Nucleation Processes in NaCl:Pb studied by means of ITC and Optical Absorption Spectra

Pubblicazione
Comunicazione al Congresso Inernazionale di Dublino. Agosto/Settembre 1982, pubblicato in
“Radiation effects and defects in solids”, 1983, Vol.75, pag. 93-103, Gordon and Breach Science Publishers, Inc. Printed in Great Britain. DOI: 10.1080/00337578308224688

Autori
R.Capelletti, C.Mora, E.Zecchi
Istituto di Fisica dell’Università, Via Massimo d’Azeglio 85, 43100 Parma, Italy. Gruppo Nazionale di Struttura della Materia del CNR.
O. Carranza Torres.
Departamento de Fisica. Facultad de Ingegnieria y Arquitectura, Universitat de El Salvador, El Salvador.

Presented at the Fourth Europhysical Topical Conference on “Lattice Defects in Ionic Crystals”, Dublin, Ireland, 1982.

Abstract
By exploiting the ITC technique sensitivity and versatility, we have studied:
1) The detailed kinetics of nucleation and growth of the occlusions (possibly of Suzuki phase or of its precursors), at the epxense of impurity-vacancy (IV) dipoles, induced by very long annealing at 225° of NaCl samples, moderately doped with Pb and OH⁻ free;
2) The nature of the huge ITC band, which cannot be attributed to point dipole relaxation, but rather to an interfacial ionic polarization, built up at the boundary between the host NaCl matrix and the growing occlusions;
3) The motion parameters of the new ITC band in the frame of the Maxwell-Wagner-Sillars theory.
The dielectric measurements were also continuously correlated with optical absorption spectra (taken at 10 K), which turned out to be considerably affected by the nucleation process. The results obtained are discussed also in terms of Ostwald ripening and compared with those obtained previously in KCI: Pb system.