CN1278064A - Gas sensor contg. ceramic solid electrolytes, and method for making same - Google Patents

Abstract

The invention provides a ceramic laminate consisting of a substrate made of insulating ceramic and a solid electrolyte layer, suppresses the generation of a crack, and is firmly joined, and to provide an oxygen sensor element using the ceramic laminate. A ceramic laminate consisting of an alumina substrate 1 and a solid electrolyte layer 6 being jointed to the alumina substrate is obtained. The solid electrolyte layer is made of zirconia containing alumina of 10 to 80 wt.%, especially, 30 to 50 wt.%. Also, other ceramics layers, especially, a ceramics layer 7 made of the alumina, may be joined to the solid electrolyte layer. The relative density of the ceramics layer is 60 to 99.5%, preferably, 80 to 99.5%.

Description

Gas sensor contains solid electrolyte and its manufacture method of pottery

A kind of electrolyte of relate generally to of the present invention is particularly used in battery, transmits the electrolyte body or the layer of oxonium ion, lithium ion, sodion etc. between the electrode of battery.Specifically, the invention provides a kind ofly with solid electrolyte, measure specific gas, as O ₂, CO ₂, NO _x, HC, H ₂O and H ₂Deng the gas sensor of concentration.More particularly, the invention provides a kind of gas sensor that has electrochemical cell, with the method for making this gas sensor, described battery oxygen ionic conductive solid electrolyte, described electrolyte can transmit or conduct oxygen, thereby is determined at the specific gas component in the waste gas that internal combustion engine discharges.In addition, the invention provides the powerful gas sensor configuration of a kind of novel oxygen ionic conductive solid electrolyte and this material of use.

Usually, once propose to be used for a kind of solid electrolyte of use such as the zirconic multiple gases sensor of internal combustion engine control.For example, for the oxygen in the waste gas of measuring internal combustion engine, be extensive use of a kind of so-called exhaust gas oxygensensor, it utilizes the solid electrolyte of cylindrical and base seal.In addition, also proposed a kind of so-called thick film gas sensor, it utilizes the thick dielectric film that is formed on ceramic substrate or the rod to make measuring element, compares with exhaust gas oxygensensor, and this sensor energizing gas is fast measured process.This be because, compare with exhaust gas oxygensensor, its heat propagation efficient is higher.The thick film gas sensor can comprise a kind of insulating ceramics substrate or rod, wherein, is bumped into a heater wire that insulate with dielectric film, and described substrate and dielectric film co-sintering form the ceramic laminar structure as an one of gas sensor.

In the conventional method of making the thick film gas sensor, overlapping on unsintered alumina substrate, comprising the unsintered oxygen ionic conductive solid dielectric substrate of zirconia particles and unsintered metal electrode lines, this layer and substrate co-sintered form the layer structure of combination then.But the problem of this method is, because alumina substrate is different with thermal expansion with zirconic hot coefficient, and zirconia carries out phase transformation along with sintering temperature changes, generation volume change and/or thermal stress in lamina.This causes, the difficulty in obtaining zirconic high-quality oxygen ionic conductive solid dielectric substrate, and described dielectric substrate should pass through co-sintered, firmly is combined on the alumina substrate and does not lose the performance of requirement.In addition, in the final oxygen ionic conductive solid electrolyte layers that on layer structure, forms, under thermal cycle environment (thermal cycle hereinafter referred to as), in-20 to 1100 ℃, crack.

The crackle that is suppressed in the layer structure is disclosed in Japanese Patent Application Publication No.61-51557,61-172054 and 61-30073 and in the technology of last strong bonded oxygen ionic conductive solid electrolyte layers.Yet these still can not produce, but tape insulation ceramic substrate or rod, can be used as the thick film layers of eudiometry element, good solid electrolyte ceramic.

Therefore, the objective of the invention is to address the above problem, and a kind of new improved electrolyte body or layer are provided, it can fully be suppressed in manufacturing and/or the use, is included in the environment of high temperature gas and uses, the crackle of generation.

Another object of the present invention provides, and a kind of gas sensor that is used for is by the high tenacity layer structure of electrolyte ceramics layer and ceramic basic comprising.

Another object of the present invention provides a kind of method of making solid electrolytic body, layer and/or layer structure, and described solid electrolytic body, layer and/or layer structure can stand environment of high temperature gas and good performance is arranged in environment of high temperature gas.

Comprising the zirconic of a part or whole part stabilization, the real mark application facet of zirconic solid electrolyte it has been generally acknowledged that, mixes insulating ceramic materials in solid electrolyte material, by mass should be less than about 5% (=repetition number percent).In addition, the electrochemical action of the solid electrolyte of such aluminium oxide impurity reduction sintering.

But, the inventor finds, even solid electrolyte ceramic comprises the ceramic crystalline grain of the insulation of remarkable increase, as weight tens percent (promptly, weight 10-80%), wherein have a large amount of like this insulation crystal grain, the solid electrolyte of sintering still can sufficiently play the solid electrolyte of gas sensor battery, and can with contain weight and compare less than the normal ground solid electrolyte of 10% aluminium oxide.Especially according to the present invention, with containing tens percent high-purity alpha-alumina crystal grain, when the Zirconia electrolytic of a part or whole part stabilization formed a kind of layer structure, this layer structure also was better than containing the layer structure of the routine of small amounts aluminium in some physical property.

