NaCl: Ca^2+^ and NaCl: Cd^2+^ the new phase corresponds to CaO and CdO, respectively. The phenomenon is discussed using the theory of a double electrical layer that arises in the vicinity of the surface in ionic crystals. However this theory can not explain it completely. Diffusion to the surface must be taken into account in every work that involves a thermal treatment of a ionic crystal containing divalent impurities.

📜 SIMILAR VOLUMES

The association energy of aggregates of
The association energy of aggregates of divalent impurities and vacancies in NaCl-type crystals (point charge approximation)
✍ Dr. G. Berg; Dozent Dr. habil. F. Fröhlich; S. Siebenhüner 📂 Article 📅 1975 🏛 John Wiley and Sons 🌐 English ⚖ 286 KB 👁 2 views

## Abstract The formation and association energies for the different aggregates of divalent metal impurities and cation vacancies are derived by considerations of the sums over all lattice vectors. This gives a simple formula in the point charge approximation if an infinite lattice is assumed. Beca