Study On Preparation, Structure And Oxygen-sensing Property Of TiO₂ Porous Thin Films

In this paper the titanium dioxide sols were synthesized with tetrabutyl titanateas precursor , diethanolamine(DEA) and acetylacetone(AcAc) as complexing agent ,polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB) asorganic template. The porous films were prepared by sol-gel method . The formationmechanism of the TiO2 porous films and the factors influencing the surface structureof films are studied .Ordered structure is formed by assembling between TiO₂ colloid particles andthe template molecules, TiO₂ colloid particles acted with PEG by hydrogen bond andbridge oxygen , with CTAB by matching of charges in the interface. The porousstructure is formed after the template is decomposed when calcining the films.The diameter, amount and distribution of the pores on the surface of films arerelated with the molecular weight and content of PEG.. The pore diameter increasesand pore density decreases with increasing of the molecular weight of PEG.. Whenthe molecular weight is equal, the pore diameter increases with increasing of contentof PEG and the pore density reaches maximum at certain content. The porousstructure of TiO₂ film is also affected by the concentration of sols, amount ofcomplexing agent, ratio of H2O to Ti. Besides, the technology of coating andcalcining the films are also affecting the structure of the films.When DEA is used as complexing agent , the structure full of big and smallpores is simultaneously formed with increasing of content of CTAB. The porousstructure is damaged if content of CTAB is too much. When AcAc is used ascomplexing agent, the pore diameter and crack decrease with increasing of contentof CTAB.The relation between the porous structure and oxygen-sensing properties ofTiO2 films is studied. The lowest work temperature of porous TiO₂ films is 700℃ .Sensitivity and response speed are improved with the increasing of content of PEG.Sensitivity reaches 103 and response time reaches 0.12s at 800℃ respectively.The oxygen-sensing properties of porous TiO₂ films doped W6+ and Pd are alsostudied in this paper. The experiment results demonstrate that the work temperatureis reduced to 400℃, meanwhile the resistance-temperature character is improvedlargely after the surface of porous films is modified by Pd.