Host sensitized tunable luminescence of single phase white light emitting Ca2Sb2O7:Eu3+ phosphors
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A series of Eu3+ doped calcium antimonate (Ca(2−x)Sb2O7:xEu3+, x = 0, 0.05, 0.07, 0.09, 0.1, 0.2 mol%) phosphors were synthesized via high-temperature solid-state reaction method. The structural and optical characterizations of the prepared samples were done using X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet–visible-near infrared (UV–Vis-NIR) absorption spectroscopy, photoluminescence excitation and emission spectra, and luminescence decay measurements of the phosphors. X-ray diffraction spectrum confirmed the phase purity and orthorhombic weberite structure of the samples. Excitation spectrum suggests that the prepared phosphors can be effectively excited by UV (300 nm/330 nm), NUV (393 nm) and blue (464 nm) light-emitting diodes (LEDs). Under 330 nm ultraviolet excitation, calcium antimonate host exhibits a broad blue emission band, while Eu3+ doped Ca2Sb2O7 samples exhibit blue emission band of host and characteristic emission bands of Eu3+ ions resulting in a tunable near white light emission. The energy transfer mechanism from host to activator ions is explained. Under rare earth excitations of 393 nm and 464 nm, the samples exhibit strong reddish-orange emission. Concentration dependence of emission intensity was studied and the critical energy transfer distance of Eu3+ ions in Ca(2−x)Sb2O7:xEu3+ phosphors was calculated. The concentration quenching of emission intensity was found to be due to dipole–dipole interaction. The Commission International de L’Eclairage coordinates (CIE), color purity, correlated color temperature (CCT), and luminescence lifetimes of the samples were also evaluated. The results indicate that through careful engineering of the dopant concentration and also by changing the excitation wavelength, emission color can be tuned from red to white which envisages the prepared phosphors as a promising candidate in solid-state lighting and display fields.
The author Anns George is thankful to University Grants Commission, Govt. of India for the award of CSIR-UGC Junior Research fellowship. The authors Subash Gopi and Sreeja E are thankful to University Grants Commission, Govt. of India for the award of UGC BSR fellowship. The authors acknowledge the Department of Science and Technology, Govt. of India for the financial assistance through DST-PURSE (SR/S9/Z-23/2010/22 (C,G)) program. The authors acknowledge MoU-DAE-BRNS Project (No. 2009/34/36/BRNS/3174), Department of Physics, S.V. University, Tirupati, India for extending the experimental facility for decay measurements.
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