bluuebunny/crossref_metadata_2025_split huggingface dataset:
Luminescence of ZrO2 and HfO2 thin films implanted with Eu and Er ions
Authors: Lange S. , Kiisk V. , Aarik J. , Kirm M. , Sildos I. 
Published: March 2007

AbstractA spectroscopic study of Eu‐ and Er‐implanted ZrO2 and HfO2 thin films was performed. Photoluminescence (PL) of trivalent ions under band‐to band excitation of the host was observed. Annealing up to 1100 °C was required to maximize the PL signal intensity. The Eu3+ ion was used as a probe of local structure. The PL excitation spectra were recorded both for intrinsic and impurity‐related emission. Different channels of indirect excitation of the RE ions were revealed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dielectric properties of Li doped Li‐Nb‐O thin films
Authors: Perentzis G. , Horopanitis E. E. , Papadimitriou L. , Ďurman V. , Šály V. , Packa J. 
Published: March 2007

AbstractLithium niobate LiNbO3 was prepared as a thin film layered structure deposited on stainless steel substrate using e‐gun evaporation. The Li doping was provided for by the formation of Li‐Nb‐O/Li/LiNb‐O sandwich structure and annealing at about 250 °C. AC impedance spectroscopy measurements were performed on the samples at temperatures from the interval between 28 and 165 °C and in a frequency range of 10–3 to 106 Hz. Using the values Z ′ and Z ″ at different frequencies, the dielectric parameters – parts of the complex permittivity ϵ′ and ϵ″ and loss tangent tan δ were calculated. The results prove validity of the proposed equivalent circuit containing parallel RC elements connected in series where the first RC element represents the bulk of material and the second RC element belongs to the double layer at the metal interface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurements of the low frequency dispersion in electrical grade ceramics
Authors: Ďurman V. , Packa J. , Lelák J. , Šály V. 
Published: March 2007

AbstractThe paper reports on the advanced technique of the dielectric response and conductivity calculation based on the recovery voltage measurements. The new calculation method has been developed and applied to assessment of an electrical grade ceramics made from quartz and alumina porcelain. The measured data were converted into the form of complex permittivity. Experimental results show the existence of the polarization process with relaxation frequency of about 0.001 Hz. The relaxation frequency and the conductivity appear to be very sensitive to the temperature variation. They could be prospective indicators of the changes generated by temperature and ageing of material. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
EPR hyperfine structure of F‐type centres in pure LiBaF3 crystal
Authors: Fedotovs A. , Elsts E. , Rogulis U. , Gulans A. , Tale I. , Nikl M. , Ichinose N. , Shimamura K. 
Published: March 2007

AbstractWe studied EPR spectra of pure LiBaF3 sample of high quality. For EPR measurements LiBaF3 sample was X‐irradiated at room temperature, however spectra could be observed at low temperatures ‐ at 77 K. All hyperfine structure lines of F‐type centre could be well resolved contrary to our earlier studies of Fe doped LiBaF3 crystal. Qualitative analysis with g‐tensor parameters derived from magneto‐optical measurements showed that the F‐type centre observed earlier by MCD‐EPR techniques is the same F‐type centre we observe with the EPR. We analyse origin of the hyperfine structure of the EPR spectra and their angular dependencies and discuss the structure of F‐type centres in the LiBaF3 crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling irradiation induced metastability in ceramic thin films
Authors: Ossi Paolo M. 
Published: March 2007

AbstractAmorphous, or crystalline phase nucleation in ion bombarded ceramic films is analysed by the Interface Migration‐Charge Transfer (IMCT) atomistic model. The development of a dense collision cascade leads to enrichment of one of film constituents at the cascade‐crystal interface, where non‐equilibrium profiles both of composition and of electronic density result. Local charge transfer reactions (CTR) simulate system relaxation via formation of dimers of an effective compound. We calculate the energy cost and the enthalpy change to produce one such dimer for a representative set of binary and ternary irradiated compounds. Threshold values of both quantities separate amorphised from crystalline compounds under ion bombardment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical defects in LiNbO3 crystals induced by femtosecond laser irradiation
Authors: Galinetto P. , Grando D. , Mozzati M. C. , Ballarini D. , Giulotto E. 
Published: March 2007

