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  • 1
    Electronic Resource
    Electronic Resource
    Temperature dependent Raman scattering in KTiOPO4 and KTiOAsO4 single crystals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3235-3240 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The longitudinal (LO) and transverse (TO) A1 vibrational modes have been measured between 30 and 1200 cm−1 as a function of temperature (30–1240 K) for both KTiOPO4 (KTP) and KTiOAsO4 (KTA). KTP and KTA exhibit an obviously different Raman spectra in the frequency region 400–650 cm−1 (with respect to KTA). This middle-frequency difference is attributed to the substitution ions in XO4 group (X=P or As) modifing the force constant of crystal. The relative intensities of the low-frequency bands increase dramatically with increasing temperature due to high mobility of K+ ion. There is no typical soft-mode like behavior in the measured frequency range. A higher symmetric structure taking place above Tc has been confirmed by the disappearance of the A1g(LO) stretching modes of TiO6 group. Comparison of each frequency belonging to the symmetry A1, A2, B1, and B2 measured along the [110] phonon direction shows complex difference. The vibrational frequencies of various symmetries were also obtained. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361270
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  • 2
    Electronic Resource
    Electronic Resource
    Ba(Mg1/3Ta2/3)O3 single crystal fiber grown by the laser heated pedestal growth technique (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4704-4708 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The preparation of Ba(Mg1/3Ta2/3)O3 (BMT) ceramics and the first successful growth of BMT single crystals by the laser heated pedestal growth technique (LHPG) is reported. The single crystal has a simple cubic perovskite structure in comparison to the ordered hexagonal structure normally found in ceramics of the same phase. The dielectric properties of single crystals are examined, the dielectric Q value increases with the increase in B-site ordering, while the dielectric constant κ is relatively independent of ordering. Our results also show that BMT is a candidate substrate for high Tc superconductor thin films as it has one of the highest Q values known for the oxide perovskite family, along with its matching thermal expansion coefficient α=9.0×10−6/ °C and twin-free cubic perovskite structure with a=4.0877 A(ring). BMT single crystals grown by the LHPG technique are probably the highest melting oxide compounds grown to date.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357003
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  • 3
    Electronic Resource
    Electronic Resource
    Epitaxial Sr2(AlTa)O6 films as buffer layers on MgO for YBa2Cu3O7−x thin film growth (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2138-2140 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sr2(AlTa)O6 thin films (2000–3000 A(ring)) have been deposited on MgO (001) substrates using pulsed laser deposition (PLD). X-ray-diffraction analysis shows that the Sr2(AlTa)O6 grows with the c axis highly oriented normal to the substrate plane and very good in-plane epitaxy. The subsequently deposited YBa2Cu3O7−x films using PLD on Sr2(AlTa)O6 buffered MgO substrates exhibit excellent epitaxial growth with a narrow rocking curve width and a small φ scan peak width. The critical temperature Tc0 of 90–92 K has been achieved reproducibly and the critical current density is over 2.7×106 A/cm2 at 77 K. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360197
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of microwave dielectric properties using the parallel-plate dielectric resonance technique (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3935-3936 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A modified field model of the parallel-plate open dielectric resonator is adopted to measure the dielectric constants and loss tangents of low loss materials. The measurement accuracy using this model is justified by comparing the results with those measured by other techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357409
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  • 5
    Electronic Resource
    Electronic Resource
    Micro-probe Raman spectroscopy for detection of inhomogeneities in YVO4 single crystals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2834-2838 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several near quasicongruent undoped YVO4 single crystals grown by the Czochralski (CZ) technique as well as near stoichiometric YVO4 single crystals grown by the top-seeded solution growth technique, were investigated by micro-probe Raman spectroscopy using unpolarized argon–ion laser light. The line broadening effects of the Raman active mode at 379 cm−1 indicate that all CZ grown crystals possess wider peak widths than near stoichiometric YVO4. In the latter case a value of 9.23 cm−1 was measured for full width at half-maximum. Although the annealing process in O2 can improve the oxygen stoichiometry in the originally slightly oxygen deficient CZ grown YVO4 crystals, certain remaining peak broadening effects demonstrate a Y–V related stoichiometry problem by both lower (external) and higher frequency (internal) modes. Radial inhomogeneous distributions were observed in CZ specimens by the shift of external Raman modes at 157 and 162 cm−1 frequencies. In addition, nonassigned low intensity extra Raman peaks appeared over 1000 cm−1 frequencies in all CZ grown samples. The above detected changes in Y–V–O stoichiometry demonstrate a complex phase system around the homogeneity region of quasicongruent YVO4 specimens and enable a more realistic and unified interpretation of the segregated defects and stoichiometry changes in CZ grown YVO4 single crystals than previously available. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361276
