CN1862255A - Gas sensor - Google Patents
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- CN1862255A CN1862255A CN 200610081718 CN200610081718A CN1862255A CN 1862255 A CN1862255 A CN 1862255A CN 200610081718 CN200610081718 CN 200610081718 CN 200610081718 A CN200610081718 A CN 200610081718A CN 1862255 A CN1862255 A CN 1862255A
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Abstract
According to one embodiment, the gas sensor includes a porous plate-like sintered body comprising trisilicon tetranitride needle crystals; two first catalyst metal thin films and one second catalyst metal thin film, formed on one surface of the plate-like sintered body in a non-contacted state with each other; oxygen ion-conductive solid electrolyte thin films formed on the respective surface; a surface layer thin film formed on the respective surfaces, so that a first measurement part, a second measurement part and a third measurement part are constituted; and a glass sealing layer comprising silicon oxide, formed on other surface of the porous plate-like sintered body, a surface other than the surface of the porous plate-like sintered body having the first catalyst metal thin film and the second catalyst metal thin film formed thereon, and a side of the first measurement part and the second measurement part.
Description
Technical field
The present invention relates to a kind of gas sensor that is used for measuring contained nitrogen oxide of burnt gas and oxygen content.
Background technology
As the gas sensor that is used for measuring contained nitrogen oxide of burnt gas and oxygen content, for example as JP-A-10-90220 Jap.P. 2885336 and Kogyo Kanetsu (industrial heating) vol.41, No.6, pp.31-36 is described, known have a sensor with following structure, this structure comprises and is used to find time first Room of oxygen and second Room relevant with the measurement of nitrogen oxide, this sensor is measured oxygen concentration in first Room, and reduce oxygen concentration in the measurement gas simultaneously to about 10ppm, in second Room, pass through the reduction decomposition nitrogen oxide, detect the oxygen that is generated by suction in a similar manner, and measure the concentration of nitrogen oxide gas.These sensors are to produce by the thin plate that zirconia (for for simplicity hereinafter to be referred as " the YSZ ") sintered body of yttria has been added in welding.
In addition, for example described as JP-A-2000-62077, known have a kind of like this sensor, and wherein, substrate comprises and is formed at silicon nitride (Si
3N
4) YSZ film on (hereinafter to be referred as " silicon nitride ") porous sintered body, wherein said porous sintered body comprises needle-shaped crystals.
Sensor with this structure has realized shortening heating-up time that is caused by the decline of measurement temperature and the target of improving resistance to sudden heating.
But, JP-A-10-90220, Jap.P. 2885336 and Kogyo Kanetsu (industrial heating) vol.41, No.6, the sensor described in the pp.31-36 has all used the slab material.As a result, need under 700 ℃ or higher temperature, to heat, will to spend 15 minutes in order elevating the temperature or the longer time, in addition, will spend 30 minutes or longer up to obtaining to stablize output.In addition, the sintered body structure of welding has at welding portion usually owing to heat up repeatedly and cool off and the problem that may break.
Above-mentioned conventional sensors constitutes by two parts, and a part is used for oxygen depleted, and a part is used for measuring N Ox gas.Therefore, perhaps there is the dispersion (scattering in exhaustion) exhaust in the oxygen if previous stage is not fully found time, will cause the measuring error of NOx in NOx measure portion remnant oxygen, and the measuring accuracy problem on the ppm magnitude can take place.
Sensor described in the JP-A-2000-62077 relates to the gaseous diffusion from thickness direction.So, not enough as the function of gas diffusion layers, and the problem that has quantified precision to descend.
Summary of the invention
The present invention makes in view of the defective of prior art.
Therefore, the object of the present invention is to provide a kind of gas sensor, it can shorten the rise time of sensor, reduces heating-up temperature and is used to prevent that the welding portion of sintered body from breaking, and improve the precision that quantizes.
According to one embodiment of present invention, provide a kind of gas sensor, having comprised:
The porous tabular sintered body that comprises the silicon nitride needle-shaped crystals;
Begin to be formed at the first catalyst metals film and second catalyst metals film that comprises second catalyst metals that comprises first catalyst metals on the described tabular sintered body from the introducing side of measurement gas, make described first catalyst metals film and the described second catalyst metals film be in not contacted each other state;
Be formed at the oxygen ionic conductive solid electrolytic thin-membrane on the respective surfaces of described first catalyst metals film and the described second catalyst metals film;
Be formed at each lip-deep superficial layer film that comprises described first catalyst metals of each ion conductive solid electrolyte film, be in described first catalyst metals film and the not contacted each other state of the described second catalyst metals film, thereby constitute first measure portion and the 3rd measure portion; And
The glass seal layer that comprises monox, it is formed at other surfaces of described porous tabular sintered body, described porous tabular sintered body and is formed with on it on side of surface outside the surface of described first catalyst metals film and the described second catalyst metals film and described first measure portion and described the 3rd measure portion.