AbstractMicrostructural modifications, induced by femtosecond laser irradiation on Lithium Niobate (LN) crystals were investigated by means of optical microscopy and micro‐Raman spectroscopy. Commercial z‐cut congruent LN substrates were irradiated with focused ultra‐short laser pulses at 810 nm. At the focus region either structural changes or material removal were observed by varying the irradiation conditions. The mapping of Raman spectrum revealed the insurgence of Raman modes, which are forbidden in the used scattering geometry. This phenomenon increases gradually by approaching the ablation region. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence of Ce‐doped borate‐oxyfluoride glass ceramics
Authors: Dimitrocenko L. , Rogulis U. , Veispals A. , Springis M. , Kulis P. , Fedotovs A. , Mishnev A. 
Published: March 2007

AbstractIn the present work we studied the possibility to obtain oxyfluoride glass ceramics based on a lithium and potassium borate glasses with addition of fluorides. Lithium‐borate glasses without lanthanum fluoride are transparent up to 275 nm. In samples with LaF3 doped with Ce‐activator, an additional absorption at about 300 nm and intense photoluminescence could be observed. Ce‐doped potassium‐borate glass with addition of fluorides LaF3, LiF and GdF3 was milky and not transparent, an intense photoluminescence has been observed, X‐ray diffraction measurements showed a presence of well‐pronounced crystalline phases of LiF as well as of GdBO3. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The dose dependence and the firing effects on the thermoluminescence of quartz
Authors: Halperin Abraham 
Published: March 2007

AbstractPapers on the dose dependence of thermoluminescence of quartz have been published in recent years by research groups from various countries. These papers show that untreated quartz gives very strong superlinearity (up to slopes of 3 in a log‐log scale). Almost all the investigators who describe the above effects refer to a theoretical paper by Kristianpoller et al. (J. Phys. D: Appl. Phys. 7, 1063 (1974) [6]) which shows that adding a competing trap to the energy system of quartz, gives a set of equations which can be solved numerically for various sets of given parameters, when results explain all the above effects. Unlike other investigators who used quartz powders, we preferred to use single crystals of quartz. For better resolution of two or more neighboring thermoluminescence peaks, we reduced the rate of heating in the thermoluminescence measurements to 10 degrees per minute. We found that limiting the temperature in the TL heatings during the set of doses to 400‐450 K, gave extremely high superlinearity (slopes close to 7). A set of decreasing doses was found to reduce the high superlinearity and to increase the 430 K peak by more than 3 orders of magnitude without any firing. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Intrinsic defect processes in bixbyite sesquioxides
Authors: Chroneos A. , Levy M. R. , Stanek C. R. , McClellan K. , Grimes R. W. 
Published: March 2007

AbstractAtomic scale simulation techniques have been employed to study the intrinsic defect processes of a range of bixbyite sesquioxides using a transferable set of interatomic potentials. The efficacy of the approach is demonstrated through comparison of the predictions to previous experimental and theoretical (density functional theory) results. The aim here is to provide data that can be used as a basis for further structural optimizations targeting the use of mixed bixbyite sesquioxides as buffer layers for the fabrication of epitaxically coated, high‐temperature superconductors on different substrates. The internal energies for the three possible intrinsic defect reactions (Schottky, cation Frenkel and oxygen Frenkel) have been calculated with regard to the application of these oxides for scintillator radiation detectors. The lowest energy intrinsic process is the oxygen Frenkel for all the bixbyite sesquioxides considered. Surprisingly, the oxygen Frenkel energy does not depend greatly on the host cation radius. The implication of this result is that the lowest energy intrinsic defect occurs on the oxygen sublattice and therefore will be most likely to serve as electron and hole traps. These traps are important for the scintillation properties of bixbyite sesquioxides as they act as non‐radiative centers reducing the efficiency of scintillator materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural study of NaNO2 embedded into porous glass
Authors: Rysiakiewicz‐Pasek E. , Maczka M. , Urbanowicz A. 
Published: March 2007

