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  • 1
    Online Resource
    Online Resource
    Size and temperature induced phase transition behaviors of barium titanate nanoparticles
    AIP Publishing ; 2006
    In:  Journal of Applied Physics Vol. 99, No. 5 ( 2006-03-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 99, No. 5 ( 2006-03-01)
    Abstract: High density, almost impurity-free and defect-free barium titanate (BaTiO3) fine particles with various sizes from 20to1000nm were prepared by the two-step thermal decomposition of barium titanyl oxalate and postheating treatment. The crystal structures of these particles were investigated as a function of the size and the temperature using synchrotron radiation x-ray diffraction (XRD) measurement. As a result, the size-induced ferroelectric (tetragonal-cubic) phase transition observed at around 30nm. Moreover, the temperature dependence of the crystal structures revealed that one phase transition at 135°C separated into two kinds of phase transition behaviors with decreased particle sizes, i.e., the tetragonal-cubic phase transition temperature was constant at 135°C despite particle sizes while the cell volume expansion temperature shifted to low temperature with decreasing particle sizes. Moreover, the temperature dependence of Raman scattering spectra clarified that the temperature at a discontinuous change of damping factor was almost consisted with the cell volume expansion temperature from the XRD measurement. These results suggested that the phase transition behavior of the BaTiO3 nanoparticles was quite different from that of the BaTiO3 single crystals.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.2179971
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2006
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    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 2
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    Dielectric and optical properties of BaTiO3/SrTiO3 and BaTiO3/BaZrO3 superlattices
    AIP Publishing ; 2002
    In:  Journal of Applied Physics Vol. 91, No. 4 ( 2002-02-15), p. 2284-2289
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 91, No. 4 ( 2002-02-15), p. 2284-2289
    Abstract: BaTiO 3  (BTO)/SrTiO3 (STO), and BaTiO3/BaZrO3 (BZO) artificial superlattices were fabricated by the molecular beam epitaxy process and their dielectric properties and refractive indices were measured. Superlattices formed on Nb-doped STO substrates showed large leakage currents in comparison with those on pure STO substrates. This indicated that Nb-doped substrates were not suitable for bottom electrodes in dielectric measurements. Dielectric properties were therefore measured for films on pure STO substrates using planar interdigital electrodes. Superlattice films were so thin (32 nm) that fine planer electrodes were necessary to reduce the penetration of electric flux into the substrate. Interdigital electrodes with the interdigital width of 5 μm were formed by electron beam lithography. Dielectric permittivity of superlattices was determined from admittance data using an electromagnetic field analysis. It was found that the dielectric permittivities of [(BTO)10/(STO)10]4 and [(BTO)10/(BZO)10] 4 were εr=720 000 and εr=330 000, respectively. A large Debye type dielectric dispersion was observed in the [(BTO)10/(BZO)10]4 superlattice. The refractive index of the superlattices was measured by spectroscopic ellipsometry. It was found that the refractive index of the superlattices changed with their structures and those of [(BTO)10/(STO)10] 4 and [(BTO)10/(BZO)10]4 superlattices were larger than other superlattices. This indicated that the superlattice structure affected not only on the ionic polarization but also the electronic structure or chemical bonding nature of the superlattices.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1433180
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2002
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 3
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    Electronic density of state in valence fluctuating kondo lattice systems studied by point-contact spectroscopy (Review article)
    AIP Publishing ; 2023
    In:  Low Temperature Physics Vol. 49, No. 7 ( 2023-07-01), p. 876-885
    Details
    In: Low Temperature Physics, AIP Publishing, Vol. 49, No. 7 ( 2023-07-01), p. 876-885
    Abstract: This article reviews our recent point-contact spectroscopy (PCS) investigation in valence fluctuating Kondo lattice systems, EuNi2P2 and Ge-substituted EuNi2(P0.8Ge0.2)2, and YbPd. A heavy fermion (HF) compound EuNi2P2 exhibits a significant valence fluctuation owing to the intermediate Eu valence of 2.5 + at low temperatures, leading to a strong hybridization between the conduction and f electrons (c–f hybridization). The electronic density of state measurements on EuNi2P2 by using PCS technique reveal that the HF behavior arises from the formation of the indirect hybridization gap with a double-peak structure near the Fermi level due to c–f hybridization. In EuNi2(P0.8Ge0.2)2, the valence fluctuation is suppressed by the Ge substitution, and the separation of the double-peak structure decreases. These suggest that the HF behavior is induced by the valence fluctuation. In YbPd, where two-dimensional (2D) layers of Yb3+ and Yb2.6+ are alternately aligned, a HF-like behavior with a large Sommerfeld coefficient appears at low temperatures in the specific heat. The PCS spectra represent a zero-bias dip structure with an asymmetric background, reproduced by the summation of two Fano curves with two different characteristic temperatures, meaning the formation of two Kondo resonance states for each Yb3+ and Yb2.6+ site. These suggest that a local coherence causes the large Sommerfeld coefficient in the 2D layers of Yb3+, which are screened by the conduction electrons provided by the valence fluctuating Yb2.6+ sites. The observed results indicate that PCS is a powerful technique for examining the variation of electronic DOS in valence fluctuating Kondo lattice systems.