According to one embodiment of present invention, provide a kind of gas sensor, having comprised:
The porous tabular sintered body that comprises the silicon nitride needle-shaped crystals;
Begin to be formed at lip-deep two the first catalyst metals film and second catalyst metals films that comprise second catalyst metals that include first catalyst metals of described tabular sintered body from the introducing side of measurement gas, make described first catalyst metals film and the described second catalyst metals film be in not contacted each other state;
Be formed at the oxygen ionic conductive solid electrolytic thin-membrane on the respective surfaces of described two first catalyst metals films and described one second catalyst metals film;
Be formed at each lip-deep superficial layer film that comprises described first catalyst metals of each ion conductive solid electrolyte film, be in described two first catalyst metals films and the not contacted each other state of the described second catalyst metals film, thereby constitute first measure portion, second measure portion and the 3rd measure portion; And
The glass seal layer that comprises monox, it is formed at other surfaces of described porous tabular sintered body, described porous tabular sintered body and is formed with on it on side of surface outside the surface of described first catalyst metals film and the described second catalyst metals film and described first measure portion, described second measure portion and described the 3rd measure portion
The output of described second measure portion is added in the output of described first measure portion, and deducts the output of described second measure portion from the output of described the 3rd measure portion.
Gas sensor according to the present invention has used the oxygen ionic conductive solid electrolytic thin-membrane in first measure portion, the 3rd measure portion and optional second measure portion.This makes it can reduce heating-up temperature, and can measure oxygen contained in the burning gases and every kind concentration of nitrogen oxide in the very short rise time.
In gas sensor of the present invention, comprise that the porous tabular sintered body of silicon nitride needle-shaped crystals is used as substrate, and on substrate, form first measure portion, the 3rd measure portion and optional second measure portion.As a result, these measure portion enter in the porous tabular sintered body, prevent each measure portion thus and as peeling off between the porous aciculiform sintered body of substrate etc.
Glass seal layer is provided on given position.This has prevented the gaseous diffusion of the part outside first measure portion, the 3rd measure portion and (optionally) second measure portion.As a result, can improve the precision of quantification.
In addition,, duplicate measurements can be stablized, and power consumption can be further greatly reduced according to sensor of the present invention by above-mentioned structure.
In addition, when providing first measure portion, second measure portion and the 3rd measure portion, following benefit is arranged.In first measure portion by the solid electrolyte film oxygen depleted, but oxygen residual the amount of 10 to tens ppm.But, by measure remaining oxygen in second measure portion, can improve precision in the NOx gasmetry of the precision of the oxygen measurement of the first measurement section office and the 3rd measurement section office.In other words, compare, can also improve the precision of NOx gasmetry with only providing the embodiment of first measure portion with the 3rd measure portion.
Description of drawings
Fig. 1 is the cross-sectional view that illustrates according to an embodiment of gas sensor of the present invention.
Fig. 2 is the cross-sectional view that illustrates according to another embodiment of gas sensor of the present invention.
Fig. 3 is a curve map, shows in example in the relation between content of nitrogen dioxide (ppm) and the electric current output (mA) under the situation of using sensor (first sensor 1a) shown in Figure 1.
Fig. 4 is a curve map, shows in example in the relation between content of nitrogen dioxide (ppm) and the electric current output (mA) under the situation of using sensor (the second sensor 1b) shown in Figure 2.
Embodiment
Hereinafter describe the present invention in detail.
In sensor 1, substrate 2 comprises porous tabular sintered body (porous plate-like sinteredbody).This porous tabular sintered body is by sintering silicon nitride (Si
3N
4) acquisition of (following be called for the sake of simplicity " SiN ") needle-shaped crystals, have the structure of intricate ground of many SiN needle-shaped crystals weave in.
This porous tabular sintered body has preferably from 30 to 80% porosity.Less than 30% o'clock, it is not enough that the gas penetration potential of sintered body is tending towards in porosity.On the other hand, surpass at 80% o'clock in porosity, such sintered body does not have enough physical strengths, and in addition, gets inadequately in the quantitative change of first and second catalyst metals of sintered body upper support.As a result, sensor that might gained can not show the performance of expectation.
