Color center formation by synchrotron radiation in the Na6Al6Si6O24(Nal)(1.6) optical ceramic

The spectrum of F-center excitation by 5- to 27-eV photons in the Na6Al6Si6 O24 (NaI)(2x) sodalite optical ceramic (x = 0.8) was measured at 80 K by hi gh-sensitivity photoexcited luminescence techniques. The F centers are crea ted by photons with an energy of 5.6- to 8.5 eV through the excitation and ionization of iodine centers of two types; in the 8.2- to 27-eV region, thr ough the generation of electronic excitations in the aluminosilicate framew ork of alternating Al3+ and Si4+ ions, each coordinated tetrahedrally by ox ygen ions. At the low irradiation doses used, the F centers are created pri marily through photoelectron capture by the iodine vacancies which exist be fore irradiation. In the 23- to 25-eV region, the efficiency of F-center fo rmation doubles as a result of the multiplication of electron-hole pairs. ( C) 2001 MAIK "Nauka/Interperiodica".