AbstractTemperature‐dependent Raman study of NaNO2 confined within porous glass with a pore size of 46 nm has been performed. It is demonstrated that the bandwidths and frequencies of the Raman bands as a function of temperature show similar behaviour, but not identical, as those observed for bulk NaNO2. This result indicates that the first‐order phase transition mechanism is only slightly modified by embedding NaNO2 into the porous glass. It seems that formation of “premelted state” is not significant in the studied material, at least up to 40‐50 K above Tc. At higher temperatures, however, a significant increase of bandwidth of the 1326 cm–1 band is observed, which could indicate appearance of “premelted” state. The dielectric measurements are consistent with this view since they show large increase of dielectric permittivity above 480 K, well below the NaNO2 melting temperature (554 K). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Native and radiation‐induced two‐fold coordinated sites in nanostructured SnO2:SiO2
Authors: Brovelli S. , Chiodini N. , Lauria A. , Meinardi F. , Paleari A. 
Published: March 2007

AbstractRadiation‐induced spectral modifications of the 5 eV excited photoluminescence (PL) of oxygen vacancies have been found in a nanostructured silica‐based material. This system, made up of SnO2 nanocrystals embedded in amorphous SiO2, is generated by nano‐clustering in oversaturated Sn‐doped silica produced by sol‐gel method. Treatment in oxygen‐poor atmosphere introduces oxygen deficiency in the glassy host and a photo‐reactive SnO‐like interphase at the SnO2 nanocrystal surface. PL measurements initially show native PL activity at 2.7 eV excited at 5 eV, ascribable to oxygen vacancies in intrinsic two‐fold coordinated Si sites. Prolonged UV irradiation at 4.7 eV (fourth harmonic of Nd‐YAG pulsed laser) gives rise to extrinsic PL activity at 3.1 eV, ascribable to Sn‐variant of oxygen vacancy. The results suggest that the UV irradiation causes a progressive release of Sn from the nanophase surface to the glassy network in oxygen vacancy sites. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Damage creation in LiF and NaCl crystals irradiated with swift heavy ions at 8 and 300 K
Authors: Schwartz K. , Lang M. , Neumann R. , Sorokin M. V. , Trautmann C. , Volkov A. E. , Voss K.‐O. 
Published: March 2007

AbstractSingle crystals of LiF and NaCl were irradiated at 8 and 300 K with different ions (12C to 238U) of MeV‐GeV energy in the electronic stopping regime. The ion‐induced damage was studied by optical absorption, thermo‐stimulated luminescence, and scanning force microscopy. The concentration of the color centers depends on the energy loss of the ions. In both crystals, the irradiation with heavy ions (Au, Pb, U) results in a higher F center concentration at 8 K than at 300 K; for light ions (C, Ti, Ni) the opposite effect takes place. The observed results can be explained by ion induced local heating. Contrary to color‐center creation, the formation of nano‐sized surface hillocks does not depend on the irradiation temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies of the location of precious metals in nanocrystalline titanium dioxide using XRD and XANES
Authors: Rammutla K. E. , Savin S. L. P. , Matshaba M. G. , Chadwick A. V. , Ngoepe P. E. 
Published: March 2007

AbstractAu, Ag, Pt and Pd doped TiO2 nanocrystals were prepared using sol‐gel routes. X‐ray Near Edge Structure (XANES) was used to study the location of these precious metal dopants in nanocrystalline TiO2. The effects of these dopants on the phase transformation and grain growth were investigated using X‐ray diffraction (XRD). Two dopant concentrations i.e. 1 and 5% were studied and similar results were found. Silver and Palladium initially form oxides but annealing at high temperatures converts them to metals. Gold and and silver do not affect the anatase ‐ rutile transformation temperature whereas palladium and platinum do. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The peculiarities of hydroxyl impurity behaviour in crystalline LiF and MgO matrices under the action of radiation
Authors: Akhvlediani Z. , Kvatchadze V. 
Published: March 2007

AbstractThe comparative analysis of the results obtained in the investigation of infrared absorption spectra of irradiated lithium fluoride and magnesium oxide samples has been made. For irradiation of the samples X‐ray generator, Co60 source and different reactors were used. The universal linear dependence of bands caused by centers containing OH– ions was observed for the first time in the irradiated MgO samples. The thermal treatment of irradiated LiF crystals have clearly showed the interconnection of hydroxyl ions and hydrogen products of their dissociation.The significant difference in the behaviour of impurity hydroxyl ions in matrices of the mentioned ionic compounds was observed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of TiO2–SiO2glass over a wide spectral range
Authors: Smith D. Y. , Black C. E. , Homes C. C. , Shiles E. 
Published: March 2007