Specifically be that according to the present invention, when the mean grain size of the aluminium oxide, zirconia and the yttrium oxide powder that contain was less than 1 μ m in unsintered body or layer, behind the sintering, except insulation crystal grain, the electrolytical mean grain size of oxygen ionic conductive solid became and is not more than 2.5 μ m.

These find for a kind of being used in the high-temperature gas sensors of exploitation, good solid electrolyte body/and thick film layer structure (being at least one dielectric substrate and another material layer) be very useful.In general, the whole thickness of such layer structure on electrolyte part is 10-150 μ m, and described electrolyte partly is by co-sintered, combination on the thick high strength insulating substrate of aluminium oxide or the rod.In high purity aluminium oxide crystal grain is incorporated into electrolyte part with metal electrode such as platinum bonding, when forming the layer structure of gas sensor, the most handy alumina substrate.

First aspect according to the first embodiment of the present invention, a kind of solid electrolyte ceramic body is provided, the electrolyte ceramics that contains insulating ceramics crystal grain and part or all of stabilization, wherein ceramic body contains the insulating ceramics crystal grain of weight 10-80%, and the mean grain size in the electrolyte ceramics of the part or all of stabilization that they are distributed in is not more than 1 μ m.Remainder in the insulator, promptly ceramic body weight is the electrolyte of part or all of stabilization more than 20%.At this, when electrolyte is used for the battery of gas sensor, form electrolyte body, it is important that the zirconia crystal grain of stabilization is connected each other continuously with the state that surrounds insulation crystal grain.Otherwise the ion with battery of electrode can not shift to another from an electrode.If form the mean grain size of insulating ceramics crystal grain, then can lose the machinery and the electric property of electrolyte body.

In the second aspect of first embodiment, importantly, the solid electrolyte ceramic body has the insulating ceramics crystal grain that is higher than 99% average purity.When the center of crystal grain was measured, the better purity of insulating ceramics crystal grain was greater than 99.9%, preferably greater than 99.99% or 99.995%, because highly purified crystal grain can not combine with other stupalith.Though for highly purified insulation crystal grain various selections are arranged, when requiring solid electrolyte ceramic to see through its transmission oxonium ion, the alumina grain with above-mentioned purity is best.Reason is that aluminium oxide (aluminium oxide 2O3) itself has oxygen.

High high purity aluminium oxide is mixed in mainly be made of unsintered body or layer in addition electrolyte ceramicses such as zirconia and hafnium oxides than 99.9%, in forming the good oxygen ionic conductive solid electrolyte ceramics of the present invention, use inorganic stabilizers and some organic binder bonds such as yttria and magnesium oxide.The purity, particularly alumina grain of insulation crystal grain are for preventing that in use the electricity or the reduction of mechanicalness burning of solid electrolyte (sintering) are important.The purity of the alumina powder of mixing in unsintered dielectric substrate is greater than 99.99% o'clock, or more preferably greater than 99.995% o'clock, can obtain good many performances of solid electrolyte.

Another key factor is the zirconia powder of mixing and the purity of yttria.The weight of the external contaminant except zirconia and yttria should be less than 1%, is not more than 0.1 better, is not more than 0.05% best.

In the third aspect of first embodiment, the solid electrolyte ceramic body has the electrolyte of a part or whole part stabilization, and it contains the zirconia of a part or whole part stabilization of weight 20%-90%, and zirconia purity is greater than 99%, and is better greater than 99.9%.The electrolyte of a part or whole part stabilization that contains at ceramic body, when having mean grain size and being not more than the form of solid fine grain of 2.5 μ m, the machinery or the electrical property of solid electrolyte ceramic body or layer are strengthened, particularly when having alumina grain.

Specifically be, with the zirconia that is formed on a part or whole part stabilization in the ceramic body together, the weight of the insulating ceramics crystal grain that contains is in the scope below 80% time, the resistivity of oxide ion conduction ceramic body or layer becomes less than 10 Ω m.More specifically, cardinal principle is significantly less than 5 Ω m by the resistivity of the electrolyte ceramics of zirconia (zirconia of the yttria-partially stabilizedization) formation of the alumina grain of 30-70% and partially stabilizedization that remains 30-70%, measure in equal state, this can with in electrolyte, contain substantially, except that zirconia and yttrium, the performance of the conventional known solid electrolyte ceramic body of the not purifying insulating ceramics less than 20% is compared.

The electrolyte ceramics that pollutes at purifying not or band, when being contained in the zirconic electrolyte body of a part or whole part stabilization as aluminium oxide less than 99%-purity, mix people's weight at so not purifying pottery, only be increased at 20% o'clock from 10, depress 800 ℃ of temperature surveys in room atmosphere, resistivity significantly increases greater than-1000 Ω m from 20 Ω m approximately.Its reason is, pollutant in the aluminium oxide and aluminium oxide block and hinder oxonium ion etc. in other words and pass the Zirconia electrolytic that forms in vivo.

On the other hand, below more specifically the explanation root a tree name principle of the present invention, when using a kind of high-purity alpha-alumina and a kind of high-purity mangesium oxide zirconium and a kind of high purity yttria, when mixing weight less than 10% high-purity alpha-alumina, the resistivity of root a tree name electrolyte body of the present invention is less than 0.1 Ω m, and when mixing the same aluminium oxide of weight 10-50%, resistivity is approximately less than 5 Ω m.It is shocking, according to the present invention, be the identical high-purity alpha-alumina of 30-70 high-load owing to add weight to electrolyte body, and resistivity value is, less than 20 or 40 Ω m, the low value of several Ω m only arranged.In this article, be under the temperature of 800 ℃ of ambient atmospheres, with two electrodes, on the electrolyte ceramics body, according to the resistivity of known Cole-Cole plotting curves method measurement.

