共查询到20条相似文献,搜索用时 31 毫秒
1.
Bastian Henke Stefan Schweizer Jacqueline A. Johnson Denis T. Keane 《Journal of synchrotron radiation》2007,14(3):252-256
The energy‐dependent scintillation intensity of Eu‐doped fluorozirconate glass‐ceramic X‐ray detectors has been investigated in the energy range from 10 to 40 keV. The experiments were performed at the Advanced Photon Source, Argonne National Laboratory, USA. The glass ceramics are based on Eu‐doped fluorozirconate glasses, which were additionally doped with chlorine to initiate the nucleation of BaCl2 nanocrystals therein. The X‐ray excited scintillation is mainly due to the 5d–4f transition of Eu2+ embedded in the BaCl2 nanocrystals; Eu2+ in the glass does not luminesce. Upon appropriate annealing the nanocrystals grow and undergo a phase transition from a hexagonal to an orthorhombic phase of BaCl2. The scintillation intensity is investigated as a function of the X‐ray energy, particle size and structure of the embedded nanocrystals. The scintillation intensity versus X‐ray energy dependence shows that the intensity is inversely proportional to the photoelectric absorption of the material, i.e. the more photoelectric absorption the less scintillation. At 18 and 37.4 keV a significant decrease in the scintillation intensity can be observed; this energy corresponds to the K‐edge of Zr and Ba, respectively. The glass matrix as well as the structure and size of the embedded nanocrystals have an influence on the scintillation properties of the glass ceramics. 相似文献
2.
Soda-lime-silicate glasses doped with different rare-earth oxides (La2O3, CeO2, Nd2O3, Gd2O3 and Y2O3) of 1 mol% content were prepared with the traditional melting-quenching methods. In order to reveal the effects of rare-earth elements on the behavior of soda-lime-silicate glass, the structure of soda-lime-silicate glasses doped with different rare-earth oxides were determined with Fourier transform infrared spectrometer using the KBr method, and viscosity of glass melts were measured by the rotating crucible viscometer, the melting temperature of the studied glasses were derived on the basis of Arrhenius Equation, moreover the density, bending strength and molar volume were measured and calculated. The effect of rare-earth dopants on the structure of soda-lime-silicate was analyzed by a shift of peak position and variation in the full-width at half-maximum. The effect of doping rare-earth oxides into glass on the viscosity, density and bending strength was interpreted by changing in structure of soda-lime-silicate glasses doped with rare-earth oxides. 相似文献
3.
4.
Glasses in the PbF2-PbO-SiO2 system doped with 1 mol % of rare-earth elements (Nd3+, Er3+, or Yb3+) are synthesized and studied. The glasses were heat-treated in order to obtain glass ceramics with a fluoride crystalline phase. The changes in the structure and spectral optical properties of glass ceramics with respect to initial glasses were determined by using X-ray diffraction analysis and by studying the luminescent characteristics of dopant ions. 相似文献
5.
O. B. Petrova T. S. Sevostjanova M. O. Anurova A. V. Khomyakov 《Optics and Spectroscopy》2016,120(2):260-267
Lead?barium fluoroborate glasses in the PbF2–BaF2–B2O3, PbF2–BaO–B2O3, and PbO– BaF2–B2O3 systems doped with rare-earth ions (Nd3+ or Er3+) are synthesized and studied. It is shown that, based on these glasses, it is possible to produce transparent glass ceramics with fluoride crystalline phases, including ceramics with one crystalline phase of the fluorite structure. The spectral and luminescent properties of the doped glasses, glass ceramics, and polycrystalline complex fluorides containing Pb, Ba, and rare ions are studied. 相似文献
6.
J. J. Velázquez V. D. Rodríguez A. C. Yanes J. del Castillo J. Méndez-Ramos 《Applied physics. B, Lasers and optics》2012,108(3):577-583
95SiO2?C5LaF3 sol-gel derived nano-glass-ceramics single doped with Eu3+ or Sm3+ and codoped with both of them were successfully obtained. XRD measurements confirm the precipitation of LaF3 nanocrystals after the ceramming process, with mean size ranging from 10 to 20?nm which increases with the thermal treatment temperature. The incorporation of rare-earth ions into precipitated LaF3 nanocrystals was confirmed from luminescence spectra. Intense yellow-red emissions were detected under UV and blue light excitation in single and codoped samples. The effect of codoping with Eu3+ and Sm3+ ions and the energy transfer mechanism between them have been analyzed in order to increase the yellow-red emissions. 相似文献
7.
