Impact of sunlight on the optical properties and ligand field parameters of nickel borosilicate glasses

Abstract In this paper, the impact of sunlight on stability and ligand field parameters of borosilicate glasses doped with NiO synthesized via melt quenching approach is reported. XRD analysis confirms the absence of any crystalline nature for the glass matrices. The average density (D), molar volume (Vm) and microstructural parameters were investigated. Optical features of these glasses were determined by measuring their absorption spectra in the visible-near infrared region. The absorption spectra of Ni2+ show four fundamental absorption bands that are associated with the wavenumbers ν1, ν2, ν3 and ν4 which attributed to; allowed electronic transitions ν1: 3A2g(F) → 3T2g(F), ν2: 3A2g(F) → 3T1g(F), ν3: 3A2g(F) → 3T1g(P) and forbidden transition ν4: 3A2g(F) → 1Eg(D). These absorption bands were availed to obtain Racah parameter (B) and ligand field splitting (Δ0). It was found that the average density and molar volume were decreased with further NiO doping. The impact of NiO doping on the glass color, B and Δ0 was determined. Additionally, the influence of sunlight on the glass % degradation, B and Δ0 was determined. All the investigated glass samples are stable under sunlight irradiation meanwhile stability has decreased with NiO increment. The glass sample with 1 NiO content has the lowest degradation % under sunlight and so is the most stable one; no change has been detected in the ligand field parameters. This study paves the way for understanding the impact of sunlight (solarization) on the stability, optical properties and ligand field parameters of glasses used for solar cells and smart widows.