Effect of preliminary low-temperature annealing on the kinetics of nucleation |
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Authors: | Valov P M Le?man V I Maksimov M V Derkacheva O Yu |
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Institution: | (1) National Institute of Chemistry, Ljubljana, Slovenia;(2) Center for Advanced Materials Processing, P.O. Box 5814, Potsdam , NY, 13699, USA; |
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Abstract: | The changes observed in the kinetics of CuCl nucleation in glass due to preliminary low-temperature annealing have been investigated
using optical spectroscopy. The influence of the number of nuclei formed at a temperature of 500°C on the growth rate of the
CuCl phase at 650°C has been examined. The amount of the CuCl phase in the sample is determined from the optical absorption
coefficient in the range of band-to-band transitions in the CuCl nanocrystals. The average radius of CuCl particles is calculated
from the position of the maximum of the exciton band. It has been demonstrated that the preliminary formation of CuCl nuclei
at 500°C for 3 h makes it possible to increase the growth rate of the CuCl phase by a factor of 6. In the sample with preliminarily
formed nuclei, there occur two opposite processes: thermal decomposition of part of the small nuclei, which have become subcritical
at 650°C; and the growth of larger nuclei, which have become supercritical at 650°C due to the diffusive inflow of the components
of the new phase. When the equilibrium concentration is reached, the new phase contains particles with a smaller radius but
at a higher concentration as compared to those in the case of the conventional nucleation at 650°C. |
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