Photoluminescence study of combustion synthesis of Sm3+ and Dy3+ activated MgAl2O4 phosphor for w-LEDs
摘要
A series of Sm3+ and Dy3+ activated MgAl₂O₄ phosphors was effectively prepared through combustion method. Structural and optical properties are investigated by using XRD, FTIR, and PL analysis. XRD (X-ray diffraction pattern) of prepared sample exhibits that all samples produced are in single phased and match with standard JCPDS no 01-072-1331. The XRD pattern indicates cubic structure. The FTIR spectra of MgAl₂O₄ phosphor show Al–O, Mg–O, and Mg–O–Al stretching vibrations, confirming the MgAl₂O₄ structure. The luminescence properties are comprehensively investigated by recording the photoluminescence (PL) excitation and emission spectra. The MgAl₂O₄:Sm3+ phosphors show the strong absorption range in 340–420 nm, which is well suited for the application in LEDs. Under the excitation at 403 nm, the MgAl₂O₄:Sm3+ phosphor emits yellow, orange and red emission along the CIE chromaticity coordinates found at 565 nm (0.408, 0.589), 603 nm (0.640, 0.359) and 650 nm (0.725, 0.274). The optimal doping concentration of Sm3⁺ in MgAl₂O₄ was found to be 1 mol%. The photoluminescence (PL) emission spectra of MgAl₂O₄ doped with Dy3+ ions exhibit two distinct emission peaks located at 483 nm (4F9/2→6H15/2) and 577 nm (4F9/2→6H13/2). Among these, the 483 nm emission is more intense, indicating a dominant blue emission in the Dy3+-doped MgAl₂O₄ phosphor. The measured chromaticity coordinates of MgAl2O4: Dy3+ phosphor for the emission line at 483 nm and 577 nm were (0.078, 0.170) and (0.492, 0.506), which fall in blue and yellow regions of the CIE diagram, respectively. The concentration mechanism has been studied, and it is caused by dipole–dipole interactions for both Sm3+ and Dy3+ ions. The results demonstrate MgAl₂O₄:RE3+ (RE3+ = Sm3+, Dy3+) phosphors have the potential to function as red–orange phosphors for white LEDs.