Low temperature syntheses of highly-ordered framework materials: The aluminium phosphate ammonium taranakite

The formation of a highly crystalline ammonium analogue of the aluminium phosphate mineral taranakite at ambient temperature and above is described. The high crystallinity and ordering of the products obtained when ammonium is used as a templating agent suggests that it is intimately involved in the structure. At long crystallization times and at higher temperatures, transformation to the framework structure of AlPO4-15 occurs. Results from powder x-ray diffraction, solid state NMR, electron microscopy, thermal and element analyses are presented and discussed. They demonstrate the high degree of crystallinity and ordering of the taranakite samples synthesized by this method. These results - in particular the very mild synthesis conditions - suggest the possibility that there may be sequestering of ammonium phosphate fertilizers in form of NH4-taranakite from their interaction with clay materials in soils.