ISSN 1027-4510, Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2014, Vol. 8, No. 6, pp. 1128–1136. © Pleiades Publishing, Ltd., 2014. Original Russian Text © E.P. Domashevskaya, A.A. Al-Zubadi, D.L. Goloshchapov, N.A. Rumyantseva, P.V. Seredin, 2014, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2014, No. 11, pp. 42–50. 1128 INTRODUCTION Calcium hydroxyapatite (HAP) Ca 10 (PO 4 ) 6 (OH) 2 is an important material used in the reconstruction of human bone tissue. Synthetic HAP and materials on its basis are used in medicine in the form of ceramics and composites which substitute lost bone and also as coatings of implants enabling a bond between hydroxyapatite and the bone tissue [1–5]. Materials on the basis of HAP with different properties are required in orthopedics depending on the type of bone and the individual features of a person. The characteristics of hydroxyapatite can be altered upon the introduction of different substituents into the cation and anion sublattices in the HAP struc- ture. Calcium-deficient hydroxyapatite is the best mate- rial for these aims due to its high chemical activity. This material is most often used during the reconstruction and regeneration of natural human bone tissue. It is known that metal ions (Na, Mg, Zn, Cu, Fe, Sr) in the composition of bone-tissue hydroxyapatite play an important role in the process of osteogenesis and affect the properties of biogenic HAP [6, 7]. The purposeful introduction of metal ions into the lattice of synthetic hydroxyapatite samples can lead not only to the improvement of biocompatibility but also to a change in the structurally conditioned properties of these materials [7]. Among other microelements, zinc and copper actively participate in the process of osteo- genesis. Zinc is present both in human tooth enamel and bone tissue and increases the activity of osteo- blasts during the course of bone resorption, plays an important role in the human immune system [7, 8]. Copper ions (Cu +2 ) the same as silver ions (Ag + ) have an antibacterial effect and in low concentrations facil- itate an antiseptic effect on the damaged region of the bone tissue [9]. These metals are the best for improve- ment of the bioactive properties of HAP. In [6, 7, 10] samples of metal-substituted HAP were obtained using chemical deposition from a solution, and the characteristics of the copper- and zinc-substituted HAP and their comparison with other calcium phos- phates were presented. However, the structure, phase composition and temperature stability of similar modified HAP samples determining their physico- chemical properties as a function of the impurity concentration were studied in [6, 7, 10] not compre- hensively enough. This work is aimed at determining the influence of metal ions Zn +2 and Cu +2 on the phase composition and structure of calcium-deficient hydroxyapatite. MATERIALS AND METHODS OF SAMPLE PREPARATION Impurity-free calcium-deficient hydroxyapatite (CDHAP) was obtained by chemical deposition from a solution according to the technique described in [9, 11, 12]. A given amount of 0.3 M solution (NH 4 ) 2 HPO 4 was gradually introduced into a solution of 0.5M Ca(NO 3 ) 2 ⋅ 4H 2 O. Then a 25% solution of ammonia NH 4 (OH) was added to the formed suspen- Structure and Composition of Metal-Substituted Calcium-Deficient Hydroxyapatite E. P. Domashevskaya, A. A. Al-Zubadi, D. L. Goloshchapov, N. A. Rumyantseva, and P. V. Seredin Voronezh State University, Voronezh, 394006 Russia e-mail: ftt@phys.vsu.ru Received February 15, 2014 Abstract—Calcium-deficient hydroxyapatite (CDHAP) and metal-substituted hydroxyapatite (Me-HAP) are prepared by chemical deposition from solutions of relevant compositions. Powderlike samples are stud- ied by X-ray diffraction (XRD), electron probe microanalysis (EPMA), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The XRD and EPMA data show that under certain conditions cal- cium-deficient hydroxyapatite CDHAP could be produced with a calcium to phosphorus ratio of Ca/P = 1.43 and with an average nanocrystal size of ~50 nm. The calcium deficiency in the hexagonal structure of Me-HAP is also retained upon the partial replacement of calcium with Zn and Cu atoms with smaller radii. The lattice parameters and the average sizes of the nanocrystals of Me-HAP are lower as compared with undoped CDHAP. DOI: 10.1134/S1027451014060032