Effect of nonstoichiometry and amount of additives on the structure of HAp-TiO$_y$ mixtures produced by high-energy fragmentation

The nanoparticle sizes in hydroxyapatite (HAp), titanium monoxide (TiO$_y$) and HAp-TiO$_y$ mixtures ($y = 0.92$; $1.23$) have been studied by XRD and HRTEM techniques as a function of milling time. It was established that the high-energy milling does not lead to a considerable decrease in the particle size and to a variation in the HAp crystal lattice parameters, but it promotes $4$-fold reduction of microstrains. It was shown that the dependence of the average size of crystal and structural parameters on the milling time for the HAp-TiO$_y$ mixtures is similar to that of initial HAp. The coherent scattering region of HAp does not depend on stoichiometry and TiO$_y$ content in the mixture andis $\sim15 \pm 5$ nm after milling for $480$ min.