Crystallization of nanosized Aurivillius phase Bi2W2O9 from amorphous precursor

Nanoparticles of bismuth layered Aurivillius phase, Bi₂W₂O₉, have been synthesized by annealing of precursor prepared by high energy milling in ball mill. The obtained powders have been investigated using the XRD, TEM, SEM, diffuse reflectivity, Raman and infrared spectroscopy. The results show that mechanochemical activation allows obtaining Bi₂W₂O₉ at much lower temperatures than those required in a conventional solid state reaction or synthesis through a complex organic precursor. As a result, material with smaller grain size can be obtained. Therefore this synthesis method is the best route to enhance photocatalytic activity of Bi₂W₂O₉. Our results also show that milling time has great impact on the crystallization mechanism. Bi₂W₂O₉ crystallizes easily already at 600 °C from precursor milled by 8 h. However, prolong milling time results in stabilization of an unknown phase or phases, which crystallize below 700 °C, and transform into the well-known Bi₂W₂O₉ phase after annealing at 750 °C.