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  • 2000-2004  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Proton transport polarization and depolarization of hydroxyapatite ceramics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5386-5392 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarization of sintered hydroxyapatite (HAp) ceramics by application of an external dc field at higher temperature was analyzed by thermally stimulated depolarization current (TSDC) measurements. The mechanisms for the polarization and depolarization of HAp were discussed in relation to the instability of the protons in the hydroxide groups. The TSDC spectra consisted of broad peaks, while the ferroelectric substances such as the BaTiO3 ceramics exhibited a sharp peak. Although the maximum current density of 7.87 nA cm−2 for the HAp polarized at 400 °C under 1.0 kV cm−1 was approximately 1/12 lower than that of BaTiO3, the polarization charge of 14.9 μC cm−2 was almost twice as large as that of BaTiO3. Considering the activation energy of 0.72–0.89 eV for the depolarization, it was revealed that the polarization of HAp was ascribed to the migration of protons in the columnar OH− channels with a micrometer-order distance. It was also found that the polarization charge was large and long enough to enhance the biological reactivity of HAp ceramics for biomedical implants. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357783
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of aluminum substitution in La3Ga5SiO14 crystals on their structure and piezoelectricity (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4201-4203 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report La3Ga5−xAlxSiO14 (0≤x≤1) crystals, with a Ca3Ga2Ge4O14-type structure, suitable for piezoelectric application. A single-crystal x-ray structure analysis reveals that Al atoms are distributed in all cation sites except for the decahedral one occupied by La, by rather favoring the smallest tetrahedral one. The piezoelectric modulus |d11| increased ∼1.3% and d14 decreased ∼7.7% with the increasing Al content, x, up to 1.0. We discuss the possible correlation between the atomic displacement and the observed compositional dependence of the piezoelectric modulus |d11| by referring to other isomorphs. The optimal solid-solution compositions and the use of Al substitution for obtaining the maximum electromechanical coupling factors (k12, k25, and k26) are advanced. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1426274
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  • 3
    Electronic Resource
    Electronic Resource
    Formation Mechanism and Synthesis of Apatite-Type Structure Ba2+xLa8−x(SiO4)6O2−δ (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), 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 formation process of Ba2La8(SiO4)6O2 was clarified using thermogravimetry–differential thermal analysis (TG-DTA) and a high-temperature powder X-ray diffraction (HT-XRD) method. Phase changes identified from the HT-XRD data surprisingly corresponded to the weight loss and/or endothermic peaks observed in the TG-DTA curves. Raw material with the composition Ba2La8(SiO4)6O2 was completely reacted at 1400°C and produced only an apatite-type compound without a secondary phase. Moreover, the synthesis of Ba2+xLa8−x(SiO4)6O2−δ crystals with x= 0–2 was attempted using a solid-state reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01654.x
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