Wet-chemical formation of aluminophosphates

From refractory bonding, aluminophosphates are known to be hard and stable compounds. Porous AlPO4 is widely studied, but little is known about compounds with a P/Al molar ratio higher than 1. Here we report on the formation of several aluminophosphates from acidic precursor solutions. We describe the reaction leading to the formation of Al(PO3)(3) in more detail. Addition of HCl to the precursor solution leads to a monoclinic rather than the cubic phase of Al(PO3)(3). Optimum formation temperature is 300 - 400degreesC, as at higher temperatures H3PO4 escapes before the reaction has been completed.