SYNTHESES AND THERMAL BEHAVIORS OF SOME CATION-MIXED CYCLO-PHOSPHATES

Abstract

Cation-mixed cyclo- tri and hexaphosphates, M^IIM^IP₃O₉·nH₂O and M^II₂M^I₂P₆O₁₈·nH₂O, were synthesized by Boulle's process, where M^I was alkaline earth metal (Mg, Ca, Sr, Ba) and MI was alkali metal (Li, Na, K). Some of these cyclo-hexaphosphates could not be obtained because of their insolubility to water or coprecipitation with AgCl. Resulting salts were characterized and their thermal behaviors were investigated by using DTA-TG, XRD, HPLC-FIA and ICP-AES. All of these salts have some extents of water. On heating, accompanied by dehydration, they hydrolyzed into ortho-, pyro- and triphosphates at 50-200°C. At 200-400°C, these phosphates gradually condensed to insoluble phosphates. Then these phosphates crystallized to 5 kinds of poly- or cyclo-phosphates at 400-600°C. Therefore their thermal behaviors could be classified into 5 different types.