|Abstract or Summary
- The incorporation of europium and dysprosium in potassium
chloride crystals was investigated. The crystals were prepared by
the Kyropoulos method from melts containing the rare-earth chlorides.
The concentration of these rare-earth ions in the crystals was determined
by neutron-activation analysis. The distribution coefficient of
europium and dysprosium between the molten and solid potassium
chloride was found to be . 21 and 1.3 x 10⁻⁴, respectively. The molar
absorptivity of europium in the KC1 crystals at two wavelengths, 241
and 325 mμ, was found to be 2880 and 2750 liter mole⁻¹ cm⁻¹, respectively.
The crystals doped with dysprosium did not exhibit any
The effect of europium, dysprosium, praseodymium, calcium,
and lead on the gamma-ray coloration of KC1 crystals was studied. It
was found that these five cations had the same qualitative effect on the coloration curve of pure KC1, although the magnitude of the effect depended
on the specific impurity. At low impurity concentrations the
total first-stage coloration was not significantly changed, however,
the rate of second-stage coloration was suppressed. As the impurity
concentration was increased further, the coloration during the first
stage increased and the second-stage coloration rate began to increase
after reaching a minimum. The minimum in the rate of the second-stage
coloration occurred at impurity concentrations below 1 x 10¹⁶
ions per cc. After the minimum in the second-stage rate of coloration
had been attained, the ratio of the total first-stage coloration to the
second-stage rate of coloration was a constant which was independent
of the impurity concentration.
Crystals of potassium chloride were grown from aqueous solutions
employing both convection and evaporation methods. The size
and the perfection of the crystals were the same for both solution-grown
methods. The dislocation density of the solution-grown crystals
was a factor of three less than crystals grown from the melt.
The solution-grown crystals exhibited lower first-stage coloration
than the melt-grown crystals, however, in the second stage the
rate of coloration was larger for the solution-grown crystals. The
second stage, which was linear for the melt-grown crystals, was
generally not linear for the solution-grown crystals.
The gamma-ray coloration of several nominally pure KCl crystals obtained from several different sources was investigated.
From this study it was suggested that the colorability can be employed
as a criterion of purity; the pure crystals will have a small first-stage
coloration and a large second-stage rate of coloration. The
ratio of the total first-stage coloration to the rate of second-stage
coloration will become smaller as the purity increases. However,
there are differences between the purity order established by the
above criterion and conductivity data.