Luminescence study of Eu 3+ doped Li 6 Y(BO 3 ) 3 phosphor for solid-state lighting Mrunal M. Yawalkar, a G. D. Zade, b K. V. Dabre a and S. J. Dhoble a * ABSTRACT: In this study, Li 6 Y 1–x Eu x (BO 3 ) 3 phosphor was successfully synthesized using a modified solid-state diffusion method. The Eu 3+ ion concentration was varied at 0.05, 0.1, 0.2, 0.5 and 1 mol%. The phosphor was characterized for phase purity, morphology, luminescent properties and molecular transmission at room temperature. The XRD pattern suggests a result closely matching the standard JCPDS file (#80-0843). The emission and excitation spectra were followed to discover the luminescence traits. The excitation spectra indicate that the current phosphor can be efficiently excited at 395 nm and at 466 nm (blue light) to give emission at 595 and 614nm due to the 5 D 0 → 7 F j transition of Eu 3+ ions. Concentration quenching was observed at 0.5 mol% Eu 3+ in the Li 6 Y 1–x Eu x (BO 3 ) 3 host lattice. Strong red emission with CIE chromaticity coordinates of phosphor is x = 0.63 and y =0.36 achieved with dominant red emission at 614nm the 5 D 0 → 7 F 2 electric dipole transition of Eu 3+ ions. The novel Li 6 Y 1–x Eu x (BO 3 ) 3 phosphor may be a suitable red-emitting component for solid-state lighting using double-excited wavelengths, i.e. near-UV at 395nm and blue light at 466nm. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: solid-state diffusion; phosphor; solid-state lighting; luminescence; Li 6 Y(BO 3 ) 3 Introduction Although compact fluorescent lamps have gained popularity among consumers, the presence of the toxic metal mercury in them has outweighed their advantages, and people are switching to a more efficient mode of lighting, the light-emitting diodes (LEDs) (1). The color rendition of these eco-friendly LEDs depends on the rare earth (RE) element incorporated within them. The cur- rent fabrication of white LEDs includes a blue-emitting InGaN chip and a yellow-emitting phosphor Y 3 Al 5 O 12 :Ce 3+ (YAG) (2). However, this is reported to exhibit a poor color rendering index (CRI) of 80 with a high color temperature due to the inadequacy of red emission. Therefore, it has become necessary to discover new red phosphors that can be successfully excited near 400 nm (3–5). Scientists are showing keen interest in using Eu 3+ RE ions to ob- tain a red-emitting phosphor. Eu 3+ ions reveal the lowest excited level 5 D 0 of the 4f 6 configuration, which is located below the 4f 6 5d configuration and principally displays very sharp red emis- sion lines around 610–618 nm due to 5 D 0 → 7 F 2 transition (6). Most of the red-emitting phosphors efficiently excited around 393 nm originate from 7 F 0 → 5 L 6 transitions, which are parity forbidden and exist as a sharp peak. The varying crystal chemistry of borates imparts upon them attractive optical properties, a large electronic band gap, environmental and chemical stability and mechanical strength (7). This has motivated researchers to synthesize numer- ous borate structures for utilization in high-technology areas. Double orthoborate Li 6 RE(BO 3 ) 3 (RE = Y or lanthanides) crystals are considered to be good materials for laser applications. When activated with RE ions these materials can also be used as scintilla- tion detectors for thermal neutrons and gamma photons. Li 6 RE (BO 3 ) 3 compounds are known to crystallize in the monoclinic sys- tem with space group P2 1 /c, Z = 4 and have an isostructural nature, as a result of which the host lattice can be isomorphically substituted (8). The structure is made up of edge-sharing REO 8 polyhedrals that form chains along the C-axis, which brings about one-dimensional energy transfer between RE 3+ ions. The RE ions doped in these materials determine the materials’ spectroscopic properties as well as their practical uses. Trivalent REs, especially europium- and cerium-doped lithium–yttrium–orthoborate, are known to have good spectroscopic characteristics such as a strong light output and short decay time (9,10). Here, we report the detailed study of an Eu-doped Li 6 Y(BO 3 ) 3 phosphor synthesized using a modified solid-state diffusion method. It was characterized for phase purity, morphology, lumi- nescent properties and molecular transmission at room temperature. Experimental Synthesis The Li 6 Y 1-x Eu x (BO 3 ) 3 phosphor was synthesized by a modified solid-state reaction route using the following chemical reaction: 3Li 2 CO 3 þ 1 –x ð Þ=2Y 2 O 3 þ 3H 3 BO 3 þx=2 Eu 2 O 3 → Li 6 Y 1-x Eu x BO 3 ð Þ 3 þ 9=2H 2 O ↑ þ 3CO 2 ↑ Here the value x in the prepared phosphor is the molar replace- ment of Y 3+ by Eu 3+ The mole fractions of Eu 3+ used were 0.05, 0.1, * Correspondence to: S. J. Dhoble, Department of Physics, R.T.M. Nagpur Univer- sity, Nagpur - 440033, India. E-mail: sjdhoble@rediffmail.com a Department of Physics, R.T.M. Nagpur University, Nagpur - 440033, India b Department of Physics J. N. Arts, Commerce & Science College, Wadi, Nagpur - 440023, India Luminescence 2015 Copyright © 2015 John Wiley & Sons, Ltd. Short communication Received: 4 May 2015, Revised: 13 July 2015, Accepted: 15 July 2015 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI 10.1002/bio.3006