Hole in the porous tabular sintered body (pore) has the average pore size of preferred from 0.01 to 50 μ m, more preferably 0.05 to 1 μ m.During less than 0.01 μ m, it is not enough that the gas penetration potential of this sintered body is tending towards in the average pore size.On the other hand, when the average pore size surpassed 50 μ m, the physical strength of this sintered body was tending towards reducing.
The length breadth ratio of SiN needle-shaped crystals (aspect ratio) is preferably 3 to 30.When length breadth ratio less than 3 the time, it is not enough that the physical strength of crystal is tending towards.On the other hand, length breadth ratio can surpass 30, but might be difficult to produce this crystal.Therefore, length breadth ratio on be limited to 30 just enough.
The minor axis of SiN needle-shaped crystals (minor axis) length is preferably 0.05 to 10 μ m, more preferably 0.1 to 1 μ m.In minor axis length during less than 0.05 μ m, the weakened of needle-shaped crystals, and the trend that reduces the crystal overall mechanical strength is arranged.On the other hand, when minor axis length surpassed 10 μ m, binding site reduced between the needle-shaped crystals, and the trend of the overall mechanical strength that reduces crystal is arranged.
The thickness of porous tabular sintered body is preferably 0.1 to 10mm.During less than 0.1mm, the physical strength of sintered body reduces, and exists this porous tabular sintered body can not drop into the possibility of actual use at thickness.On the other hand, when thickness surpassed 10mm, the diffusion of gas or supply surpassed measurement capability, and might cause impairment to measuring accuracy.
The porous tabular sintered body is preferably such, by use particle diameter be 0.1 to 0.01 μ m alumina powder polishing (buff polishing) its go up the surface of formation catalyst metals film.By this polishing, obtained smooth surface, and can form thin and fine and close solid electrolyte film.When the particle diameter of aluminium oxide surpassed 0.1 μ m, the surface of sintered body became coarse, does not obtain enough polishing effects.On the other hand, during less than 0.01 μ m, polishing efficiency descends, thereby impracticable at the aluminium oxide particle diameter.
Can be by several different methods production porous tabular sintered body.For example, can use the method for in the international open No.WO1994/27929 of PCT, describing.This method comprises: as required, molded alpha-silicon nitride powders, this powder have the potpourri that contains such as the rare earth element of mixing with it of yttrium, then under nitrogen containing atmosphere under 1500 to 2100 ℃ temperature the mouldings of heat treated gained.By this method, can precipitate and comprise β-Si
3N
4Needle-shaped crystals, so can generate porous body with high porosity.
In sensor 1, the first measure portion 3a comprises layered structure, this layered structure makes up by following steps: form the first catalyst metals film 5a that comprises first catalyst metals on a surface of substrate 2, on the surface of the first catalyst metals film 5a, form oxygen ionic conductive solid electrolytic thin-membrane 6a, on the surface of oxygen ionic conductive solid electrolytic thin-membrane 6a, form the superficial layer film 7a that comprises first catalyst metals then, make the superficial layer film 7a and the first catalyst metals film 5a not contact each other.
In sensor 1, the 3rd measure portion 4 comprises layered structure, this layered structure makes up by following steps: form the second catalyst metals film 8 that comprises second catalyst metals on a surface of substrate 2, on the surface of the second catalyst metals film 8, form the oxygen ionic conductive solid electrolytic thin-membrane 6c identical with oxygen ionic conductive solid electrolytic thin-membrane 6a, on the surface of oxygen ionic conductive solid electrolytic thin-membrane 6c, form the superficial layer film 7c identical then, make the superficial layer film 7c and the second catalyst metals film 8 not contact each other with superficial layer film 7a.
In second sensor 2, the second measure portion 3b comprises layered structure, this layered structure makes up by following steps: form the first catalyst metals film 5b that comprises first catalyst metals on a surface of substrate 2, on the surface of the first catalyst metals film 5b, form the oxygen ionic conductive solid electrolytic thin-membrane 6b identical with oxygen ionic conductive solid electrolytic thin-membrane 6a, on the surface of oxygen ionic conductive solid electrolytic thin-membrane 6b, form the superficial layer film 7b identical then, make the superficial layer film 7b and the first catalyst metals film 5b not contact each other with superficial layer film 7a.