As mentioned above, in solid electrolyte, add the high-purity mangesium oxide aluminium grain and do not reduce its electric property that use needs as gas sensor.In addition, by changing the percentage that aluminium oxide mixes, make with layers such as other body or metal level, insulating ceramics substrate or layer and even metal level be complementary, so also can advantageously change other physical values of thermal expansivity and physical strength etc.

A plurality of solid electrolyte bodies and/or layer are constituted rhythmo structure, and each has the different percentage of high-purity insulation crystal grain, and the very big advantage that exists is because each electrolyte body or layer obtain different physical property (electricity, chemistry and mechanical property).Each electrolyte body or layer can have the metal electrode that forms electrochemical cell, can have the ceramic electrode that comprises some metals and pottery, or also can have the insulator that bonds with it.

The present invention may be used on the various electrolytical batteries of using, as lithium or sodion conduction battery with comprise polymkeric substance or the electrolytical ion separator of solid ceramic, as long as just the high-purity insulating ceramics crystal grain that mixes does not cause in these batteries or separation vessel that serious problems can.Devices such as battery as herein described or separation vessel meanings be that specific ion only from wherein passing through, and does not allow other ion to pass through as oxygen and lithium.

First aspect according to a second embodiment of the present invention, a kind of gas sensor is provided, it has an electrochemical cell of measuring gas concentration, it comprises an oxygen ionic conductive solid dielectric substrate and is formed on metal electrode on the oxygen ionic conductive solid dielectric substrate that wherein the oxygen ionic conductive solid dielectric substrate contains the insulating ceramics crystal grain of weight 10-80%.

The above-mentioned gas sensor preferably also comprises: an alumina substrate, on described substrate, form the oxygen ionic conductive solid dielectric substrate in combination, and a well heater is positioned at alumina substrate; An oxygen reference electrode forms on the oxygen ionic conductive solid dielectric substrate in combination; With a gasmetry electrode, on the oxygen ionic conductive solid dielectric substrate, form in combination, wherein the oxygen ionic conductive solid dielectric substrate contains zirconia and alumina grain, make that the weight of the alumina grain that contains at the oxygen ionic conductive solid dielectric substrate is the 10-80% of oxygen ionic conductive solid dielectric substrate general assembly (TW), preferably 20-75%.In this sensor, when the content of its alumina grain is the 30-70% of oxygen ionic conductive solid dielectric substrate general assembly (TW), can satisfies and can improve sensor temperature and make its vibration, internal combustion engine uses, great majority are the gas sensor of base with the oxonium ion, as lambda sensor, NO _xThe requirement of sensor and HC sensor.

In addition, gas sensor also can comprise: a middle layer, between alumina substrate and oxygen ionic conductive solid dielectric substrate, wherein zirconia and insulating ceramics are contained in the middle layer, make insulating ceramics content and oxygen ionic conductive solid dielectric substrate different in middle layer.In this structure, obtain the premium properties of pyrostat.The insulating ceramics that the weight content ratio oxygen ionic conductive solid dielectric substrate of the insulating ceramics that contains in the middle layer contains is high at least 10% o'clock, is expected further to improve performance.The best main material that contains in the insulating ceramics substrate is a high-purity alpha-alumina.

Can on gasmetry electrode and/or oxygen ionic conductive solid dielectric substrate, form another ceramic layer of the relative density with 60-90%.On this ceramic layer of described density, on the outside surface of ceramic layer, can form a gas defence layer, as spinel layer, prevent that the electrode of measurement gas is poisoned by extraneous element, as lead.

Importantly, the insulation crystal grain that contains in the oxygen ionic conductive solid dielectric substrate in the said structure of gas sensor is that purity is higher than 99.9%, or is higher than the product that 99.99% aluminium oxide forms.

Second aspect according to second embodiment, the gas sensor that provides has the electrochemical cell of measurement gas, it comprises: insulating ceramics substrate and the oxygen ionic conductive solid dielectric substrate by sintering combination on substrate, wherein the oxygen ionic conductive solid dielectric substrate contains zirconia and insulating ceramics, make that the total amount at zirconia and insulating ceramics is at 100% o'clock, insulating ceramics weight is 10%-80%.This insulating ceramics substrate is that shape is for example cylindric or excellent aluminium oxide, forms the oxygen ionic conductive solid dielectric substrate thereon in combination; A well heater is in cylindric or excellent aluminium oxide; An oxygen reference electrode, combination forms on the oxygen ionic conductive solid dielectric substrate; Electrode with a gasmetry, on the oxygen ionic conductive solid dielectric substrate, form in combination, wherein the oxygen ionic conductive solid dielectric substrate contains zirconia and alumina grain, makes that the alumina grain that contains at the oxygen ionic conductive solid dielectric substrate is the 10-80% of oxygen ionic conductive solid dielectric substrate general assembly (TW).

Can be with " substrate " of any insulating ceramic materials (or rod), but it should be stablized at high temperature, and insulativity is arranged.When " electrolyte ceramics " was the lazy condition of oxide ion conduction, the good example of such insulating ceramic materials was aluminium oxide, mullite and spinel, though be not to be defined in these especially.Alumina substrate is best among them, because, when forming a stratiform structure of gas sensor element, can co-sintered heat electrolytical single line in all other parts co-sintered (sintering simultaneously), make to be set in the alumina substrate.