    Type of Medium: Online Resource
    ISSN: 1063-777X , 1090-6517
    URL: Article
    DOI: 10.1063/10.0019701
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 1472502-2
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  • 4
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    Enhanced piezoelectric properties of barium titanate single crystals with different engineered-domain sizes
    AIP Publishing ; 2005
    In:  Journal of Applied Physics Vol. 98, No. 1 ( 2005-07-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 98, No. 1 ( 2005-07-01)
    Abstract: For tetragonal barium titanate (BaTiO3) single crystals, an electric field (E-field) applied along the [111]c direction can induce an engineered-domain configuration in these crystals. In this study, such engineered-domain configurations of different domain sizes were induced in BaTiO3 single crystals, and their piezoelectric properties were investigated as a function of domain size. Prior to this study, the dependences of the domain configuration on the temperature and E-field were investigated using a polarizing microscope in order to understand the optimum poling condition for fine- and coarse-domain configurations. We found that above the Curie temperature (TC) of 132.2 °C, when an E-field above 6.0kV∕cm was applied along the [111] c direction, an engineered domain with a fine-domain configuration appeared. Moreover, it was also found that this fine-domain configuration remained stable at room temperature without the E-field. On the other hand, the coarse-domain configuration was obtained upon poling at just below TC. Finally, the piezoelectric properties of 31 resonators with different domain sizes of 40–5.5μm were measured. As a result, it was found that the piezoelectric properties, such as d31 and k31, increased significantly with decreasing domain size.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1957130
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2005
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 5
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    Online Resource
    Artificial ferroelectricity in perovskite superlattices
    AIP Publishing ; 2004
    In:  Applied Physics Letters Vol. 85, No. 21 ( 2004-11-22), p. 5016-5018
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 85, No. 21 ( 2004-11-22), p. 5016-5018
    Abstract: Artificial superlattices of SrZrO3(SZO)∕SrTiO3(STO) were fabricated by molecular-beam epitaxy. Lattice parameters showed that the lattice distortion (c∕a ratio) attained a maximum value in the [(SZO)10∕(STO)10]4 superlattice. Dielectric relaxation was observed in the [(SZO)1∕(STO)1] 40 and [(SZO)10∕(STO)10]4 superlattices in the low frequency domain. Dielectric permittivity of the SZO∕STO superlattices was over 10 000 at 110MHz. The SZO∕STO superlattices showed clear Q–V hysteresis curves, which indicated that ferroelectricity was induced artificially in the superlattices in spite of the paraelectric nature of SZO and STO. The origin of the ferroelectricity was related to the anisotropic lattice distortion in the superlattice structure.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.1825057
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2004
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 6
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    Two-dimensional fluid dynamics in a sharply bent channel: Laminar flow, separation bubble, and vortex dynamics
    AIP Publishing ; 2016
    In:  Physics of Fluids Vol. 28, No. 10 ( 2016-10-01)
    Details
    In: Physics of Fluids, AIP Publishing, Vol. 28, No. 10 ( 2016-10-01)
    Abstract: Understanding the hydrodynamic properties of fluid flow in a curving pipe and channel is important for controlling the flow behavior in technologies and biomechanics. The nature of the resulting flow in a bent pipe is extremely complicated because of the presence of a cross-stream secondary flow. In an attempt to disentangle this complexity, we investigate the fluid dynamics in a bent channel via the direct numerical simulation of the Navier-Stokes equation in two spatial dimensions. We exploit the absence of secondary flow from our model and systematically investigate the flow structure along the channel as a function of both the bend angle and Reynolds number of the laminar-to-turbulent regime. We numerically suggest a scaling relation between the shape of the separation bubble and the flow conductance, and construct an integrated phase diagram.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    URL: Article
    DOI: 10.1063/1.4963864
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 7
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    Dielectric properties of BaTiO3/SrTiO3 superlattices measured with interdigital electrodes and electromagnetic field analysis
    AIP Publishing ; 2003
    In:  Journal of Applied Physics Vol. 94, No. 12 ( 2003-12-15), p. 7923-7925
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 94, No. 12 ( 2003-12-15), p. 7923-7925
