Optical Property and Local Environment of Ni2+ in Fluoride Glasses

Optical absorption and extended X-ray absorption fine structure (EXAFS) spectra were measured on series of ZrF4−BaF2−LaF3, ZrF4−BaF2−MF−LaF3 (M; Li, Na, K, Rb, or Cs) and AlF3−BaF2−CaF2−YF3 glasses doped with Ni2+. The optical absorption spectra show that Ni2+ ions in all the glasses exist in octahedral coordination sites with six F- ions. The values of ligand field strength, 10Dq, were obtained from the optical absorption spectra, and Ni−F interatomic distances, rNi-F, were determined by EXAFS analyses. The linear relationship between 10Dq and rNi-F is found and interpreted by simple ligand field theory. The compositional dependence of the 10Dq and rNi-F is discussed in terms of the basicity of glasses. We discuss the optical property and the local environment of Ni2+ in the fluoride glasses in comparison with those of oxide glasses.