Study of (La,Gd)OCl:Eu3+ phosphors for WLEDs application: photoluminescence and Judd-Ofelt analysis
by S.R. Yashodha; N. Dhananjaya; C. Shivakumara
International Journal of Nanotechnology (IJNT), Vol. 14, No. 9/10/11, 2017

Abstract: A series of layered La1-x-yGdxEuyOCl (x = 0, 0.25, 0.50, 0.75, 0.99; y = 0.01) phosphors were synthesised by the conventional solid-state method at 700°C for 2 h. When x = 0.00 and 0.99, the phosphors were crystallised in the tetragonal structure with space group P4/nmm (No. 129). On increasing Gd3+ ion concentration in Eu3+ activated LaOCl system, GdOCl phase starts appearing. Field emission scanning electron microscopy (FE-SEM) revealed that the particles were agglomerating and form spherical-like morphology. The photoluminescence (PL) spectra reveal that the relative intensity of 5D07F2 transition (619 nm) increases with increase in the Gd3+ ions. This was owing to the property of Gd3+ ions to act as an intermediate sub lattice to facilitate the energy transfer to Eu3+ ions. Intensity parameters and radiative properties such as transition probabilities, radiative lifetime and branching ratio were calculated using the Judd-Ofelt theory. The CIE colour coordinates of Gd0.99Eu0.01OCl phosphor are close to the commercial Y2O3:Eu3+, Y2O2S: Eu3+ and National Television System Committee (NTSC) red phosphor. The results indicate that the quality of red colour production is suitable for white LEDs applications.

Online publication date: Sun, 24-Sep-2017

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