Abstract
The peak position and half-widths of bands characteristic of lead impurity in four alkali halides, NaCl, KCl, KBr and KI, are reported. Ionic conductivity studies have been made in the temperature range 150–600°C in the four alkali halides doped with Pb. The values of the energy of association of Pb ++ with a cation vacancy is ∼0.28 eV. The growth rate of F-centers in X-irradiated crystals is found to be slower in all lead doped crystals. On additive or electrolytic coloration the lead band (characterised as the A band) disappears and an intense broad (half-width 2.5 eV) ultraviolet band, besides the F band, is observed. Quenching from temperatures greater than 500°C bleaches the F band and the UV band and a new band peaking at 240–265 nm with half-width 1.4∼1.5 eV is observed in four alkali halides. Preliminary EPR measurements did not show any influence of the lead bands on the EPR results.
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