Studies of defects in YVO₄:Pb²⁺, Eu³⁺ red phosphor material

Abstract

Doubly doped YVO₄:Pb²⁺, Eu3⁺ red phosphor materials with fixed Eu³⁺ concentration (5 mol%) and varying Pb²⁺ concentration were prepared via a self-propagating (combustion) synthesis. This consisted of bringing a saturated aqueous solution of the desired metal salts and a suitable organic fuel to the boil, until the mixture ignited and a self-sustaining and rather fast combustion reaction initiated, resulting in dry, amorphous or usually crystalline fine particles of the desired material. The formation of crystalline vanadates was confirmed by X-ray diffraction. A strong emission line at 619 nm due to the ⁵D₀ → ⁷F₂ transition in the red region was observed. Defects, created by gamma radiation, were studied by means of photoluminescence, thermally stimulated luminescence (TSL) and electron spin resonance. Photoluminescence studies display considerable reduction in emission intensity which appears to arise due to the formation of defect centres after irradiation. The defect centres formed in the present system are tentatively assigned to F⁺ centres and step annealing measurements suggest a connection between these centres and the TSL glow peak.