Journal of Materials Science

, Volume 41, Issue 2, pp 525–530 | Cite as

Transmission electron microscopic observation of a metastable phase on the thermal decomposition process of Ca-deficient hydroxyapatite

  • Masato TamaiEmail author
  • Toshiyuki Isshiki
  • Koji Nishio
  • Mitsuhiro Nakamura
  • Atsushi Nakahira
  • Hisamitsu Endoh


Calcium-deficient hydroxyapatite (Ca-def HAp) decomposes to stoichiometric hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) at high temperature. In a previous study, we reported that a metastable phase with a high Ca/P molar ratio appeared in the temperature range from 700 to 800°C. In the present study, the formation process of a metastable phase and the crystallographic relationship between the Ca-rich metastable phase and HAp matrix were investigated by high-resolution transmission electron microscopy (HRTEM). Ca-def HAp was annealed at 600–850°C for 2 or 6 h in air. TEM observations were performed before and after annealing Ca-def HAp. Based on analysis of image of Ca-def HAp before annealing, several HAp crystals with different aspect ratios agglomerated. The metastable phases grew thicker by long-term annealing. HRTEM image suggested that the Ca-rich metastable phase was formed by migration to the interface and continuous accumulation of calcium ions from HAp crystals with a small aspect ratio. From HRTEM images and results of the analysis of selected area electron diffraction patterns along the [010], [110] and [001] zone axes, lattice constants of the metastable phases were determined to be a = 2.86 nm, b = 0.94 nm, and c = 0.69 nm with orthorhombic crystals system.


Hydroxyapatite Select Area Electron Diffraction Electron Diffraction Pattern HRTEM Image Transmission Electron Microscopic Observation 


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Copyright information

© Springer Science + Business Media, Inc. 2006

Authors and Affiliations

  • Masato Tamai
    • 1
    Email author
  • Toshiyuki Isshiki
    • 2
  • Koji Nishio
    • 2
  • Mitsuhiro Nakamura
    • 2
  • Atsushi Nakahira
    • 1
  • Hisamitsu Endoh
    • 2
  1. 1.Department of Chemistry and Materials TechnologyKyoto Institute of TechnologyKyotoJapan
  2. 2.Department of Electronics and Information ScienceKyoto Institute of TechnologyKyotoJapan

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