This oxygen ionic conductive solid dielectric substrate contains " electrolyte ceramics " and " insulating ceramics ", and wherein according to this aspect of the invention, the weight of insulating ceramics accounts for 10-80%.Form the oxygen ionic conductive solid dielectric substrate in combination on insulating substrate, make to form a kind of solid layer structure, it can firmly maintain in the outer cover of the gas sensor of routine, and gas sensor is often to be in the environment of harsh vibration.

Because oxygen ionic conductive solid dielectric substrate of the present invention contains insulating ceramics as one of key component, be bonded to one when forming the ceramic laminar structure by co-sintered at dielectric substrate and ceramic substrate, the thermal stress that the difference of thermal expansivity increases between substrate and oxygen ionic conductive solid dielectric substrate, greatly alleviated, thereby enough suppressed crackle or lamination in the layer structure.

By utilizing insulating ceramics in the above range, be suppressed at the growth of the zirconia grain size in the oxygen ionic conductive solid dielectric substrate effectively, thereby suppress zirconic phase transformation, otherwise, it is to take place owing to the temperature variation that stands in sintering or thermal cycle.Even phase transformation has taken place in part, because the easy dispersion of stress can suppress crackle.

As mentioned above, the oxygen ionic conductive solid dielectric substrate contains the insulating ceramics that weight is 10-80%.Weight content at insulating ceramics is lower than at 10% o'clock, can not fully be suppressed at the crackle in the oxygen ionic conductive solid dielectric substrate, may cause the oxygen ionic conductive solid dielectric substrate to separate from insulating substrate, particularly in limit portion.The weight content of insulating ceramics was greater than 80% o'clock in the oxygen ionic conductive solid dielectric substrate that has insulating substrate to use together, and the oxygen ionic conductive solid dielectric substrate is reduced to out of use scope.For the layer structure of gas sensor element, the insulating ceramics weight content is better at 20-75%, 30-70% is better.

Insulating ceramics in the oxygen ionic conductive solid dielectric substrate or zirconia content not only can be obtained by the conventional chemical analysis, and can be obtained by the image analysis that electron microscopic videotapes.For example, the BEI image (back scattered electron image) that utilizes a scanner scans to take by a kind of SEM (scanning electron microscope) obtains visual electronic information.According to this electronic information, use an image analyzer (as the LUZEX FS image analyzer of NIRECO production) to determine to be contained in insulating ceramics crystal grain and the intercrystalline area ratio of zirconia in the dielectric substrate.According to the area ratio of such acquisition, by approximate treatment theoretical volume ratio, and the volume ratio that will obtain like this converts the weight content of insulating ceramics to.

The zirconia that contains in the oxygen ionic conductive solid dielectric substrate preferably is the stabilizing zirconia shape, or the PSZ shape.If it is best to require to be formed on the physical strength of the on-chip oxygen ionic conductive solid dielectric substrate of insulating ceramics, tough domestic animal and thermal shock strength, be 2-9% preferably with mol ratio, preferably the zirconia of partially stabilizedization of yttria of 4-8% mixes with the high-purity alpha-alumina insulating ceramics, forms best dielectric substrate of the present invention.Other stabilizing agent can be magnesium oxide and calcium oxide.

According to the third aspect of the second embodiment example, gas sensor can also be included in a middle layer between insulating substrate and oxygen ionic conductive solid dielectric substrate, and zirconia and insulating ceramics are contained in the middle layer.The more suitable weight of the insulating ceramics that contains in the middle layer is at least than oxygen ionic conductive solid dielectric substrate big by 10% (preferably 15%).By utilizing such middle layer, substrate and oxygen ionic conductive solid dielectric substrate with electrode of using as battery can bond each other more firmly by co-sintered.Also available a plurality of middle layers.By form at least one electrode on the middle layer, the middle layer also can partially or entirely be used as battery, because electrolyte ceramics is also contained except insulating ceramics in the middle layer.Preferably, such aluminium oxide and zirconia can be contained in the middle layer that directly contacts insulating ceramics substrate (or rod), make that aluminium oxide and zirconic amount are higher than in the middle of the middle layer being.Can contain such aluminium oxide and zirconia with the middle layer that the oxygen ionic conductive solid dielectric substrate directly contacts, make that the amount of zirconia and aluminium oxide is higher than being in the middle of the middle layer.In these structures of the present invention, reduced the stress that produces by the temperature variation between phase transformation and outermost layer and substrate in a large number.

According to the fourth aspect of second embodiment, the insulating ceramics that contains in substrate, oxygen ionic conductive solid dielectric substrate or middle layer is aluminium oxide preferably.This is because stablize in high temperature alumina; Aluminium oxide has good physical strength, thermotolerance and insulativity; With with produce good binding intensity during oxygen ionic conductive solid dielectric substrate co-sintered combines.

The 5th aspect according to second embodiment can form at least two electrode layers on the oxygen ionic conductive solid dielectric substrate, thereby gas sensor element for example is used as the monolithic gas sensor element.In the same side of oxygen ionic conductive solid dielectric substrate, or can form pair of electrode layers at each opposition side of oxygen ionic conductive solid dielectric substrate.