AbstractOptical properties of vitreous SiO2with 7.4 wt.% TiO2are found by dispersion analysis of reflectivity measured in the infrared, visible, and ultraviolet augmented with literature values of vacuum‐ultraviolet reflectivity and absorption. The principal infrared absorption associated with the titanium dopant occurs at 950 cm−1in a deep minimum of the host silica absorption. We attribute this to a perturbation of the silica's absorption at 1076 cm−1involving oxygen atoms bridging SiO4and TiO4tetrahedra. Strong ultraviolet absorptions of Ti4+occur just below the silica exciton peak between 5.5 and 7.8 eV. We attribute these to charge‐transfer transitions at TiO4tetrahedra; i.e., bound excitons consisting of a Ti3+ion and a hole shared by four oxygen neighbours. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence of oxygen related defects in zirconia nanocrystals
Authors: Smits K. , Grigorjeva L. , Łojkowski W. , Fidelus J. D. 
Published: March 2007

AbstractThe luminescence of undoped tetragonal structure ZrO2 nanocrystals was studied. The luminescence intensity depends on oxygen content in gases mixture in which the nanocrystals were annealed. The distorted Zr‐O bond is suggested to be the recombination center for band carriers. The oxygen deficient defect is proposed to be responsible for photoluminescence. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Li‐ion conducting organic‐inorganic hybrid electrolytes derived from TEOS and methacrylates
Authors: Zelazowska E. , Borczuch‐Laczka M. , Rysiakiewicz‐Pasek E. 
Published: March 2007

AbstractLi‐ion conductive organic‐inorganic hybrid electrolytes with the ionic conductivities of 10–3 ‐ 10–2 Scm–1 have been prepared by sol‐gel route from tetraethyl orthosilicate TEOS, poly(ethylene oxide), ethyl methacrylate, ethylene glycol dimethacrylate, butyl methacrylate, organic solvents and lithium perchlorate (0.01 wt%). The results of morphology and structure investigation by scanning electron microscopy equipped with energy dispersive X‐ray spectroscopy (SEM/EDX), Fourier Transform Infrared Spectroscopy and 29Si MAS Nuclear Magnetic Resonance have revealed strong influence of organic modifications, resulted in direct chemical bonds between organic and inorganic components and poly‐condensation process overlapped with crosslinking polymerization in hybrids prepared with ethyl methacrylate. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoluminescent characteristics of Actinolite‐Teflon composites for gamma high‐doses
Authors: Melo Adeilson P. , Valerio Mário E. G. , Caldas Linda V. E. 
Published: March 2007

AbstractIn this work a preliminary study of the thermoluminescent (TL) dosimetric properties of the Brazilian actinolite:Ca2(Mg,Fe)5(Si8O22)(OH)2 (silicate of the Jade family) was undertaken for gamma high‐doses. Actinolite occurs in several regions in the world. In this work actinolite in the form of rude mineral from Governador Valadares, Minas Gerais, Brazil, was studied. The natural actinolite samples were powdered, and the selected grains were mixed with Teflon in the proportion 2(Teflon):1(Actinolite). The mixture was pressed and sintered for production of pellets of composites Actinolite ‐ Teflon. The glow curves present two peaks at 125 °C and 210 °C. The TL response reproducibility presents a maximum variation coefficient of 4.8%. The calibration curve is linear between 0.5 Gy and 1 kGy for pellets irradiated with gamma radiation (60Co) and between 0.5 Gy and 10 Gy for pellets irradiated with X‐rays (33 keV). The TL response presents an energy dependence of 26% for X‐rays between 27 and 41 keV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Irradiation effects in BaF2:CuCl2 and BaF2:Mn,Ce crystals
Authors: Kristianpoller N. , Chen W. , Weiss D. , Kuzmin D. , Chen R. 
Published: March 2007

