Luminescence improvement in Pr 3+ and Gd 3+ activated Sr 2 Mg(BO 3 ) 2 inorganic phosphor A.B. Gawande a, **, R.P. Sonekar a, *, S.K. Omanwar b a Department of Physics, SGB Amravati University, Amravati, Maharashtra, India b Department of Physics, G.S. College, Khamgaon, Buldhana, Maharashtra, India A R T I C L E I N F O Article history: Received 1 March 2014 Received in revised form 28 July 2014 Accepted 30 August 2014 Available online 2 September 2014 Keywords: A. Inorganic compounds B. Luminescence D. Phosphors A B S T R A C T The photoluminescence properties of (Sr 1x Pr x ) 2 Mg(BO 3 ) 2 ; (Sr 12x Pr x M x ) 2 Mg(BO 3 ) 2, (M = Li, Na, K); (Sr 1x Gd x ) 2 Mg(BO 3 ) 2 ; (Sr 12x Gd x M x ) 2 Mg(BO 3 ) 2 , (M = Li, Na, K) and (Sr 14x Pr x Gd x Na 2x ) 2 Mg(BO 3 ) 2 inorganic phosphors prepared by solution combustion synthesis technique are discussed. The structure of the prepared phosphor characterized using Thermogravimetric–differential thermal analysis, X-ray diffraction and fourier transform-infrared. Scanning electron microscopy images of the prepared materials show irregular grains with agglomerate phenomena. Photoluminescence properties were studied at room temperature. Optimum concentration and critical transfer distance of the synthesized phosphors were determined. ã 2014 Elsevier Ltd. All rights reserved. 1. Introduction The range between 200–280 nm is known to be germicidal (lethal to microorganisms). This range of wavelengths is also known as the germicidal spectrum. The UV-C spectrum (200–280 nm) is the most lethal wavelength for microorganisms, because it disrupts the chemical bonds between the atoms which, in biological terms, results in a “dead” microorganism. The germicidal spectrum is used to destroy bacteria, mold, viruses and other biological contaminants in the air, in liquids, or on surfaces. UV-C’s effectiveness is directly related to intensity and exposure time. UV-C light, which continues to be a reliable means of disinfection, involves exposing contaminated water to radiation from UV light. Caiut et al. [1], reported UVC emitting nano-crystalline lanthanum orthophosphate LaPO 4 :Pr 2 % and calcium pyrophosphate Ca 2 P 2 O 7 :Pr 2 %,Na 2 % synthesized by the controlled spray pyrolysis methodology. Recently, several Pr 3+ doped phosphors are reported by Meltzer et al. [2] which includes LaPO 4 :Pr, YPO 4 :Pr, YAlO 3 :Pr, Pr(PO 3 ) 3 , etc., as UV emitting scintillators and characterized their scintillator properties. Accord- ing to their conclusions, these materials would facilitate the detection of ionizing radiation in open areas, even during the daylight hours, and could be used to support large area surveys that monitor for the presence of ionization radiation due, for example, to system leaks or transfer contamination. These materials can be used in the form of powders, thin films or paints for radiation detection. The emission of Pr 3+ is diverse. It depends greatly on the nature of the inorganic matrix in which it has been introduced. It is well known that SrTiO 3 :Pr 3+ is a red phosphor for field emission displays (FEDs). Jeong et al. [3] have reported BaTiO 3 :Pr 3+ phosphor having similar perovskite type crystal structure, optical characteristics and fundamental absorption edges (3.2 eV) as SrTiO 3 :Pr 3+ by solvothermal method. Ultraviolet B (UVB) has become the phototherapy treatment of choice for psoriasis, vitiligo, atopic dermatitis (eczema) and other photo-responsive skin disorders. UVB can be divided as narrow-band UVB and broadband UVB. Broadband UVB radiation has been used for the treatment of psoriasis for decades [4]. Various investigations imply that the most favorable range for the effective UVB treatment of psoriasis is in the long-wave part of the UVB spectrum i.e., between 305 and 315 nm [5,6]. A narrow UVB source emitting at about 311 nm was made available around 1988 [7]. This has revolutionized the UVB phototherapy [8]. LaB 3 O 6 :Gd, Bi is a phosphor used in commercial narrow UVB phototherapy lamps. In our previous work we have reported the luminescence in Gd 3+ activated YBO 3 phosphor and also investigated the energy transfer from Bi 3+ and Pr 3+ to Gd 3+ . Sonekar et al. [9] have reported borate host phosphor materials LaBO 3 , LaB 3 O 6 , LaB 5 O 9 , YBO 3 doped with Gd 3+ ions for UV lamps. Host lattices which are easily synthesizable and structurally viable for doping at multiple cationic sites present in the lattice are of recent interest. The borate atom has two types of hybridized * Corresponding author. Tel.: +91 9422883314. ** Corresponding author. Tel.: +91 9404689773. E-mail addresses: gawandeab@gmail.com (A.B. Gawande), sonekar_rp@yahoo.com (R.P. Sonekar). http://dx.doi.org/10.1016/j.materresbull.2014.08.053 0025-5408/ ã 2014 Elsevier Ltd. All rights reserved. Materials Research Bulletin 60 (2014) e285–e291 Contents lists available at ScienceDirect Materials Research Bulletin journal homepage: www.else vie r.com/locat e/mat resbu