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Table I.
Characteristics of calcium phosphate phases. Ksp, solubility product constant.
| Solid phase | Chemical reaction in aqueous solutions | Ca/P | −Log Ksp | Formation conditions pH/temperature (°C) | References |
|---|---|---|---|---|---|
| Brushite or DCPD | Ca2+ + HPO42− + 2H2O = CaHPO4·2H2O (aq) | 1 | 6.68 | 4–6/25; 4–6/37; 4/60 | [11, 14, 17] |
| OCP | 8Ca2+ + 2HPO42− + 4PO43− + 5H2O = Ca8(HPO4)2(PO4)4·5H2O (aq) | 1.33 | 46.9 | 6.5/37; 5/60; 4/80 | [14] |
| HAP | 10Ca2+ + 6PO43− + 2OH− = Ca10(PO4)6(OH)2 (aq) | 1.67 | 57.74 | 7–9/60; 6–9/80 | [14, 18] |
| CDA | (10−x)Ca2+ + xHPO42− + (6−x)PO43− + (2−x)OH− = (10−x/6)Ca10−x(HPO4)x(PO4)6−x(OH)2−x (aq) | (0 < x ≤ 2) | – | 7.5–9/37 | [14] |