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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 31 (Nov. 2007), p. 117-119 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Convective self-assembly of colloidal spheres provides a simple method for fabricatingtwo and three dimensional colloidal crystals. In this work, we investigated the layer transitionsphenomena during colloidal self-assembly in a sessile drop by using an in-situ videoscopic set-up.The effects of surface charge, colloidal concentration, and surfactant additions were examined. Theresults show that the chemical environment plays an important role in colloidal self-assembly. Inthe case of ordered growth, different layer transition phenomena were observed when the colloidalconcentration is different
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 207-209 (Feb. 1996), p. 129-132 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5287-5295 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single crystals have been grown in the (Bi1/2Na1/2)1−xBaxZryTi1−yO3 perovskite system by a self-flux method over the range of compositions y=0.04 and x=0.06–0.012. Rhombohedral (x≤0.08) and tetragonal phase (x≥0.09) crystals have been obtained that do not show polarization or field-induced strain hysteresis characteristics of a ferroelectric. However, a frequency-dispersive dielectric response characteristic of a relaxor ferroelectric, and predominantly electrostrictive actuation, is observed across the range of compositions tested, with Q11=(2.8–3.3)×10−2 m4/C2. Due to induced polarizations that do not saturate at fields beyond 50 kV/cm, high electrostrictive strains are obtained. Rhombohedral phase crystals exhibit d33 up to 1180 pC/N and strains of S3=0.3% before electrical breakdown, while tetragonal phase crystals exhibit d33 up to 2000 pC/N and S3 up to 0.45% strain. These crystals show the highest electrostrictive strains yet reported for an inorganic compound. The unusually high electrostriction is discussed in relation to an energy landscape that allows ferroelastic and ferroelectric distortions to be simultaneously accessible at the nanometer scale. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6902-6909 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-strain active materials often exhibit relaxation in their response to an electric or magnetic field. This phenomenon has been previously described by a loss factor (tangent of the phase shift). However, the loss factor cannot express frequency-dependent, nonperiodic time-dependent, or nonlinear responses, therefore more fundamental material constants are needed. We present a phenomenological model that describes the time- and frequency-dependent behavior of electromechanically (piezoelectric and electrostrictive) and magnetomechanically (magnetic shape memory and magnetostrictive) active materials. Expanding rheology, we introduce electrorheological and magnetorheological models incorporating time constants corresponding not only to the viscoelastic response, i.e., strain versus stress, but also: (1) polarization or magnetization versus field, (2) strain versus polarization or magnetization, (3) ferro- and antiferroelectric, ferro- and antiferromagnetic, or ferroelastic domain switching under applied field and/or stress. A single set of constitutive equations is obtained that can describe pure and mixed cases of ferroic, antiferroic, and nonferroic response. The simulated behavior agrees well with experimental data for both polycrystalline piezoelectrics and high electromechanical strain single crystals. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7382-7388 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic characterization has been performed on the cubic phases λ-Li0.07Mn2O4, Li0.98Mn2O4, and the tetragonal phase Li1.82Mn2O4, prepared by electrochemical cycling of a single starting LiMn2O4 spinel. The magnitude of the negative Weiss constant increases with x in LixMn2O4, indicating that antiferromagnetic interactions increase in strength as the Mn4+ concentration decreases. Spin-glass behavior is observed in all three materials, as previously seen in nearly stoichiometric LiMn2O4 [Jang et al., Appl. Phys. Lett. 74, 2504 (1999)]. A short-range antiferromagnetic correlation is observed in Li2Mn2O4 at temperatures below the paramagnetic temperature regime, which is ascribed to collective Jahn–Teller distortion causing a two-dimensional nearest-Mn-neighbors interaction. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3683-3685 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Doped alkaline–bismuth–titanate perovskite single crystals have been grown in ferroelectric phases with high piezoelectric actuation. Rhombohedral-phase Na1/2Bi1/2TiO3–BaTiO3 crystals exhibit up to 0.25% free strain with low hysteresis along the cubic 〈001〉 direction (d33∼450 pC/N). Tetragonal phase crystals exhibit free strains as high as 0.85% with greater hysteresis characteristic of domain switching; low field d33 exceeds 500 pC/N. Strain energy densities exceed those of optimized polycrystalline lead perovskites, and actuation capability is retained at compressive stresses 〉100 MPa. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2504-2506 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: LiMn2O4 spinel exhibits spin-glass behavior below 25 K. A cusp in the ac susceptibility appears at 25 K, below which the susceptibility increases with decreasing frequency. The dc magnetization shows irreversibility, and relaxation of remanent magnetization is seen on the macroscopic time scale. The randomness and frustration necessary for spin-glass behavior are explained in a manner compatible with the cation and charge ordering present in this material. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 768-770 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that flux pinning in Bi2(Sr,Ca)3−xCu2O8+δ is increased by intentional deviations in cation nonstoichiometry. Polycrystalline samples of alkaline earth-deficient composition (x=0.24–0.32) show a larger irreversibility in magnetization (ΔM), and a slower decay of ΔM with both increasing field and time than stoichiometric compositions. The difference between compositions grows with increasing field out to 5 T, and is greatest at T≤20 K but still significant at 40 K. The critical state model yields a difference in intragranular current density (Jcm) at 20 K and 2 T of (approximately-greater-than)102 between stoichiometric and x=0.3 compositions. Flux pinning energies determined from relaxation of magnetization are several times greater for cation-deficient than for stoichiometric compositions. These improvements are only achieved upon slow cooling or low-temperature annealing, indicating that defect clustering or incipient precipitation is necessary to form more effective pinning defects.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    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: Activated sintering in Bi2O3-doped ZnO has been studied with emphasis on the mechanistic role of intergranular amorphous films. The atomic-level microstructures and bismuth solute distributions in doped powders have been investigated using high-resolution electron microscopy and scanning transmission electron microscopy. Densification is observed to be significant below the bulk eutectic temperature in the presence of Bi2O3 concentrations as low as 0.58 mol%. Transmission electron microscopy of as-calcined and sintered powders shows that significant neck growth and particle coarsening occur in the solid state. Intergranular amorphous films of ∼1 nm thickness, terminating in wetting menisci at sinter-necks, are observed to form concurrently with the onset of activated sintering. In a few instances, amorphous films are also observed at surfaces of the ZnO particles. These films appear to be the free-surface counterpart to equilibrium-thickness intergranular films. Activated sintering in this binary system is attributed to rapid mass transport through subeutectic, equilibrium-thickness intergranular films, with the amorphous phase also providing capillary pressure.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    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: ZnO additions to BaTiO3 have been studied in order to determine the role of this dopant on sintering and microstructure development. As a consequence of a better initial dopant distribution, samples doped with 0.1 wt% zinc stearate show homogeneous fine-grained microstructure, while a doping level of 0.5 wt% solid ZnO is necessary to reach the same effect. When solid ZnO is used as the dopant precursor, ZnO is redistributed among the BaTiO3 particles during heating. Since no liquid formation has been detected for temperatures below 1400°C in the system BaTiO3-ZnO, it is proposed that dopant redistribution takes place by vapor-phase transport and grain boundary diffusion. Shrinkage and porosimetry measurements have shown that grain growth is inhibited during the first step of sintering for the doped samples. STEM-EDX analysis revealed that solid solubility of ZnO into the BaTiO3 lattice is very low, being strongly segregated at the grain boundaries. Grain growth control is attributed to a decrease in grain boundary mobility due to solute drag. Because of its effectiveness in controlling grain growth, ZnO appears to be an attractive additive for BaTiO3 dielectrics.
    Type of Medium: Electronic Resource
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