Rapid synthesis and enhancement in down conversion emission properties of BaAl2O4:Eu2+,RE3+ (RE3+=Y, Pr) nanophosphors

[EN] BaAl2O4:Eu2+,RE3+ (RE3+=Y, Pr) down conversion nanophosphors were prepared at 600 °C by a rapid gel combustion technique in presence of air using boron as flux and urea as a fuel. A comparative study of the prepared materials was carried out with and without the addition of boric acid. The boric acid was playing the important role of flux and reducer simultaneously. The peaks available in the XPS spectra of BaAl2O4:Eu2+ at 1126.5 and 1154.8 eV was ascribed to Eu2+(3d5/2) and Eu2+(3d3/2) respectively which confirmed the presence of Eu2+ ion in the prepared lattice. Morphology of phosphors was characterized by tunneling electron microscopy. XRD patterns revealed a dominant phase characteristics of hexagonal BaAl2O4 compound and the presence of dopants having unrecognizable effects on basic crystal structure of BaAl2O4. The addition of boric acid showed a remarkable change in luminescence properties and crystal size of nanophosphors. The emission spectra of phosphors had a broad band with maximum at 490–495 nm due to electron transition from 4f65d1 → 4f7 of Eu2+ ion. The codoping of the rare earth (RE3+=Y, Pr) ions help in the enhancement of their luminescent properties. The prepared phosphors had brilliant optoelectronic properties that can be properly used for solid state display device applications.The authors gratefully recognize the financial support from the University Grant Commission (UGC), New Delhi [MRP-40-73/2011(SR)] and the European Commission through Nano CIS project (FP7-PEOPLE-2010-IRSES ref. 269279).Singh, D.; Tanwar, V.; Simantilke, AP.; Marí, B.; Kadyan, PS.; Singh, I. (2016). Rapid synthesis and enhancement in down conversion emission properties of BaAl2O4:Eu2+,RE3+ (RE3+=Y, Pr) nanophosphors. Journal of Materials Science: Materials in Electronics. 27(3):2260-2266. https://doi.org/10.1007/s10854-015-4020-1S22602266273J.S. Kim, P.E. Jeon, J.C. Choi, H.L. Park, S.I. Mho, G.C. Kim, Appl Phys Lett 84, 2931 (2004)D. Jia, D.N. Hunter, J Appl Phys 100, 1131251 (2006)H. Aizawa, T. Katsumata, J. Takahashi, K. Matsunaga, S. Komuro, T. Morikawa, E. Toba, Rev Sci Instrum 74, 1344 (2003)C.N. Xu, X.G. Zheng, M. Akiyama, K. Nonaka, T. Watanabe, Appl Phys Lett 76, 179 (2000)C. Feldmann, T. Justel, C.R. Ronda, P.J. Schmidt, Adv Funct Mater 13, 511 (2004)P.J. Saines, M.M. Elcombe, B.J. Kennedy, J Solid State Chem 179, 613 (2006)R. Sakai, T. Katsumata, S. Komuro, T. Morikawa, J Lumin 85, 149 (1999)T. Aitasalo, P. Deren, J Solid State Chem 171, 114 (2003)S. Nakamura, T. Mukai, M. Senoh, J Appl Phys 76, 8189 (1994)S.H.M. Poort, G. Blasse, J Lumin 72, 247 (1997)P. Mingying, H. Guangyan, J Lumin 127, 735 (2007)X. Linjiu, H. Mingrui, T. Yanwen, C. Yongjie, K. Tomoaki, Z. Liqing, W. Ning, Jap J Applied Physics 46, 5871 (2007)T. Aitasalo, J. Hölsä, H. Jungner, M. Lastusaari, J. Niittykoski, J Phys Chem B 110, 4589 (2006)R. Stefani, L.C.V. Rodrigues, C.A.A. Carvalho, M.C.F.C. Felinto, H.F. Brito, M. Lastusaari, J. Hölsä, Opt Mater 31, 1815 (2009)M. Peng, G. Hong, J Lumin 127, 735 (2007)V. Singh, V. Natarajan, J.J. Zhu, Opt Mater 29, 1447 (2007)X.Y. Chen, C. Ma, X.X. Li, C.W. Shi, X.L. Li, D.R. Lu, J Phys Chem C 113, 2685 (2009)A.J. Zarur, J.Y. Ying, Nature 403, 65 (2000)J. Chen, F. Gu, C. Li, Cry Growth Des 8, 3175 (2008)J. Zhang, M. Yang, H. Jin, X. Wang, X. Zhao, X. Liu, L. Peng, Mater Res Bull 47, 247 (2012)P. Maślankiewicz, J. Szade, A. Winiarski, Ph Daniel, Cryst Res Technol 40, 410 (2005)Y.J. Chen, G.M. Qiu, Y.B. Sun et al., J Rare Earths 20, 50 (2002)F.C. Palilla, A.K. Levine, M.R. Tomkus, J Electrochem Soc 115, 642 (1968)J. Niittykoski, T. Aitasalo, J. Holsa, H. Jungner, M. Lastusaari, M. Parkkinen, M. Tukia, J Alloys Compd 374, 108 (2004)A. Nag, T.R.N. Kutty, J Alloys Compd 354, 221 (2003)D. Haranath, P. Sharma, H. Chander, J Phys D Appl Phys 38, 371 (2005