According to the 6th aspect of second embodiment, on the oxygen ionic conductive solid dielectric substrate of outermost, form ceramic layer with 60-90% relative density.The 7th aspect according to second embodiment, on oxygen ionic conductive solid dielectric substrate and electrode, or between dielectric substrate and middle layer, can form the ceramic layer of 60-99.5% relative density, thereby further suppress to prevent the crackle in the gas sensor element (comprising the oxygen ionic conductive solid dielectric substrate).

According to the first aspect of third embodiment of the invention, the method for making a kind of gas sensor is provided, comprise step: form aluminium oxide, zirconia and yttrium oxide powder potpourri; On the not sinter layer that potpourri forms, place two non sintered metal electrodes; With with described layer, two not sintered electrode and insulating substrate simultaneously at 1350-1600 ℃ of sintering, formation has a kind of ceramic laminar structure of the oxide ion conduction battery of oxygen ionic conductive solid dielectric substrate, described oxygen ionic conductive solid dielectric substrate transferable oxonium ion between the electrode of sintering, wherein the oxygen ionic conductive solid dielectric substrate contain the alumina grain of weight 10-80% and 20-90% by the part or all of stable zirconia of yttria.

In said method, the zirconia of formation mixture of powders and yttria preferably obtain by co-precipitation in a kind of liquid, and described liquid contains the alkoxide of zirconia and yttria, because can obtain the powder that homogeneous mixes by co-precipitation.Producing free of contamination potpourri, as be lower than 0.1% the zirconia and the potpourri of stabilizing agent with the pollution of usefulness in the methods of the invention, is important.That is, the powder of zirconia and yttria is free of contamination being higher than 99.9% purity level.

The purity of the alumina grain that mixes with the potpourri of zirconia and stabilizing agent is prior.The purity of alumina powder is more than 99.9% in the method for the invention, or better more than 99.99%, because a high-purity alpha-alumina crystal grain tends to not form solute with zirconia or yttria when sintering like this, and it is too high not cause that electrolytical internal resistance is risen for gas sensor.

Second aspect according to third embodiment of the invention, provide and made a kind of gas sensor (promptly, the method of layer structure gas sensor element), comprise step: (1) forms non-sintered ceramic layer, it contains such Zirconium oxide powder and insulating ceramics powder, and the total amount that makes insulating ceramics grain weight amount and zirconia in sinter layer not and insulating ceramics powder is than being 10-80%; (2) overlapping non-sintered ceramic layer on dielectric ceramic layer forms a kind of non-sintered ceramic stratiform structure; (3) the described non-sintered ceramic stratiform of sintering structure in combination, at final sintering the outmost surface of ceramic laminar structure on form sintering the oxygen ionic conductive solid dielectric substrate so that sintering the grain size of solid electrolyte less than 2.5 μ m.

For the method for above-mentioned second aspect, it is very desirable using the thin Zirconium oxide powder less than the mean grain size of 1 μ m that obtains by precipitation, so that the solid electrolyte grain size that has obtained less than the sintering of 2.5 μ m.Preferably use contain from yttria, magnesium oxide with/become the thin Zirconium oxide powder of the stabilizing agent of selecting the calcium oxide, the Zirconium oxide powder that contains stabilizing agent is made by above-mentioned co-precipitation.

The connotation of term " sintering in combination " or " co-sintered " is to carry out such step: will be at least one deck sintering oxygen ionic conductive solid dielectric substrate or body weight are not stacked in another not on the substrate or body of sinter layer, pottery or metal; Sinter a single unit into the layer structure that will cause.Insulating ceramics for example comprises: aluminium oxide, mullite and spinel, but be not limited to these especially.For high-temperature stability, mechanical property, thermotolerance and insulativity, aluminium oxide is best insulating ceramic materials.

According to the third aspect of the 3rd embodiment, " sintering " carries out better (being preferably in 1400-1550 ℃) at 1350-1600 ℃.When sintering temperature is lower than 1350 ℃, sintering the layer structure abundant sintering of failing; That is, almost can not obtain the layer structure of even sintering.When sintering temperature was higher than 1650 ℃, the grain growth that forms in dielectric substrate was unusual.At said temperature scope sintering, continue 0.5-6 hour better (preferably 1-2 hour).

According to the fourth aspect of the 3rd embodiment, preferably use the powder that roughly constitutes by zirconia and stabilizing agent, described powder is to obtain by coprecipitation, and contains zirconia and stabilizing agent.Evenly mix by coprecipitation zirconia and stabilizing agent, and the zirconia material powder has little grain size; Specifically be to obtain being not more than the mean grain size of 1.0 μ m easily.Such stabilizing agent for example has yttria, magnesium oxide and calcium oxide.

On the corresponding two opposite sides of oxygen ionic conductive solid dielectric substrate, can form " potential electrode " and " oxygen reference electrode "; For example, by the cream that uses platiniferous print electrode model, sintering subsequently.The zirconia of aluminium oxide and/or part or whole stabilization can be added on the platiniferous cream.Oxygen reference electrode and potential electrode can be formed on the respective opposite both sides of oxygen ionic conductive solid dielectric substrate.Gas under measuring contacts with potential electrode, the oxygen of oxygen concentration reference gas contact simultaneously reference electrode.As a result, according to difference in oxygen concentration between, between electrode, by producing electromotive force based on the oxygen concentration cell effect that can take charge of special formula.

