Solubility and precipitation of metal impurities in alkali halide crystals: Dielectric, mössbauer and optical measurements

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Abstract
The thermodynamical equilibrium concentration of divalent impurity-vacancy dipoles in solution in different alkali halides is studied by means of ionic thermoconductivity. The activation energy of the ‘associated impurity solubility’ is of the order of 0.10 ÷ 2 eV. Mössbauer effect measurements performed on NaCl57 CoCl2, with different Co concentrations outlined that the precipitation phenomenon of divalent impunties is quite complex. The details of Mossbauer spectra are discussed. Moreover ‘charge transfer’ bands induced in optical absorption spectrum by cobalt are examined from the point of view of solution-precipitation reaction.