AlPO4-18 synthesized from colloidal precursors and its use for the preparation of thin films

Nanosized AlPO4-18 is synthesized from clear precursor solutions; a complete transformation from amorphous to crystalline colloidal particles is observed after 60, 20 and 18 h at 100, 150, and 170 8C, respectively. The evaluation of the long-range ordering of nanocrystals as a function of crystallization time was followed by X-ray diffraction and dynamic light scattering. The time-dependent 27Al NMR measurements in the liquid phase before and after purifications with different crystallization times show that the tetrahedrally coordinated Al is formed at RT prior to hydrothermal treatment indicating the formation of crystalline phase. The mean hydrodynamic radius of the amorphous aluminophosphate entities and the crystalline AlPO4-18 particles does not change during the entire process of crystal growth. Further these AlPO4-18 nanocrystals were employed for the preparation of thin films on silicon wafers via spin coating of stable AlPO4-18/EtOH solutions, and additional crystal growth of the seeded layers at elevated temperature was carried out. The structural evolution of the thin films was studied with grazing incidence diffraction using synchrotron X-ray radiation. The orientation of growing crystals is governed by the preferred orientation of the seeded particles deposited by spin coating approach. # 2003 Elsevier B.V. All rights reserved.