The first catalyst metals film 5a among the first sensor 1a, perhaps the first catalyst metals film 5a and the 5b among the second sensor 1b means the film that comprises above-mentioned first catalyst metals.The example of first catalyst metals comprises platinum, nickel and platinum alloy.Wherein, preferably use platinum.The second catalyst metals film 8 in the sensor 1 means the film that comprises above-mentioned second catalyst metals.The example of second catalyst metals comprises rhodium, ruthenium and platinum-rhodium alloy.Wherein, preferably use rhodium.
The method that forms the first catalyst metals film 5a (or 5a and 5b) or the second catalyst metals film 8 on substrate 2 comprises by physical deposition etc. carries out deposit.Be formed at the first catalyst metals film 5a (perhaps 5a and 5b) on the substrate 2 or the second catalyst metals film 8 along forming by these methods, thereby form concavo-convex (unevenness) shape as the needle-shaped crystals on the surface portion of the porous tabular sintered body of substrate 2.Particularly, form the first catalyst metals film 5a (or 5a and 5b) or the second catalyst metals film 8 with the form that enters as the porous tabular sintered body of substrate 2.The result, improved the adhesion between the first catalyst metals film 5a (perhaps 5a and 5b) or the second catalyst metals film 8 and the substrate 2, this can prevent peeling off between the first catalyst metals film 5a (or 5a and 5b) or the second catalyst metals film 8 and the substrate 2, it breaks or the like.
The example of physical deposition comprises vacuum deposition, sputter and ion plating.The vacuum deposition meaning is such method: utilize in a vacuum resistor or electron gun with heating evaporation such as metal so that deposit, and on substrate, condense them, form coated film thus.The sputter meaning is such method: clash into target with energetic ion, with the neutral atom of knocking-on formation target, accumulating neutral atom on the substrate relatively, and forming coated film.
Ion plating is such method: wherein, the part particle that ionization is evaporated in vacuum deposition to be increasing its kinergety, then can improve the film quality of formed film, such as clinging power or compactness.The example of ion plating comprises many cathode primary electron irradiation method, high frequency excitation method, hollow cathode method, ion beam method, priming reaction sedimentation and arc ions electrochemical plating.
Formation makes them not contact each other by the first catalyst metals film 5a (or 5a and 5b) or the second catalyst metals film 8 that said method forms.By making them be in not contact condition, the first measure portion 3a (or the first measure portion 3a and the second measure portion 3b) is not contacted with the 3rd measure portion 4.By this structure, can carry out independently at the first measure portion 3a place measurement, in the measurement at the 3rd measure portion 4 places, and alternatively, the measurement at the second measure portion 3b place.
Be formed at the film that oxygen ionic conductive solid electrolytic thin-membrane 6a (or 6a and 6b) on the respective surfaces of the first catalyst metals film 5a (or 5a and 5b) and the second catalyst metals film 8 and 6c mean the solid electrolyte that comprises that oxygen conduction (oxygen ion conductivity) is high.The example of solid electrolyte comprises zirconia (ZrO
2) base, cerium oxide (CeO
2) base and lanthanum gallate (LaGaO
3) basic solid electrolyte.The example of the solid electrolyte of zirconia base comprises and contains zirconic solid solution, is added with yttria, gadolinium oxide, samarium oxide etc. in this solid solution.The example of the solid electrolyte of cerium oxide base comprises the solid solution that contains cerium oxide, is added with yttria, gadolinium oxide, samarium oxide etc. in this solid solution.The example of LaGaO 3 based solid electrolyte comprises the solid solution that contains lanthanum gallate, wherein is added with strontium oxide strontia, magnesium oxide etc.
A little less than the physical strength of oxygen ionic conductive solid electrolytic thin-membrane 6a (or 6a and 6b) and 6c, but have high ionic conductivity and can form film.Therefore,, can greatly reduce its size under about 400 ℃ low temperature, and the time of rising temperature and stable output can be shortened within 1 minute even sensor according to the present invention also can be worked.
Form on the surface of the first catalyst metals film 5a (or 5a and 5b) and on the surface of the second catalyst metals film 8 respectively oxygen ionic conductive solid electrolytic thin-membrane 6a (or 6a and 6b) and 6c can by with the method for the formation first catalyst metals film 5a (or 5a and 5b) and the second catalyst metals film 8 in same physical deposition method carry out.
The lower thickness limit of the first catalyst metals film 5a (or 5a and 5b) and the second catalyst metals film 8 is preferred 0.01 μ m.During less than 0.01 μ m, be difficult to form continuous films at thickness, and have can not supplies electrons trend.On the other hand, the upper limit of film thickness all is preferably 0.5 μ m, and 0.1 μ m or littler more preferably.Surpass the space that the thickness of 0.5 μ m results in blockage in comprising the substrate of needle-shaped crystals, and the problem that exists gaseous diffusion to be restricted.This thickness is more preferably in 0.03 to 0.07 mu m range, especially at about 0.05 μ m.