Ultraviolet, visible and infrared spectral measurements were used to investigate prepared undoped and rare-earth doped (2.5%) bismuth silicate glasses (80% Bi2O3–20%SiO2) before and after being subjected to gamma irradiation (8?Mrad). The base bismuth silicate glass reveals strong extended UV–near visible absorption bands which are attributed to the presence of trace iron impurities in the raw materials together with absorption due to sharing of Bi3+ ions. The RE-doped samples show the same strong UV–near visible bands as the undoped glasses beside extra narrow characteristic bands mostly in the visible and near-infrared regions due to the respective studied rare-earth ions. The base undoped and all RE-doped samples except CeO2 sample reveal quite resistance to the effect of gamma irradiation due to heavy atomic mass Bi3+ ions present in high content (80%) and the rare-earth ions are known to be weakly affected due to the known 5s, 5p shielding. The exceptional effect of CeO2-doped sample is related to the ability of Ce3+ ions to change its oxidation state through photochemical reaction by irradiation or exchange with Fe3+ present as trace iron impurities. The FT infrared spectra of the prepared glasses reveal characteristic absorption bands which are related to the silicate groups together with the sharing of vibrational modes due to Bi–O groups. The IR spectra are slightly affected by gamma irradiation indicating the stability of the structural network groups consisting of SiO4 and BiO6 units. 相似文献
8.
A. C. Yanes J. Méndez-Ramos J. del-Castillo J. J. Velázquez V. D. Rodríguez 《Applied physics. B, Lasers and optics》2010,101(4):849-854
Sol-gel glasses with composition (100?x)SiO2–xSnO2 doped with 0.4 mol% of Sm3+, with x ranging from 1 to 10, have been successfully synthesized. Transparent doped nano-glass-ceramics were prepared by thermal treatment of the precursor glasses at 900°C during 4 hours, leading to nanocomposites comprising SnO2 nanocrystals embedded into an amorphous SiO2 phase. A structural analysis in terms of X-ray Diffraction and High Resolution Transmission Electron Microscopy confirms the precipitation of SnO2 nanocrystals within the glassy matrix. The mean radius of the obtained SnO2 nanocrystals, ranging from 2.1 to 4.7 nm calculated by the Scherrer and Brus equations, similar to the Bohr’s exciton radius, constitutes a wide band-gap semiconductor quantum-dot system. Energy transfer from SnO2 nanocrystal host to Sm3+ ions is confirmed by luminescence spectra and analyzed as a function of SnO2 concentration, showing an evolution that could be ascribed to selective excitation of nanocrystal sets with predetermined size. Besides, a study of the luminescence as a function of temperature helps to clarify the involved energy transfer mechanisms. 相似文献
9.
D. Kowalska P. Haro-González I. R. Martín J. M. Cáceres 《Applied Physics A: Materials Science & Processing》2010,99(4):771-776
This paper reports the results obtained in strontium barium niobate (SBN) nanocrystals in glasses doped with 1, 2.5 and 5 mol%
of Er3+ ions. The melt-quenching method was applied to fabricate the glasses with composition SrO–BaO–Nb2O5–B2O3 and further thermal treatment was used to obtain glass ceramic samples from the glass precursor. X-ray diffraction patterns
confirmed the formation of SBN nanocrystals with an average size of about 50 nm in diameter. Time-resolved fluorescence spectra
for the emission of Er3+ ions at 1550 nm have been analyzed in order to confirm the incorporation of the Er3+ ions into the nanocrystals. Green frequency upconversion emission under excitation at 975 nm coming from the ions in the
nanocrystals has been obtained. This intense upconversion is about a factor of 500 higher than that obtained from the ions
which reside in the glassy phase. Moreover, temporal evolution studies have been carried out with the purpose of determining
the involved upconversion mechanism and the importance of these processes as a source of losses for the optical amplification
at 1550 nm. 相似文献
10.
Rare-earth doped YF3 nanocrystals embedded in sol–gel silica glass matrix for white light generation
J. Méndez-Ramos A. Santana-Alonso A.C. Yanes J. del-Castillo V.D. Rodríguez 《Journal of luminescence》2010,130(12):2508-2511
YF3 nanocrystals triply-doped with Yb3+, Ho3+ and Tm3+ ions embedded in amorphous silica matrix have been successfully obtained by heat treatment of precursor sol–gel glasses for the first time to our knowledge and confirmed by X-ray diffraction and luminescence measurements. Simultaneous UV and visible efficient up-conversion emissions, with well-resolved Stark structure, under 980 nm infrared pump are observed, indicating the effective partition of rare-earth ions into a crystalline-like environment of the YF3 nanocrystals. Corresponding energy transfer mechanisms have been analyzed and overall colour emission has been quantified in terms of standard chromaticity diagram. By an adequate doping level and heat treatment temperature of precursor sol–gel glasses, a bright white colour has been accomplished, close to the standard equal energy white light illumination point, with potential applications in photo-electronic devices and information processing. 相似文献
11.
