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  • 1
    Digitale Medien
    Digitale Medien
    Structural Study on PbO–SiO2 Glasses by X-Ray and Neutron Diffraction and 29Si MAS NMR Measurements (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Structure of xPbO–(100−x)SiO2 (x=25–89) glasses has been investigated by means of the X-ray and neutron diffraction and 29Si MAS NMR measurements. In the radial distribution functions of all the glasses, the Pb–O correlation was observed at 0.23 nm, indicating that the PbO3 trigonal pyramids units do exist in the whole glass forming composition range. Furthermore the existence of the first Pb–Pb correlation at ∼0.385 nm in the whole composition range suggests that the basic structural unit is considered to be a Pb2O4 unit, which consists of the edge-shared PbO3 trigonal pyramids. These results strongly imply that the Pb2O4 units participate in the glass network constructed by SiO4 tetrahedra even at low PbO content. Differing from other lead-containing glass systems, these structural characteristics of Pb ions in the PbO–SiO2 glass system are responsible for the extremely wide glass-forming region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00297.x
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  • 2
    Digitale Medien
    Digitale Medien
    Ultraviolet-photosensitive effect of sol–gel-derived GeO2–SiO2 glasses (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3413-3418 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Germanosilicate glasses are prepared by a sol–gel method and the ultraviolet (UV) photosensitivity of the glasses is investigated by optical absorption, electron spin resonance, and photoluminescence measurements. A KrF pulsed laser and a Hg lamp are used as UV light sources. The concentrations of intrinsic germanium-related oxygen-deficient centers in the glasses are successfully controlled by sintering conditions; in air or under reduced pressure. One-order larger intensity of the 5 eV absorption band is observed in the sol–gel glass sintered under the latter condition, as compared to a fiber preform of almost the same composition, which is formed by the vapor-phase axial deposition method. The effect of irradiation with KrF laser pulses on sol–gel glass is different from that on preform glass. On the other hand, the Hg-lamp illumination has the same effect on both sol–gel glass and preform glass. Based on these results, we discuss the defect states in sol–gel-derived glass and fiber preform glass and also the mechanisms of photochemical reactions under these two UV light sources. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.369698
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  • 3
    Digitale Medien
    Digitale Medien
    Upconversion luminescence of Er3+ in CdX2 system glasses (X=Cl, Br, I) (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2453-2455 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Near-infrared to visible upconversion characteristics of Er3+ in CdX2-based halide glasses (X=Cl, Br, or I) has been investigated. When 4I9/2 state is pumped by 800 nm radiation from an AlGaAs laser diode, the upconverted green emissions (520–560 nm) of 2H11/2+4S3/2→I15/2 transition are clearly observed in all the glasses. The linewidth of green emission in these glasses becomes narrow in the order of chloride, bromide, and iodide. The CdCl2 and CdBr2 system glasses give blue upconversion luminescence (around 410 nm) due to the 2H9/2→I15/2 transition, but this emission is not observed in the CdI2 system glass because of the absorption edge at around 450 nm. The fluorescence spectra of CdX2 system glasses suggest that the multiphonon relaxation rate depends on choice of the X species. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.114605
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  • 4
    Digitale Medien
    Digitale Medien
    Up-conversion characteristics of Er3+ in transparent oxyfluoride glass–ceramics (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3920-3922 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Up-conversion characteristics of Er3+ under 800 nm excitation are clarified for 30SiO2 ⋅15AlO1.5⋅28PbF2⋅22CdF2⋅(5−x)GdF3⋅xErF3 (x=0.3–5) transparent glass–ceramics, which are composed of fluoride nanocrystals and oxide glass matrices. Strong up-conversion emissions at around 525, 550, and 660 nm, and weak up-conversion emissions at around 410, 450, and 490 nm are observed. The intensities of up-conversion emissions at around 550 and 660 nm change remarkably with ErF3 contents from 1 mol % to 5 mol %: emission at 550 nm decreases and one at 660 nm increases with increasing ErF3 content. These features can be explained by Er3+ up-conversion mechanisms which were proposed for ZrF4-based glasses. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.367140
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  • 5
    Digitale Medien
    Digitale Medien
    Thermal equilibrium of Ge-related defects in a GeO2-SiO2 glass (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1287-1289 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In a 15.7 GeO2⋅84.3 SiO2 glass prepared by a vapor axial deposition method, optical absorptions at 4.92 and 5.08 eV were observed from 300 to 600 K. The results were then compared with electron spin resonance (ESR) measurement using the same samples. The absorption at 4.92 eV was found to increase with increasing temperature, while the optical absorption at 5.08 eV decreased with increasing temperature. These changes of optical absorption indicate that the concentration of neutral oxygen monovacancy is reduced at higher temperatures. The changes were quite reversible with the temperature. Concentration of Ge E′ center, estimated from ESR, increased with increasing temperature, which is in contrast with the decrease of neutral oxygen monovacancy. The present result strongly suggests the thermal equilibrium reaction between neutral oxygen monovacancy and Ge E′ center. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.121052
