Investigation of a new way of synthesis for Nano crystallites of La2O2S & 1%Ln3+ (Ln = Pr, Eu, Tb, Dy, Er) doped La2O2S and study their structural and optical properties

Abstract

Nano-crystallite Lanthanum oxysulfide (La2O2S), a versatile compound with a wide range of applications, has been synthesized by the Solid State, Hydrothermal, and a novel Furnace Combustion technique. The last one limits the precursors, thus minimizing the resource usage, does not require passing of the H2S, CS2, or any of the hazardous gasses during the reaction and is less time-consuming while providing the maximum yield output. Thus, the novel Furnace Combustion method is marked for potential industrial use. The comparative XRD analysis showed the highest phase purity of the samples created by the Furnace Combustion technique, which was then employed for the synthesis of 1% Ln3+:La2O2S (Ln = Pr, Eu, Tb, Dy, Er) samples. The crystallite size was estimated by the Scherrer equation. The EDAX spectra proved the successful incorporation of doped elements. The samples showed absorption peaks in the UV region attributed to the excitation into 4f5d for Pr3+ and Tb3+, charge-transfer state for Eu3+, host absorption for Dy3+ and 4f levels for Er3+ doped samples. The emission spectra showed 4f - 4f transitions typical for the doped rare-earth ions. The bandgap energies are estimated by the Tauc plot. The 4.95 eV band-gap of pristine La2O2S is significantly dropped by doping. The refractive index values slightly increased by doping with rare-earth ions from 2.00 for the pure sample to ca. 2.20 for the doped samples. © 2020 Elsevier B.V.