Film of titanium dioxide containing silicon dioxide and a...

Details Film of titanium dioxide containing silicon dioxide and a... Film of titanium dioxide containing silicon dioxide and a...

1999-06-08

2001-08-28

Griffin, Steven P. (Department: 1754)

Chemistry of inorganic compounds

Oxygen or compound thereof

Metal containing

C423S613000, C428S428000, C428S432000, C427S167000, C427S397700

Reexamination Certificate

active

06280700

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a TiO
2
—SiO
2
film (a film of titanium dioxide containing silicon dioxide) giving a film of anatase by heat treatment, and a method of forming the same.
2. Description of the Prior Art
Titanium dioxide (TiO
2
) is known as a substance which can be used repeatedly as a catalyst having a high activity in environmental cleaning, for example, for decomposing the exhaust gases of automobiles and the nicotine of tobacco.
TiO
2
usually occurs in crystal form, and is classified by its structure into three types: rutile, brookite and anatase. It is easy to obtain rutile or brookite type TiO
2
by heat treating a film of amorphous TiO
2
at a temperature of 816° C. to 1040° C., but neither rutile nor brookite type TiO
2
has a very high catalytic power. Anatase type TiO
2
has a high catalytic activity, but is expensive, since it is mainly prepared by the hydrolysis of an organic titanium compound at a low temperature.
When TiO
2
is used as a catalyst, it is necessary to form it into a film, or fine particles to provide a large surface for the donation and acceptance of electrons, and it is necessary to heat treat such a film to ensure its adhesion to a substrate. Anatase type TiO
2
obtained by hydrolysis at a low temperature, however, is stable only at a temperature lower than 816° C., and easily changes to rutile type if heated at or above 816° C.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a film which can easily form by heat treatment anatase type TiO
2
which is stable even at a high temperature.
It is another object of this invention to provide a method of forming such a film.
It is still another object of this invention to provide a method of forming anatase type TiO
2.
As a result of our research work done for attaining the above objects, we, the inventors of this invention, have unexpectedly found that anatase type TiO
2
is precipitated if a film of TiO
2
containing SiO
2
is formed by depositing TiO
2
and SiO
2
simultaneously by sputtering method, and is heat treated. We have also found that it is stable even at or above the temperature of 816° C. at which the transformation of anatase to rutile normally occurs.
According to this invention, therefore, there is provided a film comprising TiO
2
and SiO
2.
According to another aspect of this invention, there is provided a method of forming a film containing TiO
2
and SiO
2
which comprises employing a target containing TiO
2
and SiO
2
, and depositing them simultaneously onto a substrate by sputtering method.
According to still another aspect of this invention, there is provided a method of forming a film containing TiO
2
and SiO
2
which comprises employing a source containing TiO
2
and SiO
2
, and heating them simultaneously to effect vapor deposition on a substrate.
According to a further aspect of this invention, there is provided a method of forming a film of anatase type TiO
2
containing SiO
2
which comprises heat treating a film containing TiO
2
and SiO
2
at a temperature of 200 ° C. to 1200° C.
A film containing TiO
2
and SiO
2
, or a TiO
2
—SiO
2
film comprises a mixture of TiO
2
and SiO
2
in molecular form.


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