抄録
With regard to the properties of the A-center of additively colored KBr crystals, it is described how they are modified when the crystals contain divalent cations as impurities, besides a foreign alkali impurity associated with the A-center, Na+ or Li+ ion. Divalent impurities such as Ca++ or Sr++ enhance the growth of the A-center but deteriorate the thermal stability of this center.
On the other hand, the existence of these divalent cations does not affect A′-band. The activation energies for the formation and thermal destruction of the A-center are measured as being 0.26 eV and 1.0 eV, respectively, independent of the existence of divalent ions. The ionic conductivity is increased by 50∼70 times in the vicinity of room temperature by additively coloring a sample containing Ca++ or Sr++, and is less increased in case of Ba++ or Cd++.