" well heater " in substrate can heat the oxygen ionic conductive solid dielectric substrate, and comprises the heater head of a heating part and heating part.Heater head connects heating part and lead, so that trsanscondutor adds a curtage, the heating heating part.In having the gas sensor element of well heater, the hot occurrence features of well heater is determined that by the resistance of heater material it preferably can or change sintering temperature by control and extensively regulate.Gas sensor element according to the inventive method is made allows 1350-1600 ℃ wide burning part temperature in the mill.Promptly, during at heater section, unsintered substrate with in unsintered oxygen ionic conductive solid dielectric substrate co-sintered, owing to use the solid electrolyte of salic crystal grain of the present invention, advantageously, the resistance of well heater can be controlled in positive and negative approximately 50% wide region of desired value.

According to the 5th aspect of the 3rd embodiment, the gas sensor that provides comprises: an insulating ceramics substrate and the oxygen ionic conductive solid dielectric substrate that combination forms on substrate; A well heater is positioned at the insulating ceramics substrate; An oxygen reference electrode is formed on a side of oxygen ionic conductive solid dielectric substrate; With a potential electrode, measure gas, be formed on the opposite side of oxygen ionic conductive solid dielectric substrate, wherein the oxygen ionic conductive solid dielectric substrate comprises such zirconia and insulating ceramics, weight total amount at zirconia and insulating ceramics is 100% o'clock, and insulating ceramics weight is 10-80%.

This " substrate ", " oxygen ionic conductive solid dielectric substrate " and " zirconia " content in the oxygen ionic conductive solid dielectric substrate of sintering and " insulating ceramics " content can be to aforesaid others similar so that produce similar effect.The alumina grain weight that can contain in the oxygen ionic conductive solid dielectric substrate is that 20-75% is better, is preferably 30-75%.

Gas sensor element also can be included between substrate and oxygen ionic conductive solid dielectric substrate and/or the middle layer between substrate and oxygen reference electrode, and the middle layer contains the zirconia and the insulating ceramics of part and monolithic stabilityization.The middle layer contains such zirconia and insulating ceramics, is 100% o'clock in the gross weight of zirconia and insulating ceramics, and the insulating ceramics weight content in middle layer is at least than high 10% in the oxygen ionic conductive solid dielectric substrate better (being preferably 15%).By this way, the middle layer can have a thermal expansivity between substrate and oxygen ionic conductive solid dielectric substrate, thereby suppresses the crackle in the oxygen ionic conductive solid dielectric substrate more reliably.And, because the insulating ceramics content in middle layer is between the content of the content of the substrate that insulating ceramics forms and oxygen ionic conductive solid dielectric substrate, it is 10% to 80% insulating ceramics that the oxygen ionic conductive solid dielectric substrate contains weight, substrate and oxygen ionic conductive solid dielectric substrate pass through more secure bond of middle layer, have less stress, prevent that layering and crackle from taking place.

Particularly, at the content of the insulating ceramics of oxygen ionic conductive solid dielectric substrate and the ratio of insulating substrate, when much lower, can be with two or multilayer middle layer.At this moment, the insulating ceramics content in middle layer can reduce in proper order, make the middle layer that contacts with substrate (as an alumina substrate) have the highest insulating ceramics content, and the middle layer that contacts with the oxygen ionic conductive solid dielectric substrate has minimum insulating ceramics content, thereby suppresses the crackle in the oxygen ionic conductive solid dielectric substrate more effectively.In addition, substrate and oxygen ionic conductive solid dielectric substrate can bond more securely by two or more middle layers of different insulative ceramic content.Also forming the middle layer makes and extends on the whole surface of substrate.In addition, except the moulding of reference gas idiomorphism, in the situation of the gas sensor of reference gas introducing type, can form the middle layer or all the two or more middle layers that contact with the oxygen ionic conductive solid dielectric substrate, make it have reference gas and introduce passage.

Intermediate layer thickness (when comprising two or more middle layer, referring to the whole thickness in each middle layer) is better for 5-200 μ m, for 20-50 μ m best.During less than 5 μ m, the middle layer can not fully play a part to suppress crackle in the oxygen ionic conductive solid dielectric substrate, causes that substrate and oxygen ionic conductive solid dielectric substrate can not secure bond at intermediate layer thickness.Situation at gas sensor element, when middle layer thickness surpasses 200 μ m, well heater in the insulating ceramics substrate postpones to the heat transfer of oxygen ionic conductive solid dielectric substrate, can not the oxygen ionic conductive solid dielectric substrate be worked by effective heating.In addition, blocked up middle layer can be because thermal strain causes crackle in the oxygen ionic conductive solid dielectric substrate.

According to the 6th aspect of the 3rd embodiment, be contained in the insulating ceramics aluminium oxide preferably in substrate and the oxygen ionic conductive solid dielectric substrate.This is stable because of aluminium oxide at high temperature, has good physical strength, thermotolerance and insulativity, and with the bonding of oxygen ionic conductive solid dielectric substrate in produce superior bond strengths rendering.

According to the 7th aspect of the 3rd embodiment, the ceramic layer with 60-99.5% (preferably 80-99.5%) relative density can be bonded on the potential electrode of substrate opposite side, thereby suppresses the crackle in the oxygen ionic conductive solid dielectric substrate effectively.。When ceramic layer has less than 60% phase specific density, prevent the layer of poisoning even be provided with, can not prevent effectively that also potential electrode poisoned by Pb, Si or P.Surpass 99.5% in the phase specific density, the oxygen that contains in the gas when measuring can not fully reach potential electrode fast, and the result can influence the sensitivity of gas sensor element.

