Search

The synchrotron radiation luminescence and excitation spectra of the Eu2+ doped M2MgSi2O7 (M = Ca, Sr, Ba) materials were investigated at the SUPERLUMI station of HASYLAB at DESY, Germany. The measurement of the band gap (Eg) energy of all three host lattices using the excitation spectra of Eu2+ gave values around 7 eV. The measured band gap energies were very similar but slightly higher than those calculated with the DFT-methods. The effect of R3+ co-doping was studied at different temperatures between 10 K and room temperature. A significant increase in the band gap energy was observed with decreasing temperature. In contrast, no noteworthy change in this value was observed as a function of the R3+ co-doping ion.

High-resolution (< 1 Aa) VUV emission and excitation spectra as well as luminescence decay kinetics have been studied for several fluoride crystals containing Gd3+ and Lu3+ ions under excitation by synchrotron radiation. The obtained results evidently show that VUV luminescence (~ 10 eV) observed from these crystals originates from 5d-4f transitions in the Gd3+ and Lu3+ ions. Only fast spin-allowed 5d-4f luminescence is observed from Gd compounds, whereas both spin-forbidden and spin-allowed 5d-4f luminescence has been detected from Lu compounds, the latter being observed only at high enough (T > 100 K) temperatures.

The crystal structure, electronic states and VUV spectroscopic behaviour of Cs2KYF6doped with Pr3+ions have been investigated both by experimental and theoretical methods. Cs2KYF6(${\rm F}m{\bar 3}m$, Z = 4, a = 945.5(3) pm, R1all= 0.0297) crystallizes with the cubic elpasolite type of structure. The local relaxation of the activator ions in the host lattices has been calculated by the projector augmented wave method (computer code VASP). The electronic states have been calculated using a spin density functional procedure based on the atomic sphere approximation (computer code ASW). VUV spectroscopic measurements show fast 4f15d1→ 4f2emission of nanosecond duration as well as slow 4f2→ 4f2emission depending on the excitation energy which indicates the occupation of different sites in the host lattice. This assumption was verified by a recently developed quantum mechanical method. The combination of the experimental and the theoretical results show that the Pr3+ions are occupying three different sites, namely the Y3+and the Cs+site as well as the K+site.

