The luminescence of heavily-doped KCl-Tl phosphors

Excitation and emission spectra of KCl : Tl phosphors having higher Tl content (Tl ≈ 0.01 m.f. and above) were examined with the help of Aminco-Bowman spectrophotofluorometer. Measurements also included the luminescence study of TlCl powder and TlCl solution. It is observed that there is parallelism in the excitation and emission spectra of heavily-doped KCl : Tl phosphor, TlCl powder and aqueous TlCl-solution. It is concluded that heavily-doped KCl : Tl phosphor contains undissociated TlCl molecules which act as luminescence centres.