The lower thickness limit of oxygen ionic conductive solid electrolytic thin-membrane 6a (or 6a and 6b) and 6c all is preferably 0.5 μ m.During less than 0.5 μ m, in the oxygen ionic conductive solid electrolytic thin-membrane, produce too many pin hole (pinhole) at thickness, and be in the level that to ignore from the gaseous diffusion of pin hole.As a result, exist the big problem of error change of measurement data.On the other hand, the upper thickness limit of oxygen ionic conductive solid electrolytic thin-membrane all is preferably 20 μ m, more preferably 10 μ m.When thickness surpassed 20 μ m, the stress in the oxygen ionic conductive solid electrolytic thin-membrane was excessive, caused the resistance to sudden heating of film to reduce.So, exist the trend that the thermal cycle life of sensor reduces.This thickness is more preferably in 3 to 7 mu m ranges, especially at about 5 μ m.
Comprise that the glass seal layer 9 as the monox of principal ingredient is formed on another surface of substrate 2, be the surface that is formed with on it outside substrate surface of the first catalyst metals film 5a (or 5a and 5b) and the second catalyst metals film 8, this glass seal layer 9 also is formed on the side of the first measure portion 3a, second measure portion (with regard to the second sensor 1b) and the 3rd measure portion 4.By forming glass seal layer, gaseous diffusion can be only limited to the gaseous diffusion from superficial layer film 7a (or 7a and 7b) and 7c, and can make the layer of decision rate of diffusion complete.The glass that comprises monox that is used for glass seal layer 9 comprises borosilicate base glass etc.
Operation according to sensor 1 of the present invention (the first sensor 1a and the second sensor 1b) is below described.
In sensor 1 according to the present invention, first catalyst metals film 5a among the first measure portion 3a and superficial layer film 7a are equipped with inlead (lead-in wires) (not shown) respectively, are applied in voltage on it.Similarly, with regard to the second sensor 1b, the first catalyst metals film 5b and superficial layer film 7b among the second measure portion 3b are equipped with the inlead (not shown) respectively, are applied in voltage on it.
In addition, in sensor 1 according to the present invention, the second catalyst metals film 8 and superficial layer film 7c in the 3rd measure portion 4 are equipped with the inlead (not shown) respectively, are applied in voltage on it.When the ion that produces from gas 11 flows into the first measure portion 3a, just generate electric current.Can measure the influx of oxygen from current value, the result can calculate the amount of oxygen in the gas 11.
The first catalyst metals film 5a among the first measure portion 3a (concerning second sensor, being the first catalyst metals film 5a among the first measure portion 3a and the first catalyst metals film 5b among the second measure portion 3b) causes that nitrogen dioxide changes into nitric oxide production reaction.But, further reaction can not take place, and usually with regard to the gas that uses air for example, can not relate to the reaction of oxygen.As a result, the amount of oxygen that in the first measure portion 3a, measures corresponding to gas 11 in contained amount of oxygen.
On the other hand, the second catalyst metals film 8 in the 3rd measure portion 4 causes nitrogen monoxide to change into the reaction of nitrogen and oxygen.As a result, the amount of oxygen that records in the 3rd measure portion 4 is contained amount of oxygen and the amount of oxygen sum that generates from nitrogen monoxide in the gas 11.
Therefore, can calculate the amount of oxygen that produces from nitrogen monoxide from the measurement data in measurement data the first measure portion 3a and the 3rd measure portion 4.As a result, contained nitric oxide production amount can access calculating in the gas 11.
But, there is such possibility, that is: since the value that is supplied to the dispersion of initial oxygen concentration in the gas of sensor 1 to cause measuring among the first measure portion 3a disperse, perhaps cause and will be sent to the dispersion of the residual oxygen tolerance in the gas 11 of the 3rd measure portion 4, this gives, and the measurement to NOx has brought error in the 3rd measure portion 4.
In view of this, can further improve measuring accuracy in the first measure portion 3a and the 3rd measure portion 4 by the amount of measuring the remnant oxygen among the first measure portion 3a at the second measure portion 3b place.
