Dielectric losses of alkaline earth doped KCl and NaCl crystals containing z centers

Results of measurements of the temperature dependence of dielektric losses (tan δ) in KCl:SrCl₂, KCl:CaCl₂ and NaCl:CaCl₂ samples after electrolytic coloration, after F → Z₁ conversion and Z₁ → Z₂ conversion are reported. In agreement with Rosenberger-Lüty model, Z₁ centers display dipolar character due to the presence of the ordinary Me²⁺-cation vacancy dipole with adjacent F center. The changes of tan δ after Z₁ → Z₂ conversion point to the release of a free cation vacancy from the former dipole.