In this communication, we demonstrated the growth of aluminum phosphate ammonium taranakite (NH4-AlPO4) crystals from regular hexagonal form into the disk-like form could be controlled by ammonium citrate (AMC) as the effective crystal growth modifier at 90 degrees C. Prepared crystals were characterized by field emission scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of AMC's concentration on the crystal form and morphology of NH4-AlPO4 were studied. The results showed that the AMC's concentration is an important parameter to control the size and morphology of NH4-AlPO4 crystal. The formation mechanism of the special morphology of NH4-AlPO4 crystals was also analyzed. (C) 2009 Elsevier B.V. All rights reserved.