Preparation and fluorescence properties of La 2 CaB 10 O 19 crystals doped with Pr 3 þ ions A.M. El-Naggar a,1 , N.S. Alzayed a , A. Majchrowski b , L. Jaroszewicz b , M.G. Brik c,n , W. Kuznik d , I.V. Kityk a,e a King Saud University, College of Science, Physics & Astronomy Dept., 11451 Riyadh, Saudi Arabia b Institute of Applied Physics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland c Institute of Physics, University of Tartu, Riia 142, Tartu 51014, Estonia d Department of Physical Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice, Poland e Electrical Engineering Department, Czestochowa University of Technology, Czestochowa, Poland article info Article history: Received 23 May 2011 Received in revised form 22 August 2011 Accepted 23 August 2011 Communicated by V. Fratello Available online 30 August 2011 Keywords: A1. Judd–Ofelt parameters A1. Spectral properties B1. Pr:LCBO abstract High quality La 2 CaB 10 O 19 single crystals doped with Pr 3 þ ions were grown by means of the top seeded solution growth method. The concentration of Pr 3 þ ions in the starting melt was equal to 4 at%, which in consequence gave single crystals containing 2.5 at% of Pr 3 þ ions, due to small distribution coefficient. The absorption and luminescence spectra were recorded in the wavelength range from 200 to 3000 nm at an ambient temperature of 24 1C and analyzed using the Judd–Ofelt theory. With the intensity parameters obtained in the present work, the estimated radiative life time of the 3 P 0 emitting state is 28 ms. Possible applications of this crystal as a luminophore are discussed. & 2011 Elsevier B.V. All rights reserved. 1. Introduction Recently there has been enhanced interest in using Pr-doped oxide matrices as materials for white light emitting diodes (LED) and phosphors. Among different matrices there is particular interest in the borate crystals due to the possibility of convenient introduction of different rare earth ions (Pr 3þ , in particular) into these materials. There are many reports devoted to the studies of the luminescent spectra of Pr 3þ -doped compounds [1,2 and references therein]. The main strategy has been to study the influence of surrounding matrices on the spectral distributions and the lifetimes of the Pr excited emitting states. In the present work we study the influence of Pr 3þ doping on the fluorescence properties of La 2 CaB 10 O 19 bulk single crystals. A peculiar feature of this crystal is its high covalency, which is due to the boron ions and plane BO 3 groups. We report on details of crystal growth of this crystal; spectroscopic measurements were followed by the Judd–Ofelt (JO) analysis of the radiative properties of Pr 3þ ions in the bulk samples. 2. Crystal growth and experimental spectra measurements Single crystals of incongruently melting lanthanum calcium borate La 2 CaB 10 O 19 (LCBO) can be grown only at temperatures lower than the temperature of the peritectic phase transition of this material (about 1050 1C) [3]. The Top Seeded Solution Growth (TSSG) techni- que was used by us to obtain LCBO:Pr single crystals. In our first experiments calcium tetraborate CaB 4 O 7 was used as the solvent. The growth of LCBO crystals from this self-flux suffered from spurious crystallization of LaB 3 O 6 induced by segregation of components during synthesis of the starting material and accumulation of lanthanum enriched melt near the bottom of the crucible. Addition of Li 2 B 4 O 7 , similar to Ref. [4], made the control of the LCBO single crystal growth much easier. The most important improvement of the growth conditions was the elimination of uncontrolled LaB 3 O 6 crystallization. The melt synthesized in a platinum crucible was quickly cooled and formed a uniform glass that did not segregate after placing the crucible in the furnace with consecutive melting. Moreover, the temperature of crystallization was below 1000 1C, much lower than in case of using pure CaB 4 O 7 as the solvent, making control of the LCBO single crystal growth much easier. An equimolar mixture of Li 2 B 4 O 7 and CaB 4 O 7 was used as the solvent. The molar ratio of the flux (LCBO:solvent) was 1:3. The melt contained 4 at% of Pr 3 þ ions substituting for La 3 þ ions. The starting melt was synthesized from high purity compounds: Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jcrysgro Journal of Crystal Growth 0022-0248/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2011.08.037 n Corresponding author. E-mail address: brik@fi.tartu.ee (M.G. Brik). 1 Permanent address: Ain Shams University, Faculty of Science, Physics Dept., Abbassia, 11566 Cairo, Egypt. Journal of Crystal Growth 334 (2011) 122–125