ZnWO<sub>4</sub>:Eu<sup>3+</sup> phosphor with intense blue LED excitation: photoluminescence and electron density distribution analysis
D. Sivaganesh, S. Saravanakumar, S. Saravanakumar, V. Sivakumar, S. Sasikumar, S. Sasikumar, J. Nandhagopal, Rajajeyaganthan Ramanathan
Abstract
Abstract A high intensity 464 nm excitable ZnWO 4 :Eu 3+ red‐emitting phosphor for warm white lighting applications was prepared using a solid‐state reaction method by varying the dopant Eu 3+ 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 WO 4 (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 ZnWO 4 :Eu 3+ phosphor prepared at 1–3% molar Eu 3+ concentrations exhibited a small pebble‐like morphology with a smooth surface. On increasing the molar concentration of Eu 3+ to >3%, the pebble stone morphology disappeared and a large, smooth irregular polygon‐shaped granular‐like morphology was obtained. Of the higher mol% Eu 3+ , the 4% Eu 3+ ‐doped ZnWO 4 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% Eu 3+ ‐doped ZnWO 4 phosphor using X‐ray photoelectron spectroscopy and energy dispersive X‐ray spectroscopy studies. Based on all the above analyses, the Eu 3+ ‐doped ZnWO 4 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.