Ceramic Materials with a Prescribed Phase Composition Based on Hydroxyapatite Powder Processed in Dihydrogen Phosphate Solutions of Ammonium, Sodium, and Potassium

Hydroxyapatite (HA) Ca 10 (PO 4 ) 6 (OH) 2 powders kept for 1 h with stirring in 0.25 M aqueous solutions of dihydrogen phosphates of ammonium NH 4 H 2 PO 4 , sodium NaH 2 PO 4 , and potassium KH 2 PO 4 were used to obtain ceramics. According to XRD data, there were no changes in the phase compositions of powders after such treatment. After firing at 900 – 1100°C the phase composition of ceramics based on HA Ca 10 (PO 4 ) 6 (OH) 2 powder treated with an aqueous solution of NH 4 H 2 PO 4 included β-tricalcium phosphate β-Ca 3 (PO 4 ) 2 and HA Ca 10 (PO 4 ) 6 (OH) 2 ; the phase composition of ceramics based on HA powder Ca 10 (PO 4 ) 6 (OH) 2 treated with an aqueous solution of NaH 2 PO 4 included sodium-substituted tricalcium phosphate Ca 10 Na(PO 4 ) 7 and HA Ca 10 (PO 4 ) 6 (OH) 2 ; the phase composition of ceramics based on HA powder Ca 10 (PO 4 ) 6 (OH) 2 treated with an aqueous solution of KH 2 PO 4 included potassium-substituted tricalcium phosphate Ca 10 K(PO 4 ) 7 and HA Ca 10 (PO 4 ) 6 (OH) 2 . The formation of biphasic ceramics occurred because of reduction in the Ca/P molar ratio of HA Ca 10 (PO 4 ) 6 (OH) 2 powder after treatment in aqueous solutions of dihydrogen phosphates of ammonium NH 4 H 2 PO 4 , sodium NaH 2 PO 4 , and potassium KH 2 PO 4 . Adsorption of cations and anions from solutions on the surface of HA particles, slight dissolution of HA in aqueous solutions of dihydrogen phosphates with acidic pH, as well as ion exchange of cations and anions in the HA structure for cations and anions from solutions were possible processes effecting change in the ratio of cations and anions in HA powder. The resulting ceramic composites contain biocompatible phases and can be recommended for creating bone implants.