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  • 2005-2009
  • 2000-2004  (2)
  • 1995-1999  (7)
  • 2002  (2)
  • 1999  (4)
  • 1997  (3)
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  • 2005-2009
  • 2000-2004  (2)
  • 1995-1999  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the admittance-frequency and capacitance–voltage of dense SnO2⋅CoO-based varistor ceramics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 6007-6014 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes the admittance-frequency feature of a class of SnO2⋅CoO-based polycrystalline ceramics with high nonlinear current–voltage characteristics (nonlinear coefficients above 50). Broad relaxation peaks caused by the presence of deep trap states were characterized based on the admittance response of different systems doped with La2O3, Pr2O3, and CeO2. The calculation of the energy of this deep trap level revealed not only that all the compositions share the same value but also that this value could be attributed to an oxygen vacancy or to CoSn[partial lengthening] like defects. The values of barrier height and density of states obtained from a capacitance–voltage analysis are in good agreement with the nonlinear coefficients. The highest nonlinear coefficients are found in compositions with greater barrier height values and higher density of deep trap states at the grain boundary interface. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1455685
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  • 2
    Electronic Resource
    Electronic Resource
    Ferroelectric and optical properties of Ba0.8Sr0.2TiO3 thin film (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5972-5978 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Barium strontium titanate (Ba0.8Sr0.2TiO3) thin films have been prepared on Pt/Ti/SiO2/Si substrates using a soft solution processing. X-ray diffraction and also micro-Raman spectroscopy showed that the Ba0.8Sr0.2TiO3 thin films exhibited a tetragonal structure at room temperature. The presence of Raman active modes was clearly shown at the 299 and 725 cm−1 peaks. The tetragonal-to-cubic phase transition in the Ba0.8Sr0.2TiO3 thin films is broadened, and suppressed at about 35 °C, with a maximum dielectric constant of 948 (100 kHz). Electrical measurements for the prepared Ba0.8Sr0.2TiO3 thin films showed a remnant polarization (Pr) of 6.5 μC/cm2, a coercive field (Ec) of 41 kV/cm, and good insulating properties. The dispersion of the refractive index is interpreted in terms of a single electronic oscillator at 6.97 eV. The direct band gap energy (Eg) and the refractive index (n) are estimated to be 3.3 eV and n = 2.27–2.10, respectively. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1466526
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  • 3
    Electronic Resource
    Electronic Resource
    Thickness dependence of leakage current in BaBi2Ta2O9 thin films (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 552-554 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: BaBi2Ta2O9 thin films having a layered structure were fabricated by metalorganic solution deposition technique. The films exhibited good structural, dielectric, and insulating properties. The room temperature resistivity was found to be in the range of 1012–1014 Ω cm up to 4 V corresponding to a field of 200 kV/cm across the capacitor for films annealed in the temperature range of 500–700 °C. The current-voltage (I–V) characteristics as a function of thickness for films annealed at 700 °C for 1 h, indicated bulk limited conduction and the log(I) vs V1/2 characteristics suggested a space-charge-limited conduction mechanism. The capacitance–voltage measurements on films in a metal–insulator–semiconductor configuration indicated good Si/BaBi2Ta2O9 interface characteristics and a SiO2 thickness of ∼5 nm was measured and calculated. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124419
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of sintering process and atmosphere on the non-ohmic properties of SnO2 based varistor (1999)
    Springer
    Journal of materials science 10 (1999), S. 321-327 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The non-ohmic properties of the 98.95% SnO2 + 1.0%,CoO + 0.05%,Nb2O5 (all in mole%) system, as well as the influence of sintering temperature and atmosphere on these properties, were characterized in this study. The maximum non-linear coefficient (α = 32) was obtained for a sintering temperature of 1300°C in an oxygen atmosphere and this maximum is associated with the presence of O in SnO2 grain boundaries, as interface defects. Experimental results also indicate thermionic-type conduction mechanisms, which are associated with the potential barrier of Schottky or Poole–Frenkel types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008933004042
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  • 5
    Electronic Resource
    Electronic Resource
    Piezoelectric behaviour of PZT doped with calcium: a combined experimental and theoretical study (1997)
    Springer
    Journal of materials science 32 (1997), S. 2381-2386 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental and theoretical study on the piezoelectric behaviour of PZT doped with a range of calcium ion concentrations is presented. A systematic study of the effect on the piezoelectric properties of PZT doped with various concentrations of CaO at constant sintering temperature and sintering time was carried out. The remanent polarization, planar coupling factor and frequency–thickness constant increase with calcium concentration. Ab initio perturbed ion calculations show that the lattice energy decreases with calcium addition for both tetragonal and rhombohedral phases of PZT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018501022807
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental and theoretical study on the piezoelectric behavior of barium doped PZT (1999)
    Springer
    Journal of materials science 34 (1999), S. 3659-3667 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental and theoretical study of the ferroelectric and piezoelectric behavior of PZT doped with barium is presented. Ab initio perturbed ion calculations was carried out. The properties, such as remnant polarization, coercive field and the coupling factor of the PZT at constant sintering temperature was compared with the Zr4+/Ti4+ ions dislocation energy and the lattice interaction energy. An agreement between the experimental and theoretical results, with a decrease of the interaction energy and an inversion of the energy stability from tetragonal to rhombohedral phase was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004647204505
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  • 7
    Electronic Resource
    Electronic Resource
    Experimental and theoretical aspects of the stabilization of zirconia. (1999)
    Springer
    Journal of materials science 34 (1999), S. 2751-2756 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Using the Rietveld method, phases of ceria-doped zirconia, calcined at temperatures of 600 and 900 °C, were quantitatively analysed for different concentrations of ceria. The results show that the stabilization of zirconia depends on the dopant concentration and calcination temperature. Moreover, the theoretical calculation using the ab initio Hartree–Fock–Roothaan method indicates that the most stable phases for ceria-stabilized zirconia are cubic or tetragonal, in accordance with experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004698026465
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Bi2O3 addition on the microstructure and electrical properties of the SnO2.CoO.Nb2O5 varistor system (1997)
    Springer
    Journal of materials science 16 (1997), S. 634-638 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Abstracts are not published in this journal
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018515232646
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  • 9
    Electronic Resource
    Electronic Resource
    An ab initio study of oxygen vacancies and doping process of Nb and Cr atoms on TiO2 (110) surface models (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 625-631 
    Details
    ISSN: 0020-7608
    Keywords: ab initio ; oxygen vacancy ; doping ; titanium oxide surface ; varistor ceramics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We theoretically investigated how the formation of oxygen vacancies and the addition of niobium and chromium atoms as dopants modify the varistor properties of TiO2. The calculations were carried out at the HF level using a contracted basis set, developed by Huzinaga et al., to represent the atomic centers on the (110) surface for the large (TiO2)15 cluster model. The change of the values for the net atomic charges and band gap after oxygen vacancy formation and the presence of dopants in the lattice are analyzed and discussed. It is shown that the formation of oxygen vacancies decreases the band gap while an opposite effect is found when dopants are located in the reduced surface. The theoretical results are compared with available experimental data. A plausible explanation of the varistor behavior of this system is proposed.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 625-631, 1997
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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