Preparation, characterization, and stability of calcium zinc hydrophosphate

Calcium zinc hydrophosphate phases with different Zn/(Zn + Ca) molar ratios (xZn, from 0 to 1) were synthesized using co-precipitation method at pH 10, 25 °C. X-ray diffraction, FT-IR spectroscopy and field emission scanning electron microscopy (FE-SEM) were used to characterize the synthesized products. Thermal behavior of the products was examined by thermal analytical instruments (TG–DSC–MS), while the chemical stability of the products was tested by toxicity characteristic leaching procedure (TCLP).The results showed that the phase constituents of formed calcium zinc hydrophosphate phases were related to the molar contents of Zn2+. With the increase of xZn, it formed calcium-deficient hydorxyapatite (CaHap), calcium zinc hydorxyapatite (CaZnHap), CaZn2(PO4)2·2H2O, and Zn3(PO4)2·4H2O, respectively. All the calcium zinc hydrophosphates were thermally stable up to 600 °C, and less Zn2+ leached in a wide pH range of 2–11, which indicated that calcium zinc hydrophosphate could effectively hold Zn2+ in their crystal phases with stabilization ratios of over 99.99%.