To the representative measure method of sensor 1 be described.Particularly, Pt well heater 12 is fixed on the bottom of sensor 1, promptly with the surperficial facing surfaces with the first measure portion 3a, the second measure portion 3b and the 3rd measure portion 4, by curing, utilize well heater that sensor 1 is heated to 250 to 600 ℃ temperature, be preferably 350 to 500 ℃.This can be at the first measure portion 3a (concerning the second sensor 1b, be the first measure portion 3a and the second measure portion 3b) and the 3rd measure portion 4 in cause reaction, can also improve oxygen ionic conductive solid electrolytic thin- membrane 6a, 6b in first measure portion 3a (concerning second sensor, being the first measure portion 3a and the second measure portion 3b) and the 3rd measure portion 4 and the oxygen electric conductivity of 6c.
The gas 11 that contains nitrogen oxide to be measured is injected into from the edge of substrate 2.Portion gas 11 is discharged into the outside then by the first measure portion 3a, and other parts of gas 11 are discharged into the outside then by the second measure portion 3b.
In first sensor 1a, calculate oxygen content in the gas 11 by the first measure portion 3a as mentioned above by making gas 11.In addition, remain in amount that concentration in the gas 11 is tens ppm or lower oxygen and the amount of oxygen sum that produces from nitrogen oxide among the first measure portion 3a by making gas 11 as mentioned above by the 3rd measure portion 4, calculating.Might calculate the amount of the nitrogen oxide in the gas 11 from these calculate, this amount becomes the concentration of hundreds of ppm.
In the second sensor 1b, calculate oxygen content in the gas 11 by the first measure portion 3a as mentioned above by making gas 11.Calculate amount of oxygen remaining in the gas 11 by making gas 11 flow through the second measure portion 3b.In addition, by making gas 11 flow through the amount of oxygen sum that the 3rd measure portion 4 is calculated oxygen content and produced from nitrogen oxide.Particularly, be added to the amount of calculating oxygen in the output of the first measure portion 3a by output, and calculate the amount of nitrogen oxide by the output that the output from the 3rd measure portion deducts second measure portion the second measure portion 3b.Might calculate the amount of the nitrogen oxide the gas 11 from these calculating.Therefore, the oxygen content of delivering in the gas 11 of the 3rd measure portion 4 is measured in the second measure portion 3b, so just can revise the measuring error of amount of the oxygen in the first measure portion 3a and the measuring error of the nitrogen oxide amount in the 3rd measure portion 4.By like this, compare with the situation of the first sensor 1a of the 3rd measure portion 4 with only being equipped with the first measure portion 3a, can further improve the measuring accuracy of nitrogen oxide.
By describing the present invention in more detail, still know that very the present invention should not be considered as being subject to this with reference to following example.
The manufacture method of sensor:
Sensor 1a as shown in Figure 1 and sensor 1b as shown in Figure 2 make according to following method.
The production of substrate 2:
Prepare the silicon nitride sintered body according to the method described in the international open No.W01994/27929 of PCT.Particularly, molded assistant (molding assistant) is added to comprise that mean grain size is 0.3 μ m (specific surface area 11m
2/ g) α-Dan Huagui (α-Si
3N
4) in the silicon nitride powder as principal ingredient, and at 20kg/cm
2Pressure under with being of a size of the molded synthetic mixture of mould of 100mm * 100mm.The mechanograph two hours of 1800 ℃ of following thermal treatment gained under 4 atmospheric pressure obtains the silicon nitride sintered body.The sintered body that is obtained has the thickness of 0.5mm, the average pore size of 0.1 μ m and 40% porosity.
The silicon nitride sintered body that obtains is like this cut into the sheet of 5mm * 10mm, and will cut into slices is used as substrate 2.
The formation of the first catalyst metals film 5a (being first catalyst film 5a and the 5b for the second sensor 1b):
The substrate 2 of above acquisition is fixed to substrate holder, this substrate holder had carried out the groove identical with substrate shape to be handled, and will have square window (window of 4mmsquare) (is two windows for the second a sensor 1b) mask of 4mm then and be fixed to a surface of substrate 2.On window portion, form the Pt metal film by spatter film forming method, so that with the thickness of 0.05 μ m and there is not the surface that embedded hole unoccupied place (without embedding pores) covers the needle-shaped crystals that constitutes substrate 2.So just formed the first catalyst metals film 5a (with regard to the second sensor 1b, being non-touching each other first catalyst metals film 5a and the 5b).
