EXAFS INVESTIGATION OF THE NI2-METAL FLUORIDE GLASSES( ENVIRONMENT INHEAVY)

The nickel local structure of Ni doped heavy metal fluoride glasses of the type ZrF4-BaF2-LaF3-NaF-(BaCl2) as a function of the chlorine con tent has been determined by means of x-ray absorption spectroscopy. Ni ckel ion is surrounded by six halides in octahedral configuration in a ll the samples studied. At low chlorine content nickel is coordinated only by fluorine, at intermediate concentrations Ni coordinate three f luorine and three chlorine presumably in trigonal symmetry and at high Cl concentrations by only six chlorine. Our results correlates with t he optical absorption spectra of Ni2+ which shows that the E-1 band ch aracteristic of Ni2+ coordinated by six fluorine atoms changes in shap e and energy position with the Cl content.