Synthesis and luminescence property of Li 2 BaP 2 O 7 : Ln 3 þ (Ln ¼ Eu, Sm) phosphors J.A. Wani a , N.S. Dhoble b , N.S. Kokode c , B. Deva Prasad Raju d , S.J. Dhoble a,n a Department of Physics, R.T.M. Nagpur University, Nagpur 440033, India b Department of Chemistry, Sevadal Mahila Mahavidhyalaya, Nagpur 440009, India c BCUD Gondwana University, Gadchiroli, India d Department of Future studies, Sri Venkateswara University, Tirupati 517502, India article info Article history: Received 19 April 2013 Received in revised form 29 September 2013 Accepted 3 October 2013 Available online 22 October 2013 Keywords: Lithium barium diphosphate Luminescence Phosphors Solid state lighting abstract Phosphate compounds as host materials are always a good choice for lanthanides to exhibit luminescence. The novel phosphors of Li 2 BaP 2 O 7 activated with the trivalent Eu 3þ and Sm 3þ ions were synthesized by high temperature solid state reaction. In characterization, crystallization, morphology and luminescent properties of lithium barium diphosphate were investigated. The excitation and emission spectra were recorded to study the luminescence properties. The as prepared powders of Eu 3þ and Sm 3þ ions doped Li 2 BaP 2 O 7 emit reddish orange light, corresponding to 5 D 0 - 7 F 1 (595 nm) and 4 G 5/2 - 6 H 7/2 (599 nm) transitions, respectively. The study is novel as no such luminescence data are available for this compound. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Solid state lighting based on the inorganic LEDs has now become the topic of extreme research interest for researchers and scientists all over the world for the last few decades owing to its tremendous advantages over conventional lighting devices. This system of illumination is predicted to take over as the future lighting technology to illuminate the whole world. There are various ways to develop white light using LEDs, three of which are given below. The first approach is to employ individual LEDs with red, green and blue colors, together in single light bulb, to yield white light. The second way is to use ultraviolet LEDs, which illuminate a red, green and blue phosphor. These phosphor materials convert the high energy UV light from the LED chip, down to lower energy wavelengths of red, green and blue light. The total light is combined to produce white light. The third way is to use a blue LED to illuminate a yellow phosphor. Among the three, the second one is mostly adopted to develop white light because its color rendering index (CRI) is considered better than rest of them [1–3]. As host materials, phosphates have proven their place in phosphor industry due to their excellent thermal and chemical stability. In fact numbers of phosphates phosphors e.g., LiSrPO 4 :Eu 2 þ .Tb 3 þ , (Sr, Ca) 2 P 2 O 7 : Eu 2 þ ,Mn 2 þ , Ca 19 Zn 2 (PO 4 ) 14 :E 3 þ and MMgP 2 O 7 :Eu 3 þ (M¼ Ca, Ba, Sr) have shown that they can be effectively excited in the NUV-region to generate white light. In this work photoluminescence of Eu 3 þ and Sm 3 þ doped Li 2 BaP 2 O 7 phosphors are reported. To the best of our knowledge, no one has reported Eu 3 þ and Sm 3 þ doped photoluminescence results on this compound. Therefore, we might say that these results are first time reported. These phosphors were synthesized by high tem- perature solid state diffusion method. The spectroscopic results indicate that these phosphors might prove an important compo- nent in the pc-white light using LEDs. The earlier studies on this compound were focused to look into the electrical property such as ionic conductivity. It has been reported that structure of Li 2 BaP 2 O 7 is isostructural with Co 2 BaSi 2 O7 and crystallizes in the monoclinic system with space group C2/c. The crystal structure details of Li 2 BaP 2 O 7 can be found elsewhere [4]. 2. Experimental The starting materials Li 2 CO 3 (A.R), BaCO 3 (A.R), (NH 4 )H 2 PO 4 (A.R), Eu 2 O 3 (99.99%) and Sm 2 O 3 (99.99%) were used. The Li 2 BaP 2 O 7 :Ln 3þ (Ln¼ Eu and Sm) phosphors were prepared by the high temperature solid state reaction. The reactants were mixed stoichiometrically. The concentrations of Eu 2 O 3 used were 0.0005, 0.001, 0.003, 0.005, 0.01 mole and that of Sm 2 O 3 were 0.001, 0.003, 0.005, 0.01 and 0.02 mole. The starting materials were ground for more than half an hour, using agate mortar and pestle. Finally, the ground mixtures were fired at 750 1C for 15 h followed by slow cooling to room temperature. The samples at room temperature were taken out and further pulverized Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence 0022-2313/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jlumin.2013.10.007 n Corresponding author. E-mail address: sjdhoble@rediffmail.com (S.J. Dhoble). Journal of Luminescence 147 (2014) 223–228