Optical characterization and defect-induced behavior in ZnAl1.999Ho0.001O4 spinel: Unraveling novel insights into structure, morphology, and spectroscopic features.

The ZnAl1.999Ho0.001O4 phosphor, prepared by the solid-state method, crystallizes in the cubic spinel structure. Morphology and chemical composition homogeneity were determined via Energy Dispersive X-ray and SEM analysis. The (Eg) optical band gap was evaluated from the UV/vis absorption spectrum, confirming direct transition behavior according to Tauc's law. The Urbach energy (Eu) in the ZnAl1.999Ho0.001O4 spinel was higher than that in the ZnAl2O4 spinel, indicating increased disorder and a higher concentration of defects due to Ho3+ ions. The penetration depth (δ(λ)), optical extinction (k(λ)), and refractive index (n(λ)) were assessed across wavelengths (λ). The room temperature absorption spectrum revealed several peaks corresponding to the 4f-4f transitions of Ho3+ ions.

Study with Analytical Equations of Absorption Spectra Containing Interference Dips in Fluoride Glasses Doped with Cr(3.).

The optical absorption of Cr(3+)-doped fluoride glasses has been investigated. The lowest energy absorption band (4)A2 → (4)T2 shows distinct interference dips due to spin-orbit coupling between (4)T2, (2)E and (2)T1 excited states. The dips were analyzed using an analytical method proposed by Bussière et al. ( J. Phys. Chem. A 2003 , 107 , 1258 ) based on coupled potential energy surfaces. Then a theoretical crystal-field analysis based on the Racah tensor algebraic method was carried on Cr(3+) ions occupying octahedral site symmetry in the fluoride glasses. Satisfactory correlations were obtained between the experimental and calculated energy levels. The fitting of the interference dips also provided a measure of the spin-orbit coupling constant for Cr(3+) in fluoride glasses, intermediate between the theoretical value calculated for a fluoride crystal and the value deduced from Racah parameters.