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  • 1
    Electronic Resource
    Electronic Resource
    Insulating Properties of Lanthanum-Doped BaTiO3 Ceramics Prepared by Low-Temperature Synthesis (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 87 (2004), 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: Samples of composition Ba1−xLaxTi1−x/4O3, x= 0, 0.003, 0.03, and 0.10, were prepared by an alkoxide sol–gel route with final firing of ceramics at 1100°C, 2 h in air. All samples showed bulk insulating behavior with no evidence of semiconductivity caused by either direct donor doping or oxygen loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2004.tb06370.x
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical and structural characteristics of lanthanum-doped barium titanate ceramics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6355-6366 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single phase La-doped BaTiO3 with the formula Ba1−xLaxTi1−x/4O3: 0≤x≤0.20 was prepared by solid state reaction of oxide mixtures at 1350 °C, 3 days, in O2. The tetragonal distortion in undoped BaTiO3 decreased with x and samples were cubic for x≥0.05. Both the tetragonal/cubic and orthorhombic/tetragonal transition temperatures decreased with x, but at different rates, and appeared to coalesce at x∼0.08. The value of the permittivity maximum at the tetragonal/cubic phase transition in ceramic samples increased from ∼10 000 for x=0 at 130 °C to ∼25 000 for x=0.06 at ∼−9 °C. At larger x, the permittivity maximum broadened, showed "relaxor"-type frequency dependent permittivity characteristics and continued to move to lower temperatures. Samples fired in O2 were insulating and showed no signs of donor doping whereas air-fired samples were semiconducting, attributable to oxygen loss. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371698
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  • 3
    Electronic Resource
    Electronic Resource
    CaCu3Ti4O12: One-step internal barrier layer capacitor (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2153-2155 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: There has been much recent interest in a so-called "giant-dielectric phenomenon" displayed by an unusual cubic perovskite-type material, CaCu3Ti4O12; however, the origin of the high permittivity has been unclear [M. A. Subramanian, L. Dong, N. Duan, B. A. Reisner, and A. W. Sleight, J. Solid State Chem. 151, 323 (2000); C. C. Homes, T. Vogt, S. M. Shapiro, S. Wakimoto, and A. P. Ramirez, Science 293, 673 (2001); A. P. Ramirez, M. A. Subramanian, M. Gardel, G. Blumberg, D. Li, T. Vogt, and S. M. Shapiro, Solid State Commun. 115, 217 (2000)]. Impedance spectroscopy on CaCu3Ti4O12 ceramics demonstrates that they are electrically heterogeneous and consist of semiconducting grains with insulating grain boundaries. The giant-dielectric phenomenon is therefore attributed to a grain boundary (internal) barrier layer capacitance (IBLC) instead of an intrinsic property associated with the crystal structure. This barrier layer electrical microstructure with effective permittivity values in excess of 10 000 can be fabricated by single-step processing in air at ∼1100 °C. CaCu3Ti4O12 is an attractive option to the currently used BaTiO3-based materials which require complex, multistage processing routes to produce IBLCs of similar capacity. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1463211
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  • 4
    Electronic Resource
    Electronic Resource
    An Alternative Explanation for the Origin of the Resistivity Anomaly in La-Doped BaTiO3 (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: Semiconductivity in La-doped BaTiO3 ceramics after high-temperature firing, e.g., 1350°C in air, is attributed to oxygen nonstoichiometry. In more heavily doped compositions, the observed resistivity rise is attributed to surface oxidation of the grains during cooling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00684.x
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of Lanthanum-Doped Barium Titanate Ceramics Using Impedance Spectroscopy (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 electrical properties of two single-phase, lanthanum-doped BaTiO3 compositions, x= 0.03 and x= 0.20, in Ba1–xLaxTi1–x/4O3 were investigated by impedance spectroscopy after heat treatment in oxygen, argon, and air at 1350°C. Samples heated in oxygen were electrically insulating, whereas those heated in argon lost oxygen and were semiconducting at room temperature, irrespective of x. Samples heated in air showed intermediate electrical properties and also were electrically inhomogeneous; the two compositions showed different electrical behaviors, and a model for each, based on oxygen nonstoichiometry within the ceramics, is proposed. Oxygen deficiency in samples sintered in air was avoided by heating at 1200°C, instead of 1350°C. Alternatively, oxygen lost from ceramics heated in air at 1350°C was regained by postannealing in oxygen at 1350°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00694.x
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  • 6
