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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic and Mössbauer spectral study of mixed valent La0.2Sr0.8Cu0.2Fe0.8O2.68 and related perovskites (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5341-5343 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The La0.2Sr0.8Cu1−xFexO3−δ perovskites are important because they are mixed electron and oxygen anion conductors and thus are able to serve as dense oxygen separation membranes. In order to better understand the mechanism for this separation a Mössbauer spectral study has been carried out to determine the ratio of iron(III) to iron(IV) in these mixed valent compounds. The Mössbauer spectra of La0.2Sr0.8Cu0.2Fe0.8O3−δ obtained between 4.2 and 78 K reveal that its Néel temperature is ∼75 K and the two well-resolved magnetic sextets observed between 4.2 and 45 K indicate the presence of trapped valence iron(III) and iron(IV). At 4.2 K the respective hyperfine fields are 454 and 299 kOe and the isomer shifts are 0.388 and 0.057 mm/s. The iron(III) to iron(IV) ratio is 1.20, a ratio which yields a δ value of 0.32 and, if one assumes the presence of only copper(II), a corresponding stoichiometry of La0.2Sr0.8Cu0.2Fe0.8O2.68. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370246
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  • 2
    Electronic Resource
    Electronic Resource
    Optical properties of undoped and Gd-doped CeO2 nanocrystalline thin films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2308-2314 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of studies of the preparation, structure, and optical properties of undoped and Gd-doped CeO2 thin films are presented. Dense films with 4–150 nm grain size have been obtained on monocrystalline sapphire substrates using a polymeric precursor spin coating method. The results of the optical measurements are presented and correlated with the microstructure of the films. The transmission spectra have been used to determine the energy dependence of the refractive index, n and the extinction coefficient, k. Both n and k of the thin films decreased as grain size decreased and these results showed that this change could be related to the transition from crystalline to amorphous CeO2. The effect of dopant has little influence on n, 〈5%, but doping resulted in about a 30%–40% reduction of k compared to undoped specimens, which could be related to the decrease of absorption centers due to the replacement of Ce by Gd. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1430890
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  • 3
    Electronic Resource
    Electronic Resource
    Electrical Conductivity and Lattice Defects in Nanocrystalline Cerium Oxide Thin Films (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The results of the electrical conductivity and Raman scattering measurements of CeO2 thin films obtained by a polymeric precursor spin-coating technique are presented. The electrical conductivity has been studied as a function of temperature and oxygen activity and correlated with the grain size. When compared with microcrystalline samples, nanocrystalline materials show enhanced electronic conductivity. The transition from extrinsic to intrinsic type of conductivity has been observed as the grain size decreases to 〈100 nm, which appears to be related to a decrease in the enthalpy of oxygen vacancy formation in CeO2. Raman spectroscopy has been used to analyze the crystalline quality as a function of grain size. A direct comparison has been made between the defect concentration calculated from coherence length and nonstoichiometry determined from electrical measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00950.x
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and Microstructural Characterization of Unsupported Nanocrystalline Zirconia Thin Films (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A polymeric precursor spin-coating technique is illustrated in which yttrium-stabilized zirconia (YSZ) thin films are produced on Si, Al2O3, and NaCl at temperatures less than 350°C. High-resolution transmission electron microscopy (HRTEM) examinations show that the YSZ films are nanocrystalline (grain size of less than 5 nm), fully dense, and have a stabilized cubic fluorite structure. Using the polymeric precursor spin coating method, unsupported nanocrystalline thin films of YSZ with thicknesses ranging from 30 to 1000 nm are prepared by transferring the films from a host substrate to metallic TEM grids with unsupported areas exceeding 1 mm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00762.x
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  • 5
    Electronic Resource
    Electronic Resource
    The transport properties of nanocrystalline SrCe0.95Yb0.05O3 thin films (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 4171-4173 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of electrical transport measurements on nanocrystalline SrCe0.95Yb0.05O3 thin films are presented. Dense SrCe0.95Yb0.05O3 thin films with 30–70 nm grain size have been obtained using a spin-coating technique. These films exhibit about 103 higher electrical conductivity when compared with the bulk polycrystalline material. The grain size of thin films is stable to temperatures as high as 1000 °C since no grain-coarsening was observed. These unique electrical properties of nanocrystalline SrCe0.95Yb0.05O3 thin films are attributed to a dominant role of grain boundaries and/or interfaces. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116975
