Effect of composition of precipitated calcium-copper orthophosphates on their character

Abstract

A group of crystalline and amorphous calcium-copper phosphates was synthesized by the exchange reaction between sodium orthophosphate and calcium and copper(II) nitrates in solutions within a wide range of reagent ratios 0 ≤ Cu×100/(Cu + Ca) ≤ 100. Conclusions on the effect of the Cu×100/(Cu + Ca) ratio on the phase composition of the substances and on the state of chemical bonds therein were made on the basis of the results of X-ray phase analysis and IR Fourier and electronic spectroscopy.Calcium phosphate acid salts, like hydroxyapatite, tricalcium phosphate, and their amorphous analogs, are of interest as precursors of bioceramics with adjustable pore sizes [1-6]. Compounds of alkaline earth metals, silicates, and many other substances [7-11] may act as components efficiently influencing the porosity of ceramics obtained from phosphate precursors. Transition metal ions are of interest, as they allow fine control both of the microscopic structure and properties of ceramics. Copper is one of such examples, as its compounds impart strong antiseptic properties to materials [12][13][14][15]. We already described this element as a modifier of amorphous calcium phosphates, which substituted a small part of calcium cations in their composition [16]. In this communication we consider the nature of phosphates obtained from aqueous solutions at the simultaneous presence of calcium and copper in a wide range of 0 ≤ Cu×100/(Cu + Ca) ≤ 100 ratios.The synthesized compounds are pasty products with moisture content of 80-90 wt %. In air at room temperature phosphates erode rather fast, losing the main part of bound water and turning to solids with humidity of no more than 20% and an inorganic substance as a remainder. Therefore the pastes were dried in a thin layer in air at room temperature to a constant weight. The table gives an idea of the chemical composition of the resulting substances. Synthesized substances were studied by the methods of X-ray phase analysis, IR Fourier-and electronic spectroscopy.