    Abstract: Artificial BaTiO3(BTO)/SrTiO3(STO) superlattices on STO substrates were fabricated by the molecular beam epitaxy process. The capacitance and the complex admittance of superlattices with interdigital electrode structures were measured at 1–110 MHz. The dielectric properties of the superlattices were evaluated by the electromagnetic analysis. It was found that the dielectric permittivity changed with the structure of superlattices and the highest permittivity of 33 000 was obtained for [(BTO)10/(STO)10] 4 superlattice from 1 to 110 MHz.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1625780
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2003
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 8
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    Aspect ratio dependence of magnetoresistivity in polycrystalline bismuth microwire arrays
    AIP Publishing ; 2007
    In:  Journal of Applied Physics Vol. 101, No. 3 ( 2007-02-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 101, No. 3 ( 2007-02-01)
    Abstract: Magnetoresistivity measurements of polycrystalline bismuth microwire arrays having a range of different diameters and a bulk sample were performed under applied magnetic fields between 0 and 2T and temperatures from 50to300K. A thin film layer was deposited on the terminations of the microwire arrays in order to completely eliminate contact resistance. The measured resistivities were in very good agreement with those of polycrystalline bulk bismuth over the entire measured temperature range, even when the resistances had different values. The magnetoresistivities increased when a magnetic field was applied, and the rate of increase of the magnetoresistivities with applied magnetic field varied in samples having different aspect ratios. It was conjectured that this variation in the rate of increase is related to the aspect ratio. Suppression of magnetoresistivity in the microwire arrays was confirmed experimentally using bulk bismuth since the aspect ratio of the microwire arrays was much larger than that of the bulk sample. The geometrical contribution of the high aspect ratio on the magnetic effect in microwire and nanowire arrays makes it possible to enhance the thermoelectric performance of materials by suppressing the magnetoresistivity and increasing the magneto-Seebeck coefficient.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.2432876
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2007
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 9
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    Online Resource
    Growth condition dependence of morphology and electric properties of ZnO films on sapphire substrates prepared by molecular beam epitaxy
    AIP Publishing ; 2003
    In:  Journal of Applied Physics Vol. 93, No. 4 ( 2003-02-15), p. 1961-1965
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 93, No. 4 ( 2003-02-15), p. 1961-1965
    Abstract: Zinc oxide (ZnO) films were grown on sapphire (112̄0) substrates by molecular beam epitaxy under oxygen radical irradiation. The effect of the growth conditions, including the Zn/O ratio supplied to the film surface, on the electrical properties of ZnO films was studied in relation to the film morphology. We found that the growth rate strongly depended on the Zn flux from the Knudsen cell and the optimum condition for high growth rate was very narrow. The grain size in the lateral direction increased with increasing growth rate in the thickness direction. The increase in growth rate, especially in the lateral direction, resulted in the carrier mobility increasing up to 42 cm2 V−1 s−1. The carrier concentration N was sensitive to the substrate temperature, while the value of N was not sensitive to the source supplying ratio Zn/O. We discuss the decrease of the carrier concentration with increasing substrate temperature in regard to the formation of nonequilibrium defects.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1535256
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2003
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 10
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    X-ray absorption spectroscopy study of the instability of ferromagnetism in CeFe2: Effects of Co and Al substitutions
    AIP Publishing ; 2000
    In:  Journal of Applied Physics Vol. 87, No. 9 ( 2000-05-01), p. 6809-6811
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 87, No. 9 ( 2000-05-01), p. 6809-6811
    Abstract: We present in this work an x-ray absorption spectroscopy (XAS) investigation performed at the L3-edge of Ce in the intermetallic compounds Ce(Fe1−xCox)2 and Ce(Fe1−xAlx)2. The mixed-valence behavior of Ce is found to be preserved in both series upon Fe substitution. This result rules out the development of a localized 4f magnetic moment at Ce atoms driven by the Fe–Co and Fe–Al substitution at the origin of the anomalous magnetic behavior of this series.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.372849
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2000
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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