Vol. 39, Issue 2, pp. 375-382 (2009)

Abstract

Scheelite-type LiEuW₂O₈ (LEW) phosphors with the optical function of color conversion  from near-UV to red were prepared by sol–gel method using a lithium acetate dehydrate, europium(III) nitrate pentahydrate, and tungsten(VI) chloride as starting materials. Viscous mixing sol was prefired at 300 °C for 120 min in air and then white powder precursor was finally annealed at 500–800 °C for 240 min in Ar. From an X-ray diffraction analysis, all the samples are isostructural and belong to the tetragonal system of scheelite-type. The main emission peak is ⁵D₀ → ⁷F₂ transitions of Eu³⁺ at 615 nm, other transitions from the ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₃ and ⁵D₀ → ⁷F₄ located at 570–700 nm range are weak. The characteristic emission of WO₄^–2 in LEW is quenched absolutely and only red-light emission of Eu³⁺ appears. Crystallinity, surface properties and red-emission by near-ultraviolet (395 nm) were improved by high-temperature annealing.