Judd−Ofelt analysis, electronic and elastic properties from ab-initio study and photo-cathodoluminescence studies of Eu3+ activated CdWO4 nanophosphors

Abstract

In the present work, CdWO4:Eu3+ (1–9 mol%) nanophosphors were synthesized by hydrothermal method. X-ray diffraction studies show that all compounds crystallized in monoclinic system with a wolframite structure of space group P2/c (No.13). The surface morphology studies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed nano-rod like structures with size of the particle is approximately 40 nm. The functional group analysis were carried out by Fourier transform Infrared spectroscopy (FT-IR). The first principle quantum mechanical calculations based on density functional theory are performed using Crystal17 code to calculate the electronic and elastic properties. Luminescent characteristics, PL emission spectra show characteristics charge transfer (CT) band of CdWO4 and the emission bands corresponding to typical f-f transitions of Eu3+. The possible mechanism of concentration quenching effect is determined to be multipole-multipole interaction. The Eu3+ activated CdWO4 show red emission peak at 614 nm due to Eu3+ ion corresponding to 5D0 → 7F2 transition upon 295 nm excitation. The 5D0 → 7F1 (590 nm) magnetic dipole transition are less strong intense than 5D0 → 7F2 (614 nm) electric dipole transition. Judd–Ofelt parameters (Ω2 and Ω4), transition probabilities (AT), luminescence lifetime branching ratio are calculated first time for CdWO4 system. The value of is found greater than confirms the covalency between the metal and ligands indicates asymmetric environment around activator. Low voltage cathodoluminescent (CL) measurement were performed for Eu3+ activated CdWO4. The color chromaticity coordinates (CIE) values are estimated from the emission spectra and discussed in detail.