Abstract
A series of Ce3+ doped ABPO4 (A = Na, B = Mg, Ca, Sr, and Ba) nanophosphors were prepared using the solid-state reaction route, annealed at 900°C for 4 hours (except for NaMgPO4 which was annealed at 7800C for 4 hours). 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 properties. The structural and photoluminescence properties of the ABPO4:xCe3+ compounds were analysed using different characterization techniques, such as the X-Ray Diffraction, the Field Emission Scanning Microscopy, UV-vis DRS Spectroscopy, Fourier Transform Infrared Spectroscopy, Photoluminescence and CIE colour coordinates. XRD results confirm the prepared phosphors were crystallized into monoclinic (NaMgPO4 and NaSrPO4) and orthorhombic (NaCaPO4 and NaBaPO4) structures. These structures compare favourably with the standard structures stored in the JCPDS database. SEM results confirm that all prepared samples were formed in the micrometre dimension range, with different sizes and shapes. EDS spectra confirm the presence of chemical elements in the prepared nanophosphors. The presence of all phosphate (PO43-) and other structural groups was confirmed through FTIR measurements. UV-vis DRS measurements were used to calculate the optical band gap energy values via the Kubelka-Munk function theory. From the Tauc plots, it is observed that the band gap energy values were found to decrease with increases in Ce3+ ion concentrations. The PLE spectra of the ABPO4:xCe3+ phosphors were measured in the range 200 to 300 nm range by monitoring their peak at 385 nm emission wavelength. The PLE spectra confirm that a high intensity excitation band was found at 281 nm wavelength. Using the excitation wavelength, the PL spectra were measured in the range from 300 to 400 nm, and from the PL spectra, it is noticed that a high intensity emission band was found at 385 nm wavelength (violet colour region). Upon increasing the Ce3+ ion concentration for all ABPO4 compounds, the emission intensity increased up to a critical concentration of Ce3+ ion, thereafter it decreased due to quenching effects. Using PL data of all ABPO4:Ce3+ 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 ABPO4:xCe3+ compounds with increasing Ce3+ ion concentrations, implying that ABPO4:xCe3+ phosphors are potential candidates for violet colour emitting technologies in display systems.
M.Sc. (Physics)