Effects of temperature on the formation of hydroxyapatite


The formation of hydroxyapatite by an acid-base reaction between solid calcium phosphates at temperatures from 5 to 60 °C was examined. The basic reactant used is Ca4(PO4)2O, while the acidic reactants include CaHPO4, CaHPO4 · H2O, and Ca(H2PO4)2 · H2O. Rates of heat evolution during reaction were determined by isothermal calorimetry. The variations in the proportions of reactants and hydroxyapatite and the formation of intermediate products were assessed by x-ray diffraction. Development of microstructure was observed. Generally, hydroxyapatite formation occurs by rapid initial reaction followed by a period during which reaction occurs slowly. Apparent activation energies calculated for the reaction when CaHPO4 is the acidic reactant show differing values depending on its surface area. When the acidic reactant is Ca(H2PO4)2 · H2O, intermediate products are formed. At low temperatures the intermediate is CaHPO4 · 2H2O, while at higher temperatures it is CaHPO4. Above 38 °C, the rate during the period of slow reaction decreases with increasing temperature. This appears to be related to the retrograde solubilities of the reactants, CaHPO4 · 2H2O and CaHPO4, and of HAp.

This is a preview of subscription content, access via your institution.


  1. 1

    W. E. Brown and L.C. Chow, Cements Research Progress-1986, edited by P. W. Brown (American Ceramic Socielv, Westerville, OH, 1987), pp. 351–379.

    Google Scholar 

  2. 2

    M. Fulmer and P. W. Brown, in Male-rials Synthesis Utilizing Biological Processes, edited by P. C. Rieke. P. D. Calvert, and M. Alper (Mater. Res. Soc. Symp. Proc. 174, Pittsburgh, PA, 1990), p. 39.

    Google Scholar 

  3. 3

    M. Fulmer and P. W. Brown, J. Am. Ceram. Soc. 74. 934–940 (1991).

    Article  Google Scholar 

  4. 4

    P.W. Brown. N. Hocker, and S. Hovlc, J. Am. Ccram. Soc. 74, 1855–1861 (1991).

    Article  Google Scholar 

  5. 5

    M.T. Fulmer, R.I. Martin, and P.W. Brown, J. Mater. Sci. Materials in Medicine (in press).

  6. 6

    P.W. Brown, J. Am. Ceram. Soc. 75, 17–22 (1992).

    CAS  Article  Google Scholar 

  7. 7

    H.F. W. Taylor, Cement Chemistry (Academic Press. New York, 1990).

    Google Scholar 

  8. 8

    S-S. Feng and T.J. Rockett, J. Am. Ceram. Soc. 62, 619 620 (1979).

    CAS  Article  Google Scholar 

  9. 9

    T. M. Gregory. K. G. Moreno, J. M. Petal, and W. E. Brown, J. Res. Natl. Bur. Stand. 78A, 667–674 (1974).

    CAS  Article  Google Scholar 

  10. 10

    J. VanWazer, Phosphorous and Its Compounds, Vol. I: Chemistry (1958).

  11. 11

    H. McDowell, T. M. Gregory, and W. E. Brown, J. Res. Natl. Bur. Stand. 81A, 273–281 (1977).

    CAS  Article  Google Scholar 

  12. 12

    R. Martin and P.W. Brown, unpublished work.

  13. 13

    B. B. Tomazic, M.S. Tung, T. M. Gregory, and WE. Brown, Scan. Micro. 3 (1), 119–127 (1989).

    CAS  Google Scholar 

  14. 14

    W.E. Brown, J.R. Lehr, J.T. Smith, and A.W. Frazier, Nature 196, 1050–1055 (1962).

    CAS  Article  Google Scholar 

  15. 15

    R.Z. LeGeros, G. Daculsi, J. Orly, T. Abergas, and W. Torres Scan. Micro. 3 (1), 129–138 (1989).

    Google Scholar 

Download references

Author information



Rights and permissions

Reprints and Permissions

About this article

Cite this article

Fulmer, M.T., Brown, P.W. Effects of temperature on the formation of hydroxyapatite. Journal of Materials Research 8, 1687–1696 (1993). https://doi.org/10.1557/JMR.1993.1687

Download citation