In situ TEM observation of crystallization of amorphous ordered mesoporous Nb-Ta and Mg-Ta mixed oxides

The crystallization of ordered mesoporous Nb-Ta and Mg-Ta mixed oxides in a vacuum is observed in situ by transmission electron microscopy (TEM). Both metal oxides become polycrystalline upon heating, yet retain the pore size and ordered structure of the amorphous precursors. The crystalline structure and meso-structure of the materials obtained by crystallization in a vacuum differ from those produced by crystallization in air, suggesting the possible role of atmospheric oxygen in the crystallization process.