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, r(Ni-F), were determined by EXAFS analyses. The linear relationship between 10Dq and r(Ni-F) is found and interpreted by simple ligand field theory, The compositional dependence of the 10Dq and r(Ni-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.