Physico-chemical characterization of calcium-apatite prepared with a calcium/phosphate ratio around the stoichiometry

Calcium phosphate materials synthesized from apatite with atomic Ca/P ratios ranging from 1.50 to 1.67 (Ca 10- x (HPO 4 ) x (PO4) 6- x (OH) 2- x (0 ≤ x ≤ 1)) have very interesting applications in bone regeneration and in the environment field for the removal of toxic species. The physicochemical characteristics of synthetic calcium apatite change when the Ca/P ratio varies. In this study, two batches of apatite powder were prepared by precipitation in an aqueous medium at 25 °C with Ca/P molar ratios that were close to those of tricalcium phosphate (1.48, 1.50, and 1.52) and close to those of hydroxyapatite (1.65, 1.67, and 1.72). For dried and ceramized powders, the chemical composition, morphology, surface area, compacity, durability, and crystalline phases of prepared powders were studied. The result shows that the dried powders composed of nanocrystals are poorly crystallized. The sample with the lowest Ca/P atomic ratio (1.48) shows the lowest specific surface area (75 ± 5 m 2 /g) with good compaction ability and acceptable mechanical properties. While stoichiometric HAP (Ca/P = 1.67) has a large specific area (110 ± 5 m 2 /g), however, it has poor compaction properties. Calcined apatite (Ca/P = 1.65) at 900 °C composed of HAP with traces of tricalcium phosphate (Ca 3 (PO 4 ) 2 : βTCP) shows a higher compressive strength (78 ± 10 MPa). βTCP ceramic with Ca/P = 1.48 has the lowest optical gap (OG = 4.6 ± 0.4 eV). The result of this study shows how little changes in the Ca/P ratio had an impact on the granular properties of dried and calcined calcium phosphate materials. Apatite produced with slightly sub-stoichiometric calcium has the potential for promising future uses in the biological, catalytic, and environmental domains.