    Electronic Resource
    Electronic Resource
    Novel Doping Mechanism for Very-High-Permittivity Barium Titanate Ceramics (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), 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: Barium titanate (BaTiO3) can be doped with La3+ ions via partial substitution for Ba2+ ions; charge balance is maintained by the creation of Ti4+ vacancies. Samples processed in an atmosphere of 1 bar O2 and a temperature of 1350°C are insulating and free from electronic defects associated with either O2 loss or reduction of Ti4+ to Ti3+. The Curie temperature (Tc) decreases approximately linearly as the lanthanum content increases and, at the same time, an increase in the permittivity (ɛ′) maximum at Tc occurs. For the composition Ba1-xLaxTi1-x/4O3, where x= 0.05, ɛ′ has a maximum value of 19000 at 18°C, compared with a typical value of 10000 at 130°C in undoped BaTiO3 ceramics. This value is the highest value reported for A-site-doped BaTiO3 and is linked to the mechanism of combined A-site doping and Ti-vacancy creation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02575.x
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  • 7
    Electronic Resource
    Electronic Resource
    Polymorphism and Thermodynamic Stability of Zn7Sb2O12 (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 composition Zn2.33Sb0.67O4 (or Zn7Sb2O12) exists in two polymorphic forms. The thermodynamically stable, low-temperature orthorhombic β form transforms to the high-temperature cubic α-polymorph with a spinel structure at 1225°±25°C. The transformation is fully reversible but slower in the α→β direction and therefore, it is easy to preserve the high-temperature α-polymorph to lower temperatures where it is kinetically stable but thermodynamically metastable. It is also possible to synthesize the α-polymorph directly at low temperatures, e.g., 900°C. This synthesis, of a phase that is thermodynamically stable only at high temperatures, but which has sufficient kinetic stability to exist metastably at low temperatures, represents an example of Ostwald's law of successive reactions in which the first phase to crystallize from a reaction mixture is not necessarily the equilibrium phase of lowest free energy. The crystal structure of the α-polymorph has been confirmed by Rietveld refinement of X-ray powder diffraction data to be an inverse spinel, (Zn)[Sb2/3Zn4/3]O4, in which octahedral sites contain a disordered, random mixture of Zn and Sb and tetrahedral sites are fully occupied by Zn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00047.x
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  • 8
    Electronic Resource
    Electronic Resource
    Electroceramics: Characterization by Impedance Spectroscopy (1990)
    Weinheim : Wiley-Blackwell
    Advanced Materials 2 (1990), S. 132-138 
    Details
    ISSN: 0935-9648
    Keywords: Ferroelectric Ceramics ; Grain Boundary Capacitances ; Ceramic Electrolytes ; Surface Layers on Glasses ; Ferromagnetic Ceramics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Electroceramics are advanced materials whose properties and applications depend on the close control of structure, composition, ceramic texture, dopants and dopant (or defect) distribution. Impedance spectroscopy is a powerful technique for unravelling the complexities of such materials, which functions by utilizing the different frequency dependences of the constituent components for their separation. Thus, electrical inhomogeneities in ceramic electrolytes, electrode/electrolyte interfaces, surface layers on glasses, ferroelectricity, positive temperature coefficient of resistance behavior and even ferrimagnetism can all be probed, successfully, using this technique.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19900020304
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  • 9
    Electronic Resource
    Electronic Resource
    A.C. impedance of surface layers and blocking electrodes on single crystal ß-alumina (1982)
    Springer
    Journal of materials science 1 (1982), S. 522-524 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00724736
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of Electrical Materials, Especially Ferroelectrics, by Impedance Spectroscopy (1997)
    Springer
    Journal of electroceramics 1 (1997), S. 65-71 
    Details
    ISSN: 1573-8663
    Keywords: impedance data ; equivalent circuits ; ferroelectric materials ; impedance and modulus spectroscopy ; lithium tantalate ferroelectric ; barium titanate
    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 A review is given of some of the problems encountered in the analysis and interpretation of impedance data. The importance of choosing the correct equivalent circuit to represent the data is emphasized and it is shown how ferroelectric materials, with their characteristic temperature-dependent capacitance, are particularly suited to discriminating between plausible equivalent circuits. Results are discussed for two materials, LiTaO3 single crystal and BaTiO3 ceramics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009950415758
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