Rare-earth doped borate glasses and glass ceramics are investigated for their potential as photon converters. Thermal processing of the as-made glass results in the formation of nanocrystals therein. For optical activation, the glasses are doped with Eu3+ and Tb3+, both enabling an intense emission under ultraviolet excitation. Differential scanning calorimetry and X-ray diffraction are applied to analyze the crystallization behavior. Compared to the undoped glass, the glass transition temperature as well as the crystallization temperature are increased with Eu3+ doping. Upon thermal processing of the as-made glasses, the transmittance is significantly reduced. Preliminary photoluminescence quantum efficiency measurements yield lower values for the glass ceramics. 相似文献
12.
P. Yang C.F. Song M.K. Lü G.J. Zhou D. Xu D.R. Yuan 《Applied Physics A: Materials Science & Processing》2002,74(5):689-692
Mg2+-, Ca2+-, Sr2+- and Ba2+-doped silica glasses have been prepared using sol-gel processing by employing Si(OC2H5)4, MgCl26H2O, CaCl22H2O, SrCl26H2O and BaCl22H2O as precursors, with HCl as a catalyst. The UV–visibleabsorption spectra of the doped samples are almost the same as those
of the undoped sample. The absorption bands of alkaline earth metallic ions have not been observed in the doped samples. Strong
visible light has been observed from sol- gel silica glasses doped with alkaline earth metallic ions. The relative fluorescence
intensity of the Sr2+-doped (the impurity mole ratio of Sr2+ was 0.268%) and the Ba2+-doped (the impurity mole ratio of Ba2+ was 0.448%) samples was about 4 times that of the undoped sample. The relative fluorescence intensity of the Mg2+-doped (the impurity mole ratio of Mg2+ was 0.069%) sample was about 2.5 times that of the pure glass sample. The relative fluorescence intensity of the Ca2+- doped (the impurity mole ratio of Ca2+ was 0.179%) sample was about 3 times that of the pure glass sample. Alkaline earth metallic ions affect the formation and
conversion of luminescent defects in sol-gel silica glass. Thus, the relative fluorescence intensity of the doped samples
increases more than that of the undoped sample.
Received: 17 April 2001 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献
13.
The MgO-Ga2O3-SiO2 glass-ceramic (GC) containing MgGa2O4 nanocrystals and glasses doped with Eu3+ ions were prepared by the sol-gel method. The down-conversion and up-conversion luminescence (UCL) properties were studied. The results indicated that the relative intensity of f-f transitions of Eu3+ decreased in contrast with that of charge transfer (CT) absorption with the increase in heating temperature. Using a Xe lamp and 800 nm femtosecond (fs) laser excitation, strong red luminescence of Eu3+ in MgO-Ga2O3-SiO2 glasses and GC was observed. 相似文献
14.
A. C. Yanes A. Santana-Alonso J. Méndez-Ramos J. del-Castillo 《Applied physics. B, Lasers and optics》2013,113(4):589-596
Transparent nano-glass-ceramics containing KYF4 nanocrystals were successfully obtained by the sol–gel method, doped with Eu3+ and co-doped with Yb3+ and Tm3+ ions. Precipitation of cubic KYF4 nanocrystals was confirmed by X-ray diffraction and high-resolution transmission electron microscope images. Excitation and emission spectra let us to discern between ions into KYF4 nanocrystals and those remaining in a glassy environment, supplemented with time-resolved photoluminescence decays, that also clearly reveal differences between local environments. Unusual high-energy up-conversion emissions in the UV range were obtained in Yb3+–Tm3+ co-doped samples, and involved mechanisms were discussed. The intensity of these high-energy emissions was analyzed as a function of Yb3+ concentration, heat treatment temperature of precursor sol–gel glasses and pump power, determining the optimum values for potential optical applications as highly efficient UV up-conversion materials in UV solid-state lasers. 相似文献
15.