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  • 6
    Digitale Medien
    Digitale Medien
    Second-harmonic generation in germanosilicate glass poled with ArF laser irradiation (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1032-1034 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on a remarkably large second-harmonic generation (SHG) in a germanosilicate glass (15.7 GeO2–84.3 SiO2 in mol %), which was induced by poling while the sample was irradiated with the ArF laser at the wavelength of 193 nm. The SHG coefficient, d, thus induced was measured at various poling electric-field strengths using the Maker-fringe technique. The value of d increases with increasing poling field and then saturates around 1.5×105 V/cm. The largest d coefficient value obtained in this work, which is 3.4±0.3 pm/V, seems to exceed d22 of LiNbO3. Furthermore, polarization dependence of the induced SHG shows an anisotropy of the refractive index. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.119718
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  • 7
    Digitale Medien
    Digitale Medien
    Upconversion luminescence of Er3+ in chloride glasses based on ZnCl2 or CdCl2 (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1874-1876 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Upconversion luminescence of Er3+ in the chloride glass system has been investigated in ZnCl2-BaCl2-KCl-ErCl3 and CdCl2-BaCl2-KCl-ErCl3 glasses. Under 800 nm excitation, the glasses gave upconversion luminescence with barely detectable red (around 660 nm), very intense green (around 525–560 nm), and considerably intense blue (around 410 nm) emissions. The intensity of blue emissions was far stronger than that observed for any of other Er3+-doped glass systems, revealing that Er3+-doped chloride glasses can efficiently convert the infrared light into much shorter wavelengths. The green emission is attributed not only to the thermally coupled 2H11/2 and 4S3/2→4I15/2 transition but also to the 2H9/2→4I13/2 transition. The blue emission is due to the 2H9/2→4I15/2 transition. The blue and green upconversion luminescence results from a two-photon process. © 1994 American Institue of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.112874
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  • 8
    Digitale Medien
    Digitale Medien
    Correlation between Macro- and Microstructural Changes in Ge:SiO2 and SiO2 Glasses under Intense Ultraviolet Irradiation (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: The photochemical transformation mechanism of defects in germanosilicate and silica glasses under ultraviolet (UV) laser irradiation has been investigated based on the changes in Raman spectra before and after irradiation. Two types of silica glasses, fused silica (type I) and dry synthetic silica (type IV), and germanosilicate optical fiber preforms were irradiated by intense UV photons from excimer lasers. Spectral changes in optical absorption and Raman spectra were examined to clarify a correlation between the microscopic defect formation and the macroscopic structural changes causing a photorefractive effect. Successive generation of E′ centers through divalent centers is closely correlated with changes in Raman spectra, indicating that large structural changes in the glass network involved in this process would be the origin of photon-induced densification of the glasses. In addition, it has been proposed that the successive generation of E′ centers is mediated by transient divalent centers converted from relaxed cation homobondings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00227.x
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  • 9
    Digitale Medien
    Digitale Medien
    Leaching of Lead and Connectivity of Plumbate Networks in Lead Silicate Glasses (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: The formation of a plumbate network in binary lead silicate glasses was examined based on the leaching behavior of Pb2+ in lead silicate glasses over a wide composition region. The effective diffusion coefficient of Pb2+ at 40°C was on the order of 10−17 m2/s for PbO〈35 mol% glasses, and increased three orders of magnitude for 35–50 mol% PbO contents. Such a steep composition dependence is considered to be because of changes in the medium or longer range structure. That is, it is proposed that the plumbate network forms a percolative 3D network in the composition region to form diffusion paths for the lead ions. In addition, the present results indicate that the lead ion exists as a network former over the entire glass forming composition range of the binary silicate glasses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00508.x
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  • 10
    Digitale Medien
    Digitale Medien
    Preparation, Structure, and Properties of Thermally and Mechanically Improved Aluminum Titanate Ceramics Doped with Alkali Feldspar (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Aluminum titanate (AT) ceramic materials doped with alkali feldspar ((Na0.6K0.4)AlSi3O8) have been prepared. These ceramics exhibited high sinterability, large resistance to thermal decomposition, and large flexure strength. The existence of liquid-phase feldspar at sintering temperatures promoted the formation of AT ceramics as the sintering agent. It was considered that silicon ions substituting for aluminum ions at the surface of AT crystal grains lowered the surface energy and hindered the diffusion of Ti4+ and Al3+, giving rise to the large resistance to thermal decomposition. As a result, doping with alkali feldspar was found to effectively improve the mechanical and thermal properties of AT ceramics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00573.x
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