Influence of SO₄²⁻ anionic group substitution on the enhanced photoluminescence behaviour of red emitting CaMoO₄:Eu³⁺ phosphor

CaMoO₄:xEu³⁺(x = 0.5, 1.0, 1.5, 2.0, and 2.5) powder phosphors incorporating SO₄²⁻ anions were synthesized at high temperature using the solid-state reaction technique. The structural, morphological and optical properties of these phosphors were analysed using X-ray diffraction (XRD), field emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and optical spectroscopy. The XRD results indicate that the incorporation of SO₄²⁻ anions and Eu³⁺ dopant ions did not affect the crystal structure of the CaMoO₄, but largely influenced the luminescence properties of the CaMoO₄–SO₄:Eu³⁺ phosphors.The optical properties of our materials were examined using the UV–vis absorption spectroscopy. The absorption edges of the phosphors with different concentrations of Eu³⁺ were less than the band gap energy of the CaMoO₄ and their values ranged from 3.30 to 4.75 eV. The intensity of the red photoluminescence (PL) from CaMoO₄:Eu³⁺ phosphors was enhanced considerably upon incorporation of SO₄²⁻ anions, suggesting that SO₄²⁻ acted to capture primary excitation energy and transfer it non-radiatively to Eu³⁺ ions. In addition, the incorporation of SO₄²⁻ ions also improved the fluorescence decay life-time values of the CaMoO₄:xEu³⁺ phosphors significantly. Tunable emission was observed when the Eu³⁺ concentration was varied. Our PL results indicated that the CaMoO₄–SO₄:Eu³⁺ phosphor exhibited the highest red emission intensity compared to CaMoO₄: Eu³⁺ phosphors, suggesting that CaMoO₄–SO₄:Eu³⁺ could be a promising red component material for potential application in white light-emitting diode devices.