A. S. Shcheulin A. E. Angervaks T. S. Semenova L. F. Koryakina M. A. Petrova P. P. Fedorov V. M. Reiterov E. A. Garibin A. I. Ryskin 《Applied physics. B, Lasers and optics》2013,111(4):551-557
When growing CaF2 crystal doped with rare-earth ions, most of these ions are present in a trivalent state. However, due to contact with graphite crucible, a small proportion of a number of ions (Eu, Sm, Yb and Tm) are reduced to a bivalent state. A similar situation takes place during fabrication of CaF2 ceramics doped with rare-earth metals. This fact is of particular importance for laser CaF2:Yb crystals (ceramics), a promising material for short-pulse, high-power, high-energy diode-pumped solid state lasers since the presence of bivalent Yb ions can be a source of thermal losses. To date, there has been no technique to determine Yb2+ concentration in as-grown crystals. The proposed technique is based on a total reduction of Yb3+ ions via the heating of as-grown CaF2 crystals with known concentration of Yb in the reducing atmosphere of metal vapour and determining the cross section of absorption bands of Yb2+ ions. The knowledge of these parameters allows estimation of the Yb2+ content in CaF2:Yb crystals or ceramics by analysing their absorption spectra. Examples of using this technique are given. The technology of CdF2 crystals reduction (an “additive colouring”) and features of colouring of crystals doped with rare-earth ions are considered. 相似文献
16.
Diego S. da Silva Luz P. Naranjo Luciana R. P. Kassab Cid B. de Araújo 《Applied physics. B, Lasers and optics》2012,106(4):1015-1018
We report the first observation of photoluminescence enhancement in Er3+ doped GeO2–Bi2O3 glasses containing silicon nanocrystals (Si-NCs) excited by a laser operating at 980 nm. The growth of ≈200% in the intensity
of the Er3+ transition 4S3/2→4I15/2 (545 nm) and of ≈100% for transitions 2H11/2→4I15/2 (525 nm), 4F9/2→4I15/2 (660 nm), and 4I5/2→4I13/2 (1530 nm) was observed in comparison with a reference sample that does not contain Si-NCs. The results open a new road for
obtaining efficient Stokes and anti-Stokes emissions in germanate composites doped with rare-earth ions. 相似文献
17.
Paramita Saha Chowdhury 《Solid State Communications》2004,131(12):785-788
The emission intensity of the peak at 612 nm (5D0→7F2) of the Eu3+ ions activated SnO2 nanocrystals (doped and coated) is found to be sensitive to the nanoenvironment. We have compared the luminescence efficiencies of the nanocrystals of SnO2 doped by Eu2O3 with those of SnO2 coated by Eu2O3 and we found that the intensities are significantly higher in coated nanocrystals. Furthermore, it is clear from luminescence intensity measurements that Eu3+ ions occupy low symmetry sites in the Eu2O3 coated SnO2 nanocrystal. The analysis suggests that the radiative relaxation rate is higher in Eu2O3 coated SnO2 nanocrystals than Eu2O3 doped SnO2 nanocrystals due to the asymmetric environment of Eu3+ ions in coated samples. 相似文献
18.
Strong temperature controlled segregation of doped ions in Y2SiO5:Pr3+ nanocrystals detected by spectroscopic techniques is reported. The elastic interactions stimulate Pr3+ segregation thus leading to non-uniform distribution of doped ions, pair formation and, as a consequence, to abnormal low threshold of luminescence concentration quenching for Y2SiO5:Pr3+ nanocrystals. 相似文献
19.
Nanocrystalline NiFe2O4 was in‐situ prepared in amorphous silica using tetramethylor‐thosilicate and nickel (iron) nitrate hydrate as the starting materials in a sol‐gel reaction. The magnetic nanocrystals in the amorphous silica glasses grew slowly with increasing temperature. Above 600○C, nickel ferrite nanoparticles began to precipitate from the amorphous silica matrix. Mössbauer spectroscopy of the nanocomposites suggested that in the silica glasses, Fe ions were present exclusively as Fe3+ in octahedral coordination, and the chemical environment of the Fe3+ ions appeared to remain unchanged until the crystallization of nickel ferrite nanocrystals. The formation of NiFe2O4 nanocrystals was the result of partial transformation of the FeO6 octahedra to FeO4 tetrahedra. The nanocrystalline NiFe2O4 are characterized by super‐paramagnetic behaviour at room temperature. 相似文献
20.
Jing Ren Tomas Wagner Jiri Orava Miloslav Frumar 《Journal of Physics and Chemistry of Solids》2010,71(1):30-34
The infrared emission properties of rare-earth (i.e., Dy3+, Pr3+ or Sm3+) and nickel-codoped Ge-Ga-Sb-S glasses were investigated by photoluminescence measurements. It was found that the emission intensities of the rare-earth doped glasses were significantly weakened even with very few amount of nickel (i.e., 500 at. ppm). On the other hand, the nickel-doped glasses show larger indices of refraction, which property will be desirable in nonlinear optics. Our results, however, suggest that to obtain rare-earth doped chalcogenide glasses of better infrared emission property it is necessary to keep the nickel dopant as low as possible. 相似文献