The formation of the second catalyst metals film 8:
The substrate 2 that is formed with the first catalyst metals film 5a (being the first catalyst metals film 5a and 5b) on it for the second sensor 1b be fixed to carried out substrate holder that groove handles with the shape identical with substrate 2 in, remove the mask that is used to form the Pt metal film, and will have the new mask that is of a size of the square window of 4mm be fixed in abutting connection with the first catalyst metals film 5a (for the second sensor 1b, be meant in abutting connection with the position of the first catalyst metals film 5b and the opposite side of the first catalyst metals film 5a) the position, and not overlapping with the first catalyst metals film 5a (being the first catalyst metals film 5b with regard to the second sensor 1b).On window portion, form the Rh metal film by spatter film forming method, so that with the thickness of 0.05 μ m and there is not the surface that the embedded hole unoccupied place covers the needle-shaped crystals that constitutes sintered body.So just formed the second catalyst metals film 8.
The formation of oxygen ionic conductive solid electrolytic thin-membrane 6a (is oxygen ionic conductive solid electrolytic thin- membrane 6a and 6b for the second sensor 1b) and 6c:
When the substrate 2 that will be used to form the second catalyst metals film 8 is fixed to the substrate holder that carried out the groove processing with the shape identical with substrate, remove the new mask that is formed with the Rh metal film, and be fixed for forming solid electrolyte film, have two new masks that all have the window of the square opening of 3mm, make two openings on the respective surfaces of the part (the second catalyst metals film 8) of part (the first catalyst metals film 5a (being first catalyst metals film 5a and the 5b for the second sensor 1b)) that forms the Pt metal film and formation Rh metal, mate.
The assembly that comprises substrate holder of gained is arranged in the film-forming apparatus that utilizes KrF excimer laser ablation method.
To be mixed with the Gd of 5mol% individually
2O
3The CeO of powder
2Powder is put into mould, and is undertaken moldedly by oil pressure, is 20mm to obtain diameter, and thickness is the target of 5mm.This target is arranged on precalculated position in the film-forming apparatus.
The excimer laser that is output as 600mJ/ pulse and repetition frequency and is 5Hz is converged by convex lens, then with this this target of the excimer laser irradiation that converges.Vacuum tightness during the formation film is 1.33 * 10
-2The oxygen atmosphere of Pa.At the initial period underlayer temperature that forms film is room temperature, and its progress of being controlled to form along with film is raise gradually.Final underlayer temperature is 700 ℃, in initial 1 hour temperature is elevated to 700 ℃ in the time that forms film.After the temperature of 700 ℃ of arrival, temperature is kept constant.Total film formation time of solid electrolyte is 3 hours.Form solid electrolyte film being used to measure on the quartz substrate of film thickness, and with the thickness of stylus section plotter (stylus profiler) MEASUREMENTS OF THIN.Found that thickness is 5 μ m.So just formed oxygen ionic conductive solid electrolytic thin-membrane 6a (is oxygen ionic conductive solid electrolytic thin- membrane 6a and 6b for the second sensor 1b) and 6c.
The formation of superficial layer film 7a (for the second sensor 1b, being superficial layer film 7a and 7b) and 7c:
When being formed with oxygen ionic conductive solid electrolytic thin-membrane 6a (for the second sensor 1b, being oxygen ionic conductive solid electrolytic thin- membrane 6a and 6b) on it and the substrate 2 of 6c be fixed to the substrate holder that carried out the groove processing with the shape identical with substrate, remove the mask that is used to form solid electrolyte film, and fixedly have the new mask that two (or three) all have the window of the square opening of 2.5mm, make two (three) openings on the respective surfaces of solid electrolyte film 6a (for the second sensor 1b, being oxygen ionic conductive solid electrolytic thin- membrane 6a and 6b) and 6c, mate.On the surface of window portion, form the Pt metal film that thickness is 0.01 μ m by spatter film forming method.So just formed superficial layer film 7a (with regard to the second sensor 1b, being superficial layer film 7a and 7b) and 7c.
The formation of glass seal layer 9:
Be formed with on the whole surface at the back side of substrate 2 of superficial layer film 7a (for being superficial layer film 7a and 7b for the second sensor 1b) thereon, two sides parts with long limit of substrate 2, with and on be formed with the lip-deep part melting welding borosilicate glass of the substrate 2 of superficial layer film 7a (for the second sensor 1b, being superficial layer film 7a and 7b) and 7c, but do not form melting welding on the surface of superficial layer film 7a (for the second sensor 1b, being superficial layer film 7a and 7b) and 7c thereon, form sealant 9 thus.So just made gas sensor 1 with structure as shown in Figure 1.
