Electrical conductivity of polycrystalline hydroxyapatite and its application to electret formation

Hydroxyapatite (HAp), a type of calcium phosphate found in bones and teeth, exhibits proton conductivity. In this study, its conductivity is investigated by measuring the complex permittivity of polycrystalline hydroxyapatite samples obtained via a sintering process. The dielectric dispersions measu...

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Bibliographic Details
Published in:Solid state ionics 2018-02, Vol.315, p.19-25
Main Authors: Horiuchi, Naohiro, Madokoro, Kazuki, Nozaki, Kosuke, Nakamura, Miho, Katayama, Keiichi, Nagai, Akiko, Yamashita, Kimihiro
Format: Article
Language:English
Subjects:
Biomedical materials
Bones
Calcium phosphates
Complex permittivity
Conductivity
Deoxidizing
Electrets
Electrical resistivity
Grain boundaries
High impedance
Hydroxyapatite
Polarization
Polycrystals
Protons
Sintering
Studies
Surgical implants
Thermally stimulated depolarization current
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Summary:Hydroxyapatite (HAp), a type of calcium phosphate found in bones and teeth, exhibits proton conductivity. In this study, its conductivity is investigated by measuring the complex permittivity of polycrystalline hydroxyapatite samples obtained via a sintering process. The dielectric dispersions measured from samples with different grain sizes are successfully explained using the Maxwell-Wagner interfacial polarization model. The results show that polycrystalline hydroxyapatite consists of both a high impedance grain boundary and a proton-conductive grain that has a conductivity of about 1.0×10−7Scm−1 at 573K. The interfacial polarization is confirmed using thermally stimulated depolarization current measurements. Additionally, electrets are prepared with the polycrystalline HAp via a poling process, and it is demonstrated that the electret formation is caused by the interfacial polarization. •Hydroxyapatite conductivity is studied via complex permittivity measurements.•The hydroxyapatite consists of conductive grains and insulative grain boundaries.•Interfacial polarization is confirmed via depolarization current measurements.•The interfacial polarization makes the hydroxyapatite an electret.
ISSN:0167-2738
1872-7689
DOI:10.1016/j.ssi.2017.11.029