Enhanced and Long-Lived Near-Infrared Luminescence of Er 3+ Ions in Lead Borate Glass-Ceramics Containing PbWO 4 Nanocrystals Wojciech A. Pisarski, ‡,† Joanna Pisarska, ‡ Izabela Czopek, ‡ Tomasz Goryczka, § Radoslaw Lisiecki, ¶ and Witold Ryba-Romanowski ¶ ‡ Institute of Chemistry, University of Silesia, Szkolna 9, 40-007 Katowice, Poland § Institute of Materials Science, University of Silesia, Bankowa 12, 40-007 Katowice, Poland ¶ Polish Academy of Sciences, Institute of Low Temperature and Structure Research, Ok olna 2, 50-422 Wroclaw, Poland Lead tungstate PbWO 4 nanocrystals in transparent lead borate glass-ceramics containing Er 3+ ions were fabricated. Lumines- cence spectra at about 1530 nm due to main 4 I 13/2 – 4 I 15/2 laser transition of Er 3+ ions were examined for glass samples before and after heat treatment. Near-infrared luminescence of Er 3+ ions in glass-ceramics is enhanced and long-lived in comparison to precursor glasses. It suggests that the Er 3+ ions are par- tially incorporated into PbWO 4 crystalline phase. I. Introduction T HE PbWO 4 single crystals belonging to the ABO 4 -type tetragonal family 1 are known from their scintillations. 2 They are used for construction of electromagnetic calorime- ters, where they are main elements of detectors system PHOS (Photon Spectrometer) in ALICE experiment program. 3 The advantage of the PbWO 4 crystals is their high density and transparency. Moreover, they reveal a possibility of scintilla- tion light in blue range and high detection efficiency of the gamma quantum radiation. The PbWO 4 matrix promotes doping lanthanides. 4–6 Trivalent lanthanide ions deal lead ions Pb 2+ and tungsten ions W 6+ in the PbWO 4 crystal, which caused numerous structural defects. 6 Increased interest of these materials in last year’s and pres- ent numerous structure defects in PbWO 4 single crystals caused searching for new technological solutions for their receipt. Previously mentioned limitations have led to obtain the PbWO 4 crystals or powders in nanometric scale. Obtained nanocrystalline materials by chemical wet method assisted by microwave irradiation 7 can emit a blue light. Likewise, the PbWO 4 nanocrystals can be received by sono- chemical method 8 and nanopowders activated by erbium and ytterbium ions by hydrothermal method at different pH values. 9 The PbWO 4 nanocrystals were synthesized via the precipitation reaction of Na 2 WO 4 and Pb(NO 3 ) 2 in aqueous solution, where phase transformation of lead tungstate at normal temperature from tetragonal to monoclinic structure is possible. 10 An alternative way for synthesis of PbWO 4 nanocrystals can be the controlled crystallization of the glasses containing appropriate concentration of lead and tungsten oxide. The heat treatment of these glasses, carried out under specific conditions of time and annealing temperature, can cause transformation from the glassy state to transparent glass- ceramics with the PbWO 4 crystalline phase. To achieve that, the lead borate glassy matrix is proposed. Our previous research has shown that oxyhalide lead borate glasses doped with Er 3+ 11 are promising materials emitting in NIR range (so called third telecommunication window). An effective way to obtain nanocrystals distributed in amorphous glassy matrix is to use heat treatment process, which provides transition from glass state to glass-ceramic system. The spectroscopic consequence of this structural transformation is narrowing of luminescence lines and elon- gation of luminescence decays, when the optically active ions are incorporated into crystalline phase. These effects were also observed for Eu 3+ ions incorporated into YPO 4 nano- crystals belonging to the same ABO 4 -type tetragonal fam- ily. 12 Till nowadays lead tungstate PbWO 4 nanocrystals were not prepared by controlled heat treatment of precursor glasses, as far as we know. For that reason, we proposed fabrication of erbium-doped glass-ceramics containing PbWO 4 phase by heat treatment of precursor lead borate glasses. Alternatively, the PbWO 4 crystals in lead borate sys- tem can be formed during laser irradiation, which was pro- posed by M. Rada et al. 13 It also indicates that this new class of glass-ceramic materials is promising for structural and optical investigations. II. Experimental Procedure Multicomponent oxyhalide lead borate-based glasses were prepared. The nominal chemical composition of lead borate glass was as follows (in wt%): 9PbX 2 –72PbO–18B 2 O 3 – 6Al 2 O 3 –3WO 3 –1Er 2 O 3 , where X denotes Cl or Br. Anhydrous oxides and lead halide PbX 2 [99.99% purity; Sigma-Aldrich, St. Louis, MO, USA] were used as starting materials. To prepare samples, the appropriate amounts of all components were mixed homogeneously together and heated in an atmosphere of dry argon. The mixed reagents were melted at 850°C for 2 h in Pt crucibles, then poured into preheated copper molds and annealed below the glass transition temperature. After this procedure, the samples were slowly cooled to the room temperature. The glasses were characterized by a (Perkin-Elmer DSC-7, Waltham, MA 02451, USA) differential scanning calorimeter (DSC). The DSC curves were acquired with a heating rate of 10°/ min. Next, the glass samples were heat-treated at 450°C for 10 h to obtain transparent glass-ceramics. The X-ray diffrac- tion patterns were carried out using INEL diffractometer with CuKa radiation (INEL CPS-120, Artenay, France). B. Deva Prasad Raju—contributing editor Manuscript No. 32819. Received February 28, 2013; approved March 22, 2013. † Author to whom correspondence should be addressed. e-mail: wojciech.pisarski@ us.edu.pl 1685 J. Am. Ceram. Soc., 96 [6] 1685–1687 (2013) DOI: 10.1111/jace.12340 © 2013 The American Ceramic Society J ournal Rapid Communication