AbstractEffects of X, β and VUV radiation were studied in BaF2:CuCl2 and BaF2:Mn,Ce crystals. Methods of optical absorption and of luminescence were applied; X‐luminescence (XL), photoluminescence (PL), thermoluminescence (TL), photo‐transferred TL (PTTL) and optically stimulated luminescence (OSL) as well as emission and excitation spectra were measured. Optical stimulation for PTTL and OSL investigations was carried out at liquid nitrogen temperature (LNT) in samples that had previously been X or β irradiated at room temperature (RT) and the results were compared to those obtained in nominally pure BaF2 crystals. The TL excitation spectra showed maxima at the long‐wavelength side of the first exciton band. In the VUV induced TL, some of the peaks appeared at the same temperature as in the X‐induced TL, indicating that the same radiation‐induced traps were created by the different types of radiation. The TL efficiency of some of the crystals was found to be of the same order of magnitude as that of the known TL dosimetric material LiF:Mg,Ti (TLD 100). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence characteristics of the LPE‐grown undoped and In‐doped ZnO thin films and bulk single crystals
Authors: Pejchal J. , Kagamitani Y. , Ehrentraut D. , Sato H. , Odaka H. , Hatanaka H. , Nikl M. , Yoshikawa A. , Fukumura H. , Fukuda T. 
Published: March 2007

AbstractThe time‐resolved emission spectroscopy using the fs‐laser pulse and ps X‐ray excitations was employed to compare the luminescence characteristics of the liquid phase epitaxy grown ZnO films and the hydrothermally grown single crystals. Reabsorption of the excitonic emission is demonstrated in the bulk ZnO. In the In‐doped films the donor‐acceptor pair recombination luminescence was evidenced above 400 nm and its decay was found to obey the t–1 law. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time development of scintillating response in Ce‐ or Pr‐doped crystals
Authors: Mares J. A. , Beitlerova A. , Nikl M. , Vedda A. , D'Ambrosio C. , Blazek K. , Nejezchleb K. 
Published: March 2007

AbstractTime development of a Nphels/MeV photoelectron yield of various Ce and Pr‐doped inorganic crystals (mainly garnets, perovskites and silicates) was studied in detail. Slow scintillation decay components influence time dependence, especially at those scintillators containing Lu as lattice ions where an increase of Nphels per 1 MeV in the time span 0.25–5 µs is more than 50%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High resolution spectroscopic properties and emission decay of rare‐earth doped transparent laser ceramics
Authors: Lupei V. , Lupei A. , Ikesue A. 
Published: March 2007

AbstractThe paper discusses the use of high‐resolution spectroscopy and emission decay for investigation of the variety, nature, structure and distribution of the centers formed by the rare earth ions in transparent polycrystalline ceramics of cubic oxide laser materials (garnets and sesquioxides). It is shown that for ceramics with grains of the order of tens of microns the spectroscopic and population dynamics properties of the doping ions can be described consistently based on the crystal structure of the host material and assuming random distribution even at concentrations much larger than that available for the single crystals. It is inferred that from spectroscopic point of view these ceramics can substitute the crystals as laser materials and their enhanced compositional versatility enables tailoring of new laser materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermally stimulated polarisation and depolarisation currents in SLS glass exchanged with copper
Authors: Suszynska M. , Macalik B. , Krajczyk L. , Capelletti R. , Mora C. 
Published: March 2007

AbstractSoda‐lime silicate glasses, with compositions corresponding to the immiscibility range, were studied to characterise their electrical properties and to determine the dependence of these characteristics on the glass microstructure. Dielectric measurements, analysed in terms of Maxwell/Wagner/Sillars theories of inhomogeneous dielectrics, have been used to investigate the phase separation characteristics of soda‐lime silicate glasses exchanged by copper. Such measurements are shown to provide evidences of the continuous or discontinuous nature of separated phases, the presence of which has been confirmed by the transmission electron microscopy observations. The results indicated that dielectric measurements are particularly useful in following phase‐separation‐processes in the oxide glasses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge‐ordering in La0.333Ca0.667MnO3
Authors: Nikiforov A. E. , Gontchar L. E. , Popov S. E. , Kotomanov S. V. , Larin A. V. 
Published: March 2007

AbstractWithin the framework of strong electron‐lattice interaction of Mn3+ ions and orbital dependent exchange interaction model, the crystal and magnetic structures of charge ordered phase La1/3Ca2/3MnO3 are studied. The calculation results are in agreement with the “Wigner crystal” model. The estimated superexchange parameters confirm the qualitative conclusions of experimental works about frustrated magnetic structure with magnetic supercell (3a × b × 2c). The values of hyperfine magnetic fields on 55Mn nuclei in different charge states in charge ordering phase are calculated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)