Role of nickel ion coordination on spectroscopic properties of multi-component CaF2–Bi2O3–P2O5–B2O3 glass-ceramics

• CaF2–Bi2O3–P2O5–B2O3 glasses doped with NiO were crystallized by heat treatment.
• Glass ceramic samples were characterized by XRD, SEM, EDS and DTA data.
• Optical absorption studies indicated that nickel ions do exist in both tetrahedral and octahedral sites.
• FTIR and Raman spectra indicated the growing degree of disorder in the ceramic network beyond 1.5 mol% of NiO.
• Glass-ceramic doped beyond 1.5 mol% of NiO can be expected as an amplification medium for broadband optical amplifiers.

Multi-component CaF2–Bi2O3–P2O5–B2O3 glasses doped with different concentrations of NiO were crystallized through heat treatment. The prepared glass ceramic samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) as well as conventional spectroscopic studies viz., optical absorption, Fourier transform infrared (FTIR) and Raman. The XRD and SEM studies have indicated that the samples contain well defined and randomly distributed grains of different crystalline phases. The optical absorption studies together with FTIR and Raman measurements indicated the gradual transformation of nickel ions from tetrahedral sites to octahedral sites (lasing sites) as the concentration of NiO is increased beyond 1.5 mol%. All these investigations have indicated that the growing degree of disorder in the glass ceramic network at higher concentrations of NiO. Glass ceramics doped with NiO beyond 1.5 mol% appear to be suitable for getting laser emission due to 3T2(F) → 3A2(F) transition in NIR region. These glass-ceramics can be expected as an amplification medium for tunable lasers and broadband optical amplifiers for wavelength division multiplexing transmission system.