The thickness of ceramic layer is 10-200 μ m, for 20-100 μ m is better, is preferably 25-70 μ m.At the thickness of ceramic layer during less than 10 μ m, the ceramic layer potential electrode that can not adequately protect, and can not fully integrally reinforce gas sensor.

The preventing of guard electrode poisoned layer can be by the spinel manufacturing.To form when preventing to poison layer, with the part of the layer corresponding ceramic layer that prevent to poison can be by applying a kind of thin pulp formation, making becomes a relative thin layer.The remainder of ceramic layer can form by having substantially the thin layer that equates with the thickness of the layer that prevents to poison, and making becomes a relative thick-layer.Therefore, the gas sensor element of making does not comprise any step part that can cause that stress is concentrated.

In gas sensor element (the can be described as the ICP type) situation that takes place certainly with reference to oxygen, the thickness of oxygen ionic conductive solid dielectric substrate is 10-70 μ m better (20-60 μ m is better, preferably 30-50).During less than 10 μ m, the life-span of oxygen ionic conductive solid dielectric substrate can be not enough at thickness.In order to form a thick oxygen ionic conductive solid dielectric substrate, can repeat repeatedly with the cream printing.

In the gas sensor element situation of introducing the reference gas build, the thickness of oxygen ionic conductive solid dielectric substrate is 0.5-2 μ m better (0.7-1.5 μ m is better, is preferably 0.9-1.3 μ m).Thickness is less than 0.5 μ m, and the oxygen ionic conductive solid dielectric substrate can not have sufficient mechanical strength.Thickness is greater than 2 μ m, and the thermal capacitance of gas sensor element increases, and may influence the sensitivity of low temperature.

Feature of the present invention is that zirconic mean grain size is not more than " 2.5 μ m ", and " mean grain size " is according to scanning electron microscope (hereinafter claiming SEM), obtains 5000 times of solid layer surface picture of taking down.Take retroeflection electron image (hereinafter claiming BEI) by SEM, can take the crystal grain of different components with different colours or density.The maximum gauge of each crystal grain in the SEM photo is taken as grain size, and the particle mean size that is contained in all the zirconia crystal grain in square of the unit of 5cm * 5cm in the photo is called first mean grain size.From same solid electrolyte layer, obtain five first mean grain sizes respectively corresponding to five SEM photos of five different visual fields, and average then, obtain second mean grain size.This second mean grain size is as " mean grain size " that define among the present invention.

Can see from the following autoclave test result that partly illustrates at example, during greater than 2.5 μ m, solid electrolyte layer does not have enough life-spans in zirconic mean grain size.By keeping the zirconia mean grain size that is not more than 2.5 μ m, press down growing up of sharp zirconia crystal grain in solid electrolyte layer effectively, thereby suppress zirconic phase transformation, otherwise the temperature variation of working as in sintering step or thermal cycle can cause phase transformation.Even part undergoes phase transition, also because the easy dispersion of stress can suppress crackle.It is better that zirconic mean grain size is controlled at 0.1-2.3 μ m, preferably at 0.3-2.0 μ m.By reaching the mean grain size of such scope, can suppress the crackle of solid electrolyte layer.

It is desirable (0.5-4.2 μ m is better, and 0.5-3.5 μ m is best) that the zirconic above-mentioned grain size that contains in solid electrolyte layer is distributed in 0.5-5 μ m.Even mean grain size is not more than 2.5 μ m, mixes the crystal grain that has above the maximum grain size of 5 μ m and also can cause crackle.

In order to suppress crackle, the 50-100% (60-100% is better, and 70-100% is best) in five visual fields observing on each SEM photo in the zirconia grain size of each corresponding unit in square should have the maximum grain size that is not more than 3 μ m.

In order to suppress crackle, preferably, zirconic mean grain size is not more than 2.5 μ m, zirconic crystal grain has the largest grain size that is not more than 5 μ m, and the 50-100% in the zirconia grain size of each corresponding unit in square should have the maximum grain size that is not more than 3 μ m in five visual fields observing on each SEM photo.

The zirconia crystal grain that contains in solid electrolyte layer comprises those that be cubic crystalline phase (hereinafter claiming " T phase "), is single Dou crystalline phase those (hereinafter claiming " M phase ") and is cube crystalline phase those (hereinafter titles " C mutually ").The mean grain size that is the crystal grain of T phase is not more than 2.5 μ m (0.1-2.3 μ m is better, is preferably 0.3-2.0 μ m).T tends to be phase-changed into the M phase mutually under 200 ℃ of environment temperatures.Humidity is quickened this phase transformation, and this phase transformation relates to stereomutation.Therefore,, suppress zirconic phase transformation by obtaining the mean grain size that is not more than 2.5 μ m for the crystal grain that is the T phase, otherwise, be to produce during the temperature variation of this phase transformation in standing sintering step or thermal cycle.The account form of mean grain size of crystal grain that is the T phase is similar to the mode of aforementioned calculation zirconia mean grain size.As mentioned above, utilize the BEI image, the crystal grain that is the T phase can be distinguished mutually with the crystal grain that is other phase.