Novel composite implant in craniofacial bone reconstruction

Bioactive glass (BAG) and polymethyl methacrylate (PMMA) have been used in clinical applications. Antimicrobial BAG has the ability to attach chemically to surrounding bone, but it is not possible to bend, drill or shape BAG during the operation. PMMA has advantages in terms of shaping during the operation, but it does not attach chemically to the bone and is an exothermic material. To increase the usefulness of BAG and PMMA in skull bone defect reconstructions, a new composite implant containing BAG and PMMA in craniofacial reconstructions is presented. Three patients had pre-existing large defects in the calvarial and one in the midface area. An additive manufacturing (AM) model was used preoperatively for treatment planning and custom-made implant production. The trunk of the PMMA implant was coated with BAG granules. Clinical and radiological follow-up was performed postoperatively at 1 week, and 3, 6 and 12 months, and thereafter annually up to 5 years. Computer tomography (CT) and positron emission tomography (PET-CT) were performed at 12 and 24 months postoperatively. Uneventful clinical recovery with good esthetic and functional outcome was seen. CT and PET-CT findings supported good clinical outcome. The BAG–PMMA implant seems to be a promising craniofacial reconstruction alternative. However, more clinical experience is needed

Thermoluminescence Study of Persistent Luminescence Materials Eu2+Eu^ {2+} and R3+R^ {3+}Doped Calcium Aluminates, CaAl2O4CaAl_{2}O_{4} Eu2+Eu^ {2+}, R3+R^ {3+}

Thermoluminescence properties of the Eu2+-, R3+-doped calcium aluminate materials, CaAl2O4:Eu2+,R3+, were studied above room temperature. The trap depths were estimated with the aid of the preheating and initial rise methods. The seemingly simple glow curve of CaAl2O4:Eu2+ peaking at ca. 80 degrees C was found to correspond to several traps. The Nd3+ and Tm3+ ions, which enhance most the intensity of the high-temperature TL peaks, form the most suitable traps for intense and long-lasting persistent luminescence, too. The location of the 4f and 5d ground levels of the R3+ and R2+ ions were deduced in relation to the band structure of CaAl2O4. No clear correlation was found between the trap depths and the R3+ or R2+ level locations. The traps may thus involve more complex mechanisms than the simple charge transfer to (or from) the R3+ ions. A new persistent luminescence mechanism presented is based on the photoionization of the electrons from Eu2+ to the conduction band followed by the electron trapping to an oxygen vacancy, which is aggregated with a calcium vacancy and a R3+ ion. The migration of the electron from one trap to another and also to the aggregated R3+ ion forming R2+ (or R3+-e-) is then occurring. The reverse process of a release of the electron from traps to Eu2+ will produce the persistent luminescence. The ability of the R3+ ions to trap electrons is probably based on the different reduction potentials and size of the R3+ ions. Hole trapping to a calcium vacancy and/or the R3+ ion may also occur. The mechanism presented can also explain why Na+, Sm3+, and Yb3+ suppress the persistent luminescence

Effect of temperature on the luminescence processes of SrAl2O4:Eu2+

RadiochThe UV excited and persistent luminescence properties as well as thermoluminescence (TL) of Eu2+ doped strontium aluminates, SrAl2O4:Eu2+ were studied at different temperatures. Two luminescence bands peaking at 445 and 520 nm were observed at 20 K but only the latter at 295 K. Both Sr-sites in the lattice are thus occupied by Eu2+ but at room temperature efficient energy transfer occurs between the two sites. The UV excited and persistent luminescence spectra were similar at 295 K but the excitation spectra were different. Thus the luminescent centre is the same in both phenomena but excitation processes are different. Two TL peaks were observed between 50 and 250 °C in the glow curve. Multiple traps were, however, observed by preheating and initial rise methods. With longer delay times only the high temperature TL peak was observed. The persistent luminescence is mainly due to slow fading of the low temperature TL peak but the step-wise feeding process from high temperature traps is also probable