Patent Application
20090007637
This Application claims priority of Taiwan Patent Application No. 096124635, filed on Jul. 6, 2007, the entirety of which is incorporated by reference herein.
1. Field of the Invention
The present invention relates to a gas sensor, and in particular relates to an oxygen sensor.
2. Description of the Related Art
Conventionally, thickness of the electrolyte layer 13 effects sensitivity of the oxygen sensor 10. Sensitivity of the oxygen sensor 10 increases when the electrolyte layer 13 is thinner. However, the electrolyte layer 13 is fragile, thus it is difficult to further decrease thickness. Additionally, modifying thickness of the electrolyte layer 13 increases costs.
A detailed description is given in the following embodiments with reference to the accompanying drawings.
In one embodiment, a gas sensor is provided. The gas sensor comprises a substrate, a first electrode, a second electrode, a power source and a current meter. The substrate comprises a planar surface, wherein the substrate is made of ion-conductive material, proton-conductive material or electron-conductive material. The first electrode is formed on the planar surface. The second electrode is formed on the planar surface, wherein a gap is formed between the first electrode and the second electrode. The power source is electrically connected to the first electrode and the second electrode, wherein the power source provides a voltage to the first electrode and the second electrode. The current meter is electrically connected to the first electrode and the second electrode to measure a limit current passing the first electrode and the second electrode.
In a modified embodiment, a gas detection method is provided, which comprises the following steps. First, the gas sensor is provided. Next, a gas is provided and contacts the gas sensor. Then, the voltage is applied to the first electrode and the second electrode with the electronic source, wherein the gas is ionized at the first electrode to generate a plurality of ions, protons or electrons, and the ions, protons or electrons permeate the substrate to conduct the first electrode and the second electrode. Finally, the limit current passing the first electrode and the second electrode is measured by the current meter.
In the embodiment of the invention, sensitivity of the gas sensor can be modified by modifying the gap which is between the first electrode and the second electrode. The gas scale can be easily controlled. Therefore, the invention provides a highly sensitive gas sensor through a cheaper and more convenient method.
The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
The first electrode 110 and the second electrode 120 contacts oxygen in the air. When the power source 140 applies the voltage, oxygen is ionized into oxygen ions at the first electrode 110. The oxygen ions partially permeate into the substrate 130, and bring the electrons to the second electrode 120. The second electrode 120 reduces the oxygen ions into oxygen. When environmental oxygen consistency is high, the action mentioned above speeds up, electrons traveling from the first electrode 110 to the second electrode 120 increase, and the limit current increases. Therefore, by measuring the limit current with the current meter 150, the gas sensor 100 of the embodiment may define environmental oxygen consistency.
The sensitivity of the gas sensor 100 can be modified by controlling the lateral diffusion gap 101 of the ion, proton and/or electron. Because the lateral diffusion gap 101 can be easily controlled, a highly sensitive gas sensor 100 can be easily realized.
The substrate 130 can be made by a thick film process, such as a screen print, dry press, inject or scrape process. The substrate 130 also can be made by a thin film process of Micro Electro-Mechanical Systems, such as a lift-off or etching process.
With reference to
The ion-conductive material, proton-conductive material or electron-conductive material can comprise cerium oxide or zirconium oxide mixed with positive ion with +2 or +3 charges. The ion-conductive material, proton-conductive material or electron-conductive material can also be LaMo2O9 or Perovskite.
The first electrode 110 and the second electrode 120 can comprise the following materials: (a) metal materials such as Pt, Au, Pd, Rh, Ir, Ru, Os, Ni, Co and Fe which can easily electrical-chemical react with oxygen; (b) Perovskite ceramics such as LaSrMnO3 and LaSrCoFeO3, which can easily electrical-chemical react with oxygen; (c) a combined material comprising the metal materials and the Perovskite ceramics mentioned above and zirconium oxide to provide ion-conduction and electron-conduction; (d) a second phase material for resisting carbonization, poisoning or vulcanization, such as copper or cerium oxide.
In a sintering process and a heat treatment of the gas sensor of the invention, an electric furnace, atmosphere furnace, microwave sintering furnace, laser annealing and heat press are utilized to calcine elements and sinter (jointly or separately) the electrolyte and the interdigital electrodes. When a thin film process is utilized to sinter and heat-treat the gas sensor, the sintering temperature thereof is about 600° C. to 800° C. When a thick film process is utilized to sinter and heat-treat the gas sensor, the sintering temperature thereof is about 1300° C. to 1600° C.
The gas diffusion layer can comprise the following materials: (a) magnesium aluminate spinel; (b) lanthanum aluminum oxide; (c) a second phase material for resisting carbonization, poisoning or vulcanization, such as copper or cerium oxide.
The gas sensor of the embodiments of the invention can be produced by a planar process or a semiconductor process to decrease costs and be mass produced.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
| Number | Date | Country | Kind |
|---|---|---|---|
| TW96124635 | Jul 2007 | TW | national |
