Funct. Mater. 2016; 23 (3): 394-397.

Phase composition, coherence lengths and micro-strain level in hydroxyapatite films with controlled deviation from stoichiometry (Ca/P = 1.67) were measured by methods of X-ray diffraction and X-ray fluorescent analysis. It was established that at Ca/P = 1.6±0.03, hydroxyapatite layers with thickness 2m on the niobium substrates were practically single-phase but differed by the coherence lengths and micro-strain levels for different crystallographic directions: the coherence length along [001] was commensurable with the film thickness and much exceeded the values for [101] and [111] directions. The micro-strain level ε for [001] direction reached (1.3÷1.7)·10^-3 being by an order higher than for [101] and [111] directions. That testifies constrained growth conditions along [001] with the high homogeneity of the lattice period of the hydroxyapatite film.