LARGE ALPO4-5 CRYSTALS BY MICROWAVE-HEATING

Microwave heating is applied to the synthesis of AIPO(4)-5. After 60 s of heating, large AIPO(4)-5 crystals are obtained. XRD, polarization microscopy, and adsorption measurements prove the regularity of the AFI framework. In an optimized microwave synthesis prismatic AIPO(4)-5 crystals up to 130 mu m long and 40 mu m thick could by synthesized. In a two-step synthesis, however, slightly smaller, but very uniform AIPO(4)-5 crystals with a narrow crystal size distribution without any amorphous or crystalline byproducts could be obtained. Several possible mechanisms for the fast crystallization within 60 s by microwave radiation are discussed: an increased dissolution of the gel by lonely water molecules, the almost T-gradient-free and, therefore, convection-free in situ heating, and the existence of organic-inorganic arrays as local microassemblies which could transform directly into the AR framework.