Method of making a titanium dioxide oxygen sensor element by chemical vapor deposition

Claim 1

A method of making a titanium dioxide element which can be used as an oxygen sensing element, which method comprises the steps of: obtaining a substrate for supporting a titanium dioxide film; placing said substrate in a vacuum chamber; drawing a vacuum on said vacuum chamber; heating said substrate in said vacuum chamber to a temperature of 400°-700° C.; flowing a low pressure carrier gas over said heated substrate, said carrier gas containing 1-10% by volume of oxygen; adding a coating gas to said carrier gas for flowing over said substrate, said coating gas being an organometallic compound of titanium which is heat decomposable into a titanium dioxide coating phase and a heat volatilized phase, whereby titanium dioxide is coated onto said heated substrate, said coating gas and said carrier gas being at a total pressure from 100-200 Pa; continuing the addition of said coating gas to said carrier gas and flowing of said gases over said substrate until a titanium dioxide film of a required thickness in a range from 10-150 um is built up on said substrate at a rate of 0.1-5 um per minute; terminating said heating of said substrate and said flowing of said gases over said substrate when said titanium dioxide film of required thickness is coated on said substrate; and heating said coated substrate to a temperature in a range from 800°-1100° C. for period of 1-10 hours to transform said titanium dioxide film formed on said substrate to a rutile phase with a stable, porous microstructure.

Claim 2

A method of making a titanium dioxide element which can be used as an oxygen sensing element, which method comprises the steps of: obtaining a substrate for supporting a titanium dioxide film; placing said substrate in a vacuum chamber; drawing a vacuum on said vacuum chamber; heating said substrate in said vacuum chamber to a temperature of 400°-700° C.; flowing a low pressure carrier gas over said heated substrate, said carrier gas containing 1-10% by volume of oxygen; adding a coating gas to said carrier gas for flowing over said substrate, said coating gas being an organometallic compound of titanium which is heat decomposable into a titanium dioxide coating phase and a heat volatilized phase, whereby titanium dioxide is coated onto said heated substrate, said coating gas and said carrier gas being at a total pressure from 100-200 Pa; continuing the addition of said coating gas to said carrier gas and flowing of said gases over said substrate until a titanium dioxide film of a required thickness in a range from 10-150 um is built up on said substrate at a rate of 0.1-5 um per minute; terminating said heating of said substrate and said flowing of said gases over said substrate when said titanium dioxide film of required thickness is coated on said substrate; and heating said coated substrate to a temperature in a range from 800°-1100° C. for period of 1-10 hours to transform said titanium dioxide film formed on said substrate to a rutile phase with a stable, porous microstructure.

Claim 5

A method of making a titanium dioxide element which can be used as an oxygen sensing element, which method comprises the steps of: obtaining a substrate for supporting a titanium dioxide film; placing said substrate in a vacuum chamber; drawing a vacuum on said vacuum chamber; heating said substrate in said vacuum chamber to a temperature of 550°-650° C.; flowing a low pressure carrier gas over said heated substrate, said carrier gas containing 3-7% by volume of oxygen; adding a coating gas to said carrier gas for flowing over said substrate, said coating gas being tetraisopropyl titanate which is heat decomposable into a titanium dioxide coating phase and a heat volatilized phase, whereby titanium dioxide is coated onto said heated substrate, said coating gas and said carrier gas being at a total pressure from 100-200 Pa; continuing the addition of said coating gas to said carrier gas and flowing of said gases over said substrate until a titanium dioxide film of a required thickness in a range from 10-150 um is built up on said substrate at a rate of 0.1-5 um per minute; terminating said heating of said substrate and said flowing of said gases over said substrate when said titanium dioxide film of required thickness is coated on said substrate; and heating said coated substrate to a temperature in a range from 800°-1100° C. for period of 1-10 hours to transform said titanium dioxide film formed on said substrate to a rutile phase with a stable, porous microstructure.

Claim 6

A method of making a titanium dioxide element which can be used as an oxygen sensing element, which method comprises the steps of: obtaining a substrate for supporting a titanium dioxide film; placing said substrate in a vacuum chamber; drawing a vacuum on said vacuum chamber; heating said substrate in said vacuum chamber to a temperature of 550°-650° C.; flowing a low pressure carrier gas over said heated substrate, said carrier gas containing 3-7% by volume of oxygen; adding a coating gas to said carrier gas for flowing over said substrate, said coating gas being tetraisopropyl titanate which is heat decomposable into a titanium dioxide coating phase and a heat volatilized phase, whereby titanium dioxide is coated onto said heated substrate, said coating gas and said carrier gas being at a total pressure from 100-200 Pa; continuing the addition of said coating gas to said carrier gas and flowing of said gases over said substrate until a titanium dioxide film of a required thickness in a range from 10-150 um is built up on said substrate at a rate of 0.1-5 um per minute; terminating said heating of said substrate and said flowing of said gases over said substrate when said titanium dioxide film of required thickness is coated on said substrate; and heating said coated substrate to a temperature in a range from 800°-1100° C. for period of 1-10 hours to transform said titanium dioxide film formed on said substrate to a rutile phase with a stable, porous microstructure.