Title: Study of (La,Gd)OCl:Eu³⁺ phosphors for WLEDs application: photoluminescence and Judd-Ofelt analysis

Authors: S.R. Yashodha; N. Dhananjaya; C. Shivakumara

Addresses: Department of Physics, Sai Vidya Institute of Technology, Bangalore – 560 064, India ' Department of Physics, B.M.S. Institute of Technology and Management, Bangalore – 560 064, India ' Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore – 560012, India

Abstract: A series of layered La_1-x-yGd_xEu_yOCl (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 ⁵D₀ → ⁷F₂ 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 Gd_0.99Eu_0.01OCl 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.

Keywords: inorganic compounds; powder diffraction; rare earths; luminescence; Judd-Ofelt.

DOI: 10.1504/IJNT.2017.086765

International Journal of Nanotechnology, 2017 Vol.14 No.9/10/11, pp.801 - 815

Published online: 24 Sep 2017 *

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