The concentration effect of Ce3+ ions on the photoluminescence properties of the host sensitized NaMPO4-Ce3+ (M = Mg and Ca) phosphors via solid-state reaction method

Abstract

A series of Ce3+ doped NaMPO4 (M = Mg and Ca) nanophosphors were prepared using the solid-state reaction route, annealed at 900 °C for 4 h (except for NaMgPO4 which was annealed at 780 °C for 4 h). In this study, the concentration effects of Ce3+ ions for x = 0.0, 0.1, 0.5, 1.0, 1.5 and 2.0 mol% were investigated for its structural and photoluminescence (PL) properties. The structural and PL properties of the NaMPO4:xCe3+ compounds were analyzed using different characterization techniques, such as X-Ray diffraction (XRD), Field Emission Scanning Microscopy (FE-SEM), UV–vis diffuse reflection spectroscopy (DRS), Fourier Transform Infrared Spectroscopy (FTIR), PL and International Commission on Illumination (CIE) colour coordinates. XRD results confirm the prepared phosphors were crystallized into monoclinic (NaMgPO4) and orthorhombic (NaCaPO4) structures. SEM results confirm that all prepared samples were formed in the micrometer dimension range, with different sizes and shapes. Energy dispersive X-ray spectroscopy (EDS) spectra confirm the presence of chemical elements in the prepared nanophosphors. The presence of all phosphate (PO43−) and other structural groups were confirmed through FTIR measurements. UV–vis DRS measurements were used to calculate the optical band gap energy values via the Kubelka-Munk function theory. The PLE spectra of the NaMPO4:xCe3+ phosphors were measured in the 200–300 nm range by monitoring their peak at the 385 nm emission wavelength. Using 281 nm excitation wavelength, the PL spectra were measured and a high intensity emission band was found at the 385 nm wavelength (violet colour region). Using PL data of all NaMPO4:xCe3+ ion nanophosphors, the CIE colour coordinates were calculated and were found to lie in the violet colour region of the CIE colour diagram. From all the PL results, it is noticed that enhanced violet colour emissions were observed for all NaMPO4:xCe3+ compounds with increasing Ce3+ ion concentrations, implying that NaMPO4:xCe3+ phosphors are potential candidates for violet colour emitting technologies in display systems.