Low-Temperature Mechanochemical Synthesis of Zinc-Substituted Hydroxyapatite

Results of the investigation of the structure of zinc-substituted hydroxyapatite formed during low-temperature solid phase mechanochemical synthesis are presented. It is shown that a single-phase zinc-substituted hydroxyapatite with a degree of substitution of up to 0.4 mol zin. ions per 1 mol of hydroxyapatite is formed in a planetary ball mill AGO-2 after 30 min of mechanical impact on the mixture of initial reagents (CaHPO4, CaO, Zn(H2PO4)(2)center dot 2H(2)O). Two types of substitution reactions for zinc ions were studied: the substitution of calcium ions and hydroxide ions. The dynamics of lattice parameters of the synthesized samples showed that zinc ions most probably occupy the positions of calcium ions in the course of mechanochemical synthesis. After high-temperature treatment, the positions of zinc ions change: they are moved into the hydroxyl channel on the c axis, displacing OH groups and forming O-Zn-O chains elongated along the c axis. The limit of substitution, in this case, is reduced to 0.2 mol of zinc per 1 mol of hydroxyapatite. The synthesized samples may be used to obtain medical bioresorbable hardware and coatings with antibacterial properties.