The very fine oxide particles in TiO2-SnO2 system were prepared by the hydrolysis of titanium isopropoxide and tin isopropoxide in propanol solution. The following hydrolysis conditions were found to be necessary for the controlled synthesis of crystalline oxide precipitates, 1) process of water addition to propanol solution of metal isopropoxides, 2) the amount of water added to the metal isopropoxide solution, 3) hydrolysis time and aging time of the precipitate at boiling temperature (reflux time).
The crystalline TiO2 of anatase structure was precipitated by the hydrolysis of 0.05mol/l titanium isopropoxide with the amount of water 300 times more of the equivalent value for the oxide formation and the subsequent reflux, while the decrease of the amount of water to 70 times of the equivalent value resulted in the formation of amorphous TiO2. The crystalline phase of the precipitate changed depending on the amount of SnO2 in the system. The precipitate of the composition Ti0.9Sn0.1O2 was the mixture of anatase and rutile phases with the particle size of 50Å, and the increase of SnO2 to x=0.2 in Ti1-xSnxO2 solid solution gave the oxide precipitate composed of only rutile phase with the particle size of 23∼25Å.
On heating the precipitates, the grain of the anatase phase of TiO2 precipitates grew significantly at about 630°C, at which the phase transformation from anatase to rutile phase took place. On the precipitates of rutile structure, grain growth seemed to be more constrained and the neck growth between the grains became remarkable with an increase of the amount of SnO2.