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  • 6
    Electronic Resource
    Electronic Resource
    Band gap energy in nanocrystalline ZrO2:16%Y thin films (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 341-343 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of optical absorption measurements on nanocrystalline ZrO2:16%Y thin films are presented. Dense 0.7 μm thick films with 1–300 nm grain size have been obtained on sapphire substrate using a polymeric precursor spin coating technique. The relationship between the energy gap and microstructure of ZrO2:16%Y has been determined and discussed. The quantum confinement effect was observed at the grain size lower than 100 nm with the band gap energy shift of 0.25 eV when the microstructure was changed up to 1 nm. Some limitation of the model has been observed and discussed. The band gap energy of 5.62±0.05 eV has been determined as microstructure independent value. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123065
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  • 7
    Electronic Resource
    Electronic Resource
    The Optical Properties and Band Gap Energy of Nanocrystalline La0.4Sr0.6TiO3 Thin Films (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effects of microstructure on the optical properties of La0.4Sr0.6TiO3 thin films were investigated. Dense films with the thickness of ∼200 nm and grain size 14–30 nm were produced on monocrystalline sapphire substrates by using a polymeric precursor spin coating technique at annealing temperatures under 800°C. X-ray data showed the formation of a single-phase cubic perovskite-type structure similar to undoped SrTiO3 for annealing temperatures 〉500°C. The results of optical measurements showed that the optical spectra varied with the change of the grain size. From these data, the absorption coefficients were calculated and the band gap energy determined. In agreement with the quantum confinement model, it was shown that the band gap energy increased as the grain size decreased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00216.x
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  • 8
    Electronic Resource
    Electronic Resource
    Defect and Mixed Conductivity in Nanocrystalline Doped Cerium Oxide (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The results obtained from a study on the microstructure and the electrical properties of Gd-doped CeO2 thin films were reported. Dense, nanocrystalline films on sapphire substrates are prepared using a polymeric precursor spin coating technique. The electrical conductivity was studied as a function of temperature and oxygen activity and correlated with the grain size. For nanocrystalline Gd-doped CeO2 thin films, the ionic conductivity increased with decreasing activation energy as the grain size decreased. A conductivity model was developed to analyze PO2 behavior of the electrical conductivity. Using the conductivity model, the hopping energy of electron conduction and the enthalpy of oxygen vacancy formation were determined for different microstructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00302.x
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  • 9
    Electronic Resource
    Electronic Resource
    Raman Spectroscopy of Nanocrystalline Ceria and Zirconia Thin Films (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The results of Raman-scattering studies of nanocrystalline CeO2 and ZrO2:16% Y (YSZ) thin films are presented. The relationship between the lattice disorder and the form of the Raman spectra is discussed and correlated with the microstructure. It is shown that the Raman line shape results from phonon confinement and spatial correlation effects and yields information about the material nonstoichiometry level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00509.x
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  • 10
    Electronic Resource
    Electronic Resource
    Microstructure Development in Unsupported Thin Films (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: To better understand the role of the substrate in the microstructural evolution of thin films, unsupported nanocrystalline yttrium-stabilized zirconia (ZrO2:16%Y or YSZ) films were examined as a function of temperature and annealing time. Grain growth, texturing, and pinhole formation were measured using transmission electron microscopy (TEM) and electron diffraction. Films were produced and subsequently annealed on metallic grids using a previously developed technique that results in near full density films at low annealing temperatures. Microstructural evolution in these films was unique compared with constrained films. Grains were found to spheroidize much more readily, ultimately resulting in the formation of porosity and pinholes. Grain growth was found to stagnate at a size particular to each annealing temperature, presumably due to the effects of Zener pinning. It is proposed that the lack of substrate strain and confinement effects allows for the dominance of surface energetics with respect to microstructural evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00203.x
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