ZnWO₄ :Eu³⁺ phosphor with intense blue LED excitation: photoluminescence and electron density distribution analysis

A high intensity 464 nm excitable ZnWO₄ :Eu³⁺ red-emitting phosphor for warm white lighting applications was prepared using a solid-state reaction method by varying the dopant Eu³⁺ concentration. Crystalline purity and phase identification was confirmed and revealed using powder X-ray diffraction and Rietveld refinement analysis. The surface morphology of Zn_1-x Eu_x WO₄ (x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) was examined using scanning electron microscopy (SEM) techniques. From SEM analysis, the ZnWO₄ :Eu³⁺ phosphor prepared at 1-3% molar Eu³⁺ concentrations exhibited a small pebble-like morphology with a smooth surface. On increasing the molar concentration of Eu³⁺ to >3%, the pebble stone morphology disappeared and a large, smooth irregular polygon-shaped granular-like morphology was obtained. Of the higher mol% Eu³⁺ , the 4% Eu³⁺ -doped ZnWO₄ showed the best photoluminescence properties with high intensity and sharp excitation at 395 and 464 nm, followed by red emission centred at 615 nm with excellent CIE coordinates (x = 0.58 and y = 0.41) in the core red region. Elemental composition and chemical state analysis were carried out for the 4% Eu³⁺ -doped ZnWO₄ phosphor using X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy studies. Based on all the above analyses, the Eu³⁺ -doped ZnWO₄ phosphor was found to be a very efficient red-emitting phosphor under near-UV light as well as under visible light excitation and could be used for white LED and field emissive displays applications.