To increase the biocompatibility of hydroxyapatite (HA), Ca10(PO4)6(OH)2,
the Sr substitution of Ca into the HA structure was effected to yield Ca10-xSrx(PO4)6(OH)2(Sr-HA).
For medical and dental applications, it is important
that Sr-HA is prepared as a thin film so that the Sr fully substitutes the Ca
sites in the HA structure and does not form segregated impurities consisting of
Sr compounds. If the segregated Sr forms different amounts of different
impurities, the dissolution of the Sr into the living body will not be
reproducible across different samples. To confirm the Sr substitution into the
Ca site in the HA structure, the systematic variation in the lattice constants
of the Sr-HA with Sr content was evaluated as the first step. The a- and c-axis lengths were found to exhibit a linear relationship with the Sr content for six samples with different Sr contents,
indicating that the prepared Sr-HA thin films likely possessed partial Sr
substitution into the Ca sites of the HA structure. This result is an important
first step in the accurate evaluation of the biological effects of Sr-HA thin
films.
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