Rbsum6. -La conductivite des cristaux, purs et dopes au sodium, a kt6 mesurke B des temperatures allant jusqu'a 1 125 K, en evitant toute reaction chimique entre le fluorure de calcium et la vapeur d'eau residuelle, ou l'oxygkne. Les donnees ont kt6 analysks a l'aide de techniques des moindres carres non lineaires pour obtenir des valeurs numeriques des paramktres gouvernant la formation et la migration des dkfauts. Ces resultats sont comparQ avec des travaux experimentaux et theoriques anttrieurs, et montrent que la valeur probable de l'bnergie de formation des defauts de Frenkel dans le sous-reseau d'anions est 2,7 eV et que les energies de migration des lacunes et des interstitiels anioniques se situent respectivement dans les intervalles 0,35-0,55 eV et 0,78-0,92 eV.Abstract. -The ionic conductivity of pure and sodium doped calcium fluoride crystals has been measured at temperatures up to 1 125 K, avoiding chemical reaction of the calcium fluoride with residual water vapour or oxygen. The data have been analyzed using non-linear least squares techniques to yield numerical values of the parameters governing the formation and migration of defects. These results are compared with previous experimental and theoretical work and show that the probable value of the formation energy of Frenkel defects on the anion sub-lattice is 2.7 eV and that the migration energies of anion vacancies and interstitials lie in the ranges 0.35-0.55 eV and 0.78-0.92 eV, respectively.
The defect complexes formed when the univalent metal ions Na+ or K+ are incorporated in CaF2, SrF2, or BaF2 have been investigated by the technique of thermal depolarization. Only a single depolarization event is found in CaF2:Na+ and SrF2:Na+ and this is ascribed to nearest neighbour Nas+Fv− complexes (s = substitutional ion, v = vacancy). Evidence for this kind of complex is also observed in BaF2:K+ and a second depolarization peak at 138 K in these crystals is attributed to an M+ impurity.
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