Investigation of structural and optical properties of Ni2+ ions-bearing borate glass through barium ions addition

Nickel-bearing borate glass is regarded as a smart source for miniaturized optical applications. However, their
way of tailoring the practical applications needs more specific investigations. Here, we report structural and
optical investigation of BCaNi glass prepared by melting at high temperature and quick quenching. The glass
density, infrared spectra, optical spectra, ligand field and non-linear optical properties of these perceived glasses
were reported. Through these investigations, the impactive role of barium oxide was prospected. The glass
density was increased by 11 % and bond density was enhanced by 24 % due to barium oxide addition. Further,
infrared spectra revealed the internal glass structure, besides the evolution of structural changes. With barium
oxide addition, there is a conversion from BO3 into BO4 units, accompanied by observed deterioration in nonbridging
oxygens, reflecting the polymerization of glass network. Moreover, the optical spectra of glass present
the nickel transitions within visible and near infrared bands, which promise better performance of glass in
visible and near infrared bands. Using the decomposition method, these optical transitions were detached into
eight transitions of Ni2+ ions in octahedral and tetrahedral coordination. From these transitions, the ligand field
strength (10Dq) was found to mitigate from 7905 to 7485 cm􀀀 1, while the Racah B and C parameters were
increased from (803–843 cm􀀀 1) and (3633–3722 cm􀀀 1), respectively. These behaviors explain the high localization
of electrons within d-orbitals of Ni2+ ions owing to barium oxide addition. In addition, the nephelauxetic
parameters confirmed the increased ionic nature of bonding between Ni2+ ions and their ligands. Furthermore,
the resulting red shift of glass absorption edges affords mitigated Tauc band gaps from 3.41 eV to 3.21 eV. The
addition of barium oxide enhanced the glass refractive index from 1.50 to 1.54. Therefore, the overall optical
non-linear properties of these glasses are enhanced. The current work affords a decent paradigm for establishing
high quality and performance barium borate glass activated by nickel ions