Example
By being that 30% mixed gas adds nitrogen dioxide and prepares every kind of gas 11 with multiple content of nitrogen dioxide of 0 to 1000ppm to the nitrogen of the oxygen with 21vol%, 79vol% and the relative humidity under the room temperature.Utilize gas 11, measure the sensor output of the first sensor 1a and the second sensor 1b.
Particularly, the first sensor 1a and the second sensor 1b are placed in the measuring vessel, probe all contacts with two electrodes.In addition, sensor is placed in the container, makes the upstream side of the part of the catalyst metals film 5a that wins in the face of measurement gas.
Use the Pt well heater 12 installed that the temperature of measure portion is elevated to 400 ℃ by on glass seal layer 9, curing.Apply the DC voltage of 10mV, and measure its electric current output.The result who uses first sensor 1a to be obtained is shown in Figure 3, and the result who uses the second sensor 1b to be obtained is shown in Figure 4.Each is exported from 0 to 100mA variation, and can obtain to be proportional to the linear good output of nitric oxide concentration.In addition, measure and not influenced by 21% oxygen concentration, and do not drift about (drifting) etc.So can carry out stable measurement.But, the standard deviation width of the dispersion of the output data of first sensor 1a is wide, is about 6.4, and the standard deviation of the dispersion of the output data of the second sensor 1b is stable, is about 1.5.
Claims (2)
1. gas sensor comprises:
The porous tabular sintered body that comprises the silicon nitride needle-shaped crystals;
Begin to be formed at the first catalyst metals film and second catalyst metals film that comprises second catalyst metals that comprises first catalyst metals on the described porous tabular sintered body from the introducing side of measurement gas, make described first catalyst metals film and the described second catalyst metals film be in not contacted each other state;
Be formed at the oxygen ionic conductive solid electrolytic thin-membrane on the respective surfaces of described first catalyst metals film and the described second catalyst metals film;
Be formed at each lip-deep superficial layer film that comprises described first catalyst metals of each ion conductive solid electrolyte film, be in described first catalyst metals film and the not contacted each other state of the described second catalyst metals film, thereby constitute first measure portion and the 3rd measure portion; And
The glass seal layer that comprises monox, it is formed at other surfaces of described porous tabular sintered body, described porous tabular sintered body and is formed with on it on side of surface outside the surface of described first catalyst metals film and the described second catalyst metals film and described first measure portion and described the 3rd measure portion.
2. gas sensor comprises:
The porous tabular sintered body that comprises the silicon nitride needle-shaped crystals;
Begin to be formed at lip-deep two the first catalyst metals film and second catalyst metals films that comprise second catalyst metals that include first catalyst metals of described tabular sintered body from the introducing side of measurement gas, make described first catalyst metals film and the described second catalyst metals film be in not contacted each other state;
Be formed at the oxygen ionic conductive solid electrolytic thin-membrane on the respective surfaces of described two first catalyst metals films and described one second catalyst metals film;
Be formed at each lip-deep superficial layer film that comprises described first catalyst metals of each ion conductive solid electrolyte film, be in described two first catalyst metals films and the not contacted each other state of the described second catalyst metals film, thereby constitute first measure portion, second measure portion and the 3rd measure portion; And
The glass seal layer that comprises monox, it is formed at other surfaces of described porous tabular sintered body, described porous tabular sintered body and is formed with on it on side of surface outside the surface of described first catalyst metals film and the described second catalyst metals film and described first measure portion, described second measure portion and described the 3rd measure portion
The output of described second measure portion is added in the output of described first measure portion, and deducts the output of described second measure portion from the output of described the 3rd measure portion.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP137587/05 | 2005-05-10 | ||
| JP2005137587 | 2005-05-10 | ||
| JP045274/06 | 2006-02-22 |
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| CN1862255A true CN1862255A (en) | 2006-11-15 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103630595A (en) * | 2012-08-24 | 2014-03-12 | 特斯托股份公司 | Gas sensor |
| CN105334291A (en) * | 2014-08-05 | 2016-02-17 | 罗伯特·博世有限公司 | Micromechanical gas sensor device and manufacturing method thereof |
-
2006
- 2006-05-10 CN CN 200610081718 patent/CN1862255A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103630595A (en) * | 2012-08-24 | 2014-03-12 | 特斯托股份公司 | Gas sensor |
| CN103630595B (en) * | 2012-08-24 | 2017-11-17 | 特斯托股份公司 | Gas sensor |
| CN105334291A (en) * | 2014-08-05 | 2016-02-17 | 罗伯特·博世有限公司 | Micromechanical gas sensor device and manufacturing method thereof |
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