Some magnesium phosphates were prepared by adding a Mg (NO3) 2 solution into mixed solutions of KOH and H3PO4 at temperatures of 25-95°C, and investigated with respect to their formation processes and chemical compositions.
The formation regions of the resulting magnesium phosphates were mainly affected by synthetic temperature and pH. Namely, MgHPO4·3H2O (DMP3) was formed in an acidic pH region at 25-29°C, while in an alkaline pH region, KMgPO4·6H2O (KMP6) and KMgPO4·H2 O (KMP1) were formed at 25-60°C and 70-95°C, respectively. Further, a double salt of Mg3 (PO4) 2 hydrate and potassium phosphate was formed under a limited conditions of temperature (50-95°C) and pH (near 7).
KMP6 changed to an amorphous phase at 100°C by dehydration of 6 moles of water corresponding to the lattice water, and crystallized to KMgPO4 (KMP) at 380°C. On the other hand, KMP1 changed to an amorphous phase by dehydrating the lattice water at 200°C, and crystallized to KMP at 470°C.
By suspending KMP6 in water, KMP6 varied to Mg3 (PO4) 2·22H2O (TMP22) at 40°C, and to Mg3 (PO4) 2·8H2O (TMP8) at temperatures between 60°C and 80°C.
