Surface segregation in ceramic materials during cooling or under a temperature gradient
✍ Scribed by G. Petot-Ervas; C. Petot
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 780 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0955-2219
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✦ Synopsis
This paper concerns the dynamic segregation of impurities in iono-covalent semiconducting compounds subject to large temperature changes. Simultaneously to the temperature gradient a chemical potential gradient takes place in these compounds. From the expression of the flux of mobile species (vacancies and cations in the considered materials ) it has been shown that segregation (or precipitation) effects must be observed near surfaces. These effects are directly related to the mobilities of the different cations. The predicted effects are consistent with segregation layer thicknesses found experimentally in ceramic materials qfter cooling.
This analysis confirms the fact that in ceramic materials the dynamic segregation effects near sur-.faces during cooling must be taken into account in the interpretation of segregation results observed at room temperature. These changes in composition near sur[aces can have important technological consequences, .[or example in ceramic powder preparation, and consequently in powder sintering or in the aging of ceramics subject to large temperature changes at high temperature.