Processes of efficient creation of groups of electronic excitations (EEs) or defects have been considered for radiation-sensitive (alkali halides) and radiation-resistant (metal oxides) single crystals. In MgO, pure or doped with Be2+, Ca2+ and Al3+ ions, the 7.63 eV edge emission of anion excitons is efficiently excited at 10 K in a wide region of 30–90 eV. Multiplication process with the creation of secondary electron–hole pairs and the decay process of cation excitations are compared in crystals of two types: (i) KCl, KBr and LiF, where anion excitons and valence holes undergo self-trapping and (ii) a MgO crystal, where no self-trapping of excitations occurs. In alkali halides, a group of spatially correlated EEs, formed at photon absorption, is transformed into an F–I–VK triplet of defects at 5 K or into a temperature-stable F centre and a trihalide molecule (e.g., Br3–) at 295 K. In BaMgAl10O17:Eu at 295 K, the 2.72 eV emission of Eu2+ centres with quantum yield of 1.1–3.5 at the excitation by photons of 13–30 eV has been obtained. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The International Conference Functional Materials and Nanotechnologies (FM&NT - 2013) was held in Tartu, 21-24 April 2013 at the Dorpat Conference Centre. The conference was organised by Institute of Physics, University of Tartu. The FM&NT conference series was started in 2006 by scientists from the Institute of Solid State Physics, University of Latvia. It is an annual conference bringing together researchers from the whole world. The warm and open atmosphere of this scientific conference has turned it into event where people from different fields meet under the common name of functional materials and nanotechnology. It is particularly important for early stage scientists who are looking for new knowledge and contact with people from various fields. Our Latvian colleagues with their success in internationalization made us neighbouring Estonians so envious that we could not withstand proposing that we host the conference in every second year in Estonia. Actually this is in a way the continuation of the idea of the famous Baltic seminars which took place over several decades during the last century. Due to political constraints these seminars were only opened to scientist of the former Eastern European countries, but which were extremely popular and attracted attendees from over the whole Soviet Union. Much fruitful cooperation started from the initial personal contacts of scientists at these seminars held twice per year, once in Latvia and the second time in Estonia. At the last FM&NT 2012 conference, the decision was made that Institute of Physics, University of Tartu would organise the event in Tartu in 2013. Along with traditional topics such as multifunctional materials, nanomaterials, materials for sustainable energy applications and theory, this conference focused on studies using synchrotron radiation and other novel light sources. The number of registered participants from 21 countries was nearly 300. During the three days of the conference 14 invited, 45 oral, and 5 commercial talks were delivered and more than 200 posters were presented. In the framework of conference more than 20 papers were submitted to a topical issue of Physica Scripta. Based on the work presented at the conference, 62 articles are included in this volume of IOP Conference Series: Materials Science and Engineering. Additional information about FM&NT-2013 is available at its homepage http://fmnt.ut.ee/. The Organizing Committee would like to thank all the speakers, contributors, session chairs, referees and other involved staff for their efforts in making FM&NT-2013 successful. Special thanks for their hard work dealing with the conference papers goes to the Guest Editors: Professor Mikhail Brik, Dr Svetlana Zazubovits, Dr Arvo Kikas, Dr Rainer Parna. The Organizing Committee hopes that Conference gave participants good insight into recent developments in nanotechnology, sustainable energetics, processing and modelling of multifunctional materials and research done using synchrotron radiation or other novel light sources. We sincerely hope that conference has provided support for the sharing of information and has brought together many young and experienced scientists from different fields, leading to fruitful discussions. We hope that all participants had good and memorable time in Tartu. On the behalf of organising committee Professor Ergo Nommiste Dr Marco Kirm Dr Toomas Plank The PDF also contains lists of the committees, the conference photograph and the sponsor's logos.

Pure and Ce doped nanoporous 12CaO•7Al2O3 (C12A7) oxides were synthesized using self-propagating combustion method and solid state reaction. Time-resolved photoluminescence method at low temperatures was applied in studies of powder samples and ceramics, which were obtained in a melt-solidification process partly replacing encaged oxygen ions with electrons. In pure C12A7 with the encaged electrons broad luminescence bands peaked at 3.3 and 5.0 eV were revealed. The first one corresponds to the luminescence due to the encaged oxygen ions and latter one is assigned to the recombination of electrons and holes localized on the framework oxygen ions. Ce doping introduces emission band at 3.0 eV due to 5d-4f transitions with several decay components in nanosecond range. The Ce 5d-4f luminescence is efficiently excited through Ce intra-center absorption as well as through energy transfer processes in the intrinsic absorption region of C12A7 above energy gap at 7.0 eV.

The synchrotron radiation luminescence and excitation spectra of the Eu2+ doped M2MgSi2O7 (M = Ca, Sr, Ba) materials were investigated at the SUPERLUMI station of HASYLAB at DESY, Germany. The measurement of the band gap (Eg) energy of all three host lattices using the excitation spectra of Eu2+ gave values around 7 eV. The measured band gap energies were very similar but slightly higher than those calculated with the DFT-methods. The effect of R3+ co-doping was studied at different temperatures between 10 K and room temperature. A significant increase in the band gap energy was observed with decreasing temperature. In contrast, no noteworthy change in this value was observed as a function of the R3+ co-doping ion.

High-resolution (< 1 Aå) VUV emission and excitation spectra as well as luminescence decay kinetics have been studied for several fluoride crystals containing Gd3+ and Lu3+ ions under excitation by synchrotron radiation. The obtained results evidently show that VUV luminescence (~ 10 eV) observed from these crystals originates from 5d-4f transitions in the Gd3+ and Lu3+ ions. Only fast spin-allowed 5d-4f luminescence is observed from Gd compounds, whereas both spin-forbidden and spin-allowed 5d-4f luminescence has been detected from Lu compounds, the latter being observed only at high enough (T > 100 K) temperatures.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF.