Generally, for a given composition of the system, an increase in the average mean SnO2 crystallite size with the increasing the thermal treatment temperature is observed. The samples dried at room temperature and heated at 373 K and 473 K are also amorphous. Furthermore, for all systems and for each Miller index, the SnO2 crystallite size is the biggest after thermal treatment at 773 K. The higher load of platinum decreases the intensity of XRD reflexes in comparison to systems with lower metal content (Figures 2, 3). The cassiterite structure is not influenced by the addition of platinum except the 16.4% Pt on SnO2 system (Figure 3). It is believed that for other systems it is related to the small size of the platinum crystallites which cannot be detected [18].
Despite a high load of metal phase (up to 16%) no reflexes of platinum crystals or its compounds can be observed. This is probably a confirmation of high dispersion and stabilization of platinum in the tin dioxide gel structure.