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  • 6
    Electronic Resource
    Electronic Resource
    Dielectric and pyroelectric properties of the morphotropic phase boundary lead barium niobate (PBN) single crystals at low temperature (10–300 K) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6405-6410 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature (10–300 K) dielectric and pyroelectric properties of morphotropic-phase-boundary lead-barium-niobate tungsten-bronze ferroelectric single crystals have been investigated. Strong "Debye-like'' dielectric dispersion, along a nonpolar direction (perpendicular to the polarization direction), has been observed and characterized by dielectric spectrum techniques. A direct charge measurement method has been used to study the low-temperature pyroelectric properties in polar and nonpolar directions. A "frozen-in'' polarization component in a nonpolar direction is also reported. The low-temperature relaxation effects are explained by the internal reorientation polarization perturbation and a thermally agitated local dipole fluctuation model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345164
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  • 7
    Electronic Resource
    Electronic Resource
    Pyroelectric, piezoelectric, and dielectric properties of β-BaB2O4 single crystal (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 6186-6188 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dielectric and pyroelectric properties of single-crystal β-barium metaborate (β-BaB2O4) are measured in the temperature range from 50 °C down to −190 °C. Thermal expansion and piezoelectric properties are measured at room temperature. Piezoelectric and electromechanical coupling coefficients in β-BaB2O4 are low where as pyroelectric figure of merit p/K is quite attractive for some device applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343556
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  • 8
    Electronic Resource
    Electronic Resource
    Negative thermal expansion behavior in single crystal and ceramic of Nb2O5-based compositions (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5051-5054 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal expansion coefficients of a single crystal and ceramic of Nb2O5 are measured in the temperature range of −200–500 °C by the dilatometer technique. Both single crystals and ceramics of Nb2O5 and Nb2O5(1−x):xTiO2 show negative thermal expansion in this temperature range. Some contribution to the result could be due to the presence of the Magneli phases. The main phase transition temperature, which also matches with the dielectric anomaly, occurs at (approximate)150 °C. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1464232
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  • 9
    Electronic Resource
    Electronic Resource
    Dielectric behavior of Ba(Ti1−xZrx)O3 single crystals (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 410-415 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we report the successful growth of Ba(Ti1−xZrx)O3 (x=0.05–0.2) single-crystal fibers by the laser-heated pedestal growth technique. A single-phase perovskite structure of the materials has been identified by the x-ray diffraction technique. The phase diagram for Ba(Ti1−xZrx)O3 single crystals is established for x≤0.2. Dielectric properties as function of temperature and frequency and room-temperature hysteresis loops are measured. The remnant polarization (Pr) and coercive fields (Ec) are obtained and compared for both single crystals and ceramics. The small dielectric relaxation has been observed for the lower-temperature phase transition (around 40 °C at 1 kHz) of the sample with x=0.08. The relaxation times follow the Arrhenius law with τ0=0.4×10−13 s and Erelax=0.53 eV. A common feature of the low-temperature relaxation mode in the sample is also observed, which follows the Arrhenius law with the τ0=0.8×10−10 s and Erelax=0.46 eV. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373674
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  • 10
    Electronic Resource
    Electronic Resource
    Dielectric relaxation processes in Cd2Nb2O7 compound (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7452-7456 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article reports a study on the dielectric relaxation processes of Cd2Nb2O7 compound. Three dielectric relaxation modes I, II, and III were reexamined. By using the Cole–Cole equation fitting of the frequency dependence of dielectric constant and loss, we obtained more precise relaxation time data, compared to the data reported in the literature. The results indicate that the relaxation time for mode I follows the Arrhenius law with one slope rather than two slopes as reported in the literature in the frequency range of 102–105 Hz. However, the parameters obtained from the Arrhenius law fit are not physically reasonable. More physically reasonable parameters can be obtained by fitting the relaxation time to the empirical Vogel [Z. Phys. 22, 645 (1921)]–Fulcher [J. Am. Ceram. Soc. 8, 339 (1925)] relation with essentially the same fitting quality. A comparison of Cd2Nb2O7 with well known triglycine sulphate (TGS) is made. The similarity between the dielectric response of Cd2Nb2O7 and TGS is emphasized. The physical mechanism of the relaxation modes is briefly discussed. With increasing dc bias, the three relaxation modes were suppressed and eventually eliminated. This indicates that the dielectric responses of Cd2Nb2O7 at zero dc bias are the sum effect of several dielectric modes with relaxation polarization superimposed on the ferroelectric–paraelectric phase transition. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373009
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