Ni2+ bearing fluoro-aluminoborate glass composition [(AlF3)x - (B2O3)0.63-x - (NiO)0.2 - (Na2O)0.35] was prepared
via the melt-quenching method. The structure of glass was confirmed by X-Ray diffraction patterns, density,
molar volume and infrared spectroscopy. The oxygen and fluorine bonds with the other constituent cations are
the backbone of network. Additionally, the ligand field transitions of nickel ions were assigned for octahedral and
tetrahedral forms. Unexpectedly, the addition of fluorine, mixed with oxygen, increased the splitting energy of
3d-orbitals of Ni2+ ions. This unexpected behavior is back to the influence of the high field intensity of aluminum
cations at the expense of boron cations. The splitting energy of 3d-orbitals (10Dq) increased, while interelectronic
repulsion parameters (B and C) decreased. The chemical bonding nature was evaluated. The color
variation of samples from dark brown to light brown was explained. Furthermore, the optical band gap decreased
owing to the high delocalization of electrons.