The soft chemistry of molybdenum and tungsten oxides: A review

Through various examples the potential of soft chemistry is illustrated. Using the structural filiation between a mother and a daughter phase, supermetastable and metastable oxides have been obtained. Studies have shown that these oxides are good materials for comparative studies of intercalation chemistry. These studies have been performed in order to compare the intercalation effects of hydrogen and lithium in the metastable and supermetastable oxides in accordance with their structures (1D or 3D tunnels) and with the Mo/W ratio. It can be concluded that the more isotrope the structures are (3D tunnels of the pyrochlore structure for example), the less distorted they are. Lithium leads to an amorphization at high intercalation rates, which is not observed in the case of hydrogen. Molybdenum compounds allow high intercalation rates but deintercalation is difficult to perform; it is the reason why it is difficult to consider their use as electrochromic displays.