Thin film oxygen sensor
AssigneeNational Research Council of Canada
InventorMichael L. Post
Life of this patent
Estimating the term…
Abstract
An oxygen sensor is based on a thin film of a compound oxide supported on a substrate such as quartz. The compound oxide has a general formula ABO.sub.2.5+x, where A is an element of the lanthanum family, alkaline earth metal or their mixture, and B is a transition metal or a mixture of transition metals. X is a variable number, changing from about 0 to about 0.5 between the reversible oxygen-deplete and oxygen-rich forms of the oxide. In an elevated temperature and oxygen-containing atmosphere, the thin film can undergo reversible bulk oxidation resulting in a detectable change of its physical properties such as mass, optical transmissivity and electrical resistance.
Claims14
An oxygen sensor comprising:
- a thermally stable and chemically stable substrate,
- a thin uniform crystalline film of a nonstoichiometric compound oxide of the general formula ABO.sub.2.5+.sub.x supported on the substrate, wherein A is an element of the lanthanum family, an alkaline earth metal or a mixture thereof, B is a transition metal or a mixture of transition metals, and x is a number which defines bulk oxygen stoichiometry of the oxide and is variable between about 0 for an oxygen deplete and less than 0.5 for an oxygen saturated crystalline phase of the compound oxide, the film being of a thickness such that the compound oxide can undergo reversible bulk reaction with oxygen at an elevated temperature in an oxygen-containing atmosphere thereby undergoing a transition between the oxygen saturated and oxygen-deplete crystalline phases, and
- a detecting means for detecting a change in physical properties of said film, said change being a function of the varying bulk oxygen stoichiometry of the film.
A method of making an oxygen sensor, comprising
- providing a thermally stable and chemically stable substrate,
- applying onto the substrate in an oxygen-controlled atmosphere a uniform crystalline thin film of a non-stoichiometric compound oxide of the general formula ABO.sub.2.5+x, wherein A is an element of the lanthanum family, an alkaline earth metal or a mixture thereof, B is a transition metal or a mixture of transition metals, and x is a number which is variable between 0 for an oxygen deplete and less than 0.5 for an oxygen saturated crystalline phase of the compound oxide, the layer being of a thickness such that the compound oxide can undergo reversible bulk reaction with oxygen at an elevated temperature in an oxygen-containing atmosphere thereby undergoing transition between the oxygen saturated and oxygen-deplete crystalline phases, and
- providing a detecting means in association with the thin film for detecting a change in physical properties of said film.
Dependencies are inferred from the claim text.