Zirconia is with stabilization, or the zirconic form of steadyization of part to be contained in the solid electrolyte layer be desirable.Preferably, the zirconia that contains a large amount of steadyization of part.This makes zirconia be not easy to phase transformation, otherwise, be to produce during the temperature variation of this phase transformation in standing sintering step or thermal cycle.In addition, also improve each physical property of solid electrolyte layer, as physical strength, toughness and thermal-shock resistance.It should be noted that in mole, the zirconia content in solid electrolyte layer is taken as at 100% o'clock, the stabilizing agent that solid electrolyte layer contains 2-9% is preferably, is preferably 4-9%.The example of this class stabilizing agent comprises yttria, magnesium oxide and calcium oxide, and yttria is best.

As mentioned above, by in solid electrolyte layer, mixing insulating ceramics and zirconia, and obtain the zirconia mean grain size that is not more than 2.5 μ m, can suppress crackle.Root is drawn together second aspect present invention, and the mean grain size of the insulating ceramics that contains in solid electrolyte layer is not more than 1.0 μ m, thereby strengthens the effect that suppresses crackle.The mean grain size of insulating ceramics is that 0.05-0.8 μ m is better, is preferably 0.1-0.6 μ m.When the mean grain size of insulating ceramics reduced, zirconic mean grain size can further reduce.The account form of the mean grain size of insulating ceramics is similar to calculating zirconia mean grain size.

The insulating ceramics of solid electrolyte layer or zirconic content not only can be obtained by the conventional chemical analysis, and can obtain by the image analysis of electron microscopic according to elephant.For example, the BEI image, it is taken in the same manner as described above with SEM, utilizes scanner scans to obtain the electronic information of image.According to this electronic information, with image analysis (as, LUZEX FS, NIRECO product) obtain insulating ceramics crystal grain and the intercrystalline area ratio of zirconia.According to this area ratio, approximate treatment theoretical volume ratio converts this volume ratio to insulating ceramics content.

Ceramic laminar structure of the present invention can be used on, and comprises in the lambda sensor battery of solid electrolyte layer and the layering that is formed on the pair of electrodes on the solid electrolyte layer.In the layering lambda sensor element of routine, solid electrolyte layer is by the zirconia manufacturing, and substrate is to realize electrical isolation by insulating ceramics (as aluminium oxide) manufacturing.As a result, because the increase of the thermal stress between solid electrolyte layer and substrate, and the phase transformation that is associated with temperature variation in sintering and the thermal cycle, conventional layering lambda sensor element is easy to occur the crackle of solid electrolyte layer.By utilizing ceramic laminar structure of the present invention, can suppress the crack problem of lambda sensor element effectively.In the same side of solid electrolyte layer, or can form pair of electrode layers at each opposition side.

Reference electrode and potential electrode are formed on the corresponding two opposite sides of solid electrolyte layer.Gas contact measurement electrode during measurement, the reference electrode of reference gas contact simultaneously.As a result, based on difference in oxygen concentration between, between electrode, produce electromotive force by the oxygen concentration cell effect.

In the situation that the lambda sensor element (ICP type) with reference to the oxygen type takes place certainly, it is better that the thickness of solid electrolyte layer is not less than 10-70 μ m (20-60 μ m is better, and 30-50 is best).At thickness during less than 10 μ m, the life-span deficiency of solid electrolyte layer.In order to form thick solid electrolyte layer, must repeat repeatedly, thereby the work that influences is carried out with the cream printing.Therefore thickness is not more than 70 μ m and is advisable.

Fig. 1 is the perspective illustration of an embodiment of gas sensor, comprises the solid electrolyte layer (2) according to salic crystal grain of the present invention, and other parts that form the gas sensor layer structure are taken apart;

Fig. 2 is the photo of taking behind two solid electrolyte layers that carry out autoclave life test (sample 2) co-sintered bonding, wherein top layer is according to the present invention, a solid electrolyte layer of salic crystal grain, showing haunts cracks, bottom is a solid electrolyte layer that does not have alumina grain, and demonstrates and crack;

Fig. 3 is the photo of taking behind two solid electrolyte layers that carry out autoclave life test (sample 3) co-sintered bonding, wherein top layer is according to the present invention, contain a solid electrolyte layer with the alumina grain of sample 2 different sizes, do not illustrate and crack, bottom is a solid electrolyte layer that does not have alumina grain, and the crackle of generation is shown;

Fig. 4 is according to the present invention, and the electron microscopic image on the surface of a solid electrolyte layer (sample 1) of salic crystal grain amplifies 5000 times;

Fig. 5 is according to the present invention, and the electron microscopic image on the surface of a solid electrolyte layer (sample 2) of salic crystal grain amplifies 5000 times;

Fig. 6 is according to the present invention, and the electron microscopic image on the surface of a solid electrolyte layer (sample 3) of salic crystal grain amplifies 5000 times;

Fig. 7 is according to the present invention, and the electron microscopic image on the surface of a solid electrolyte layer (sample 5) of salic crystal grain amplifies 5000 times;

Fig. 8 is according to the present invention, and the electron microscopic image on the surface of a solid electrolyte layer (sample 8) of salic crystal grain amplifies 5000 times;

Fig. 9 is according to the present invention, and the electron microscopic image on the surface of a solid electrolyte layer (sample 14) of salic crystal grain amplifies 5000 times;

Figure 10 is the perspective illustration of another embodiment that has the gas sensor of solid electrolyte body of the present invention or layer (26), and other part that forms this another gas sensor layer structure is taken apart.

The example of making below by a gas sensor element describes the present invention in detail.But should not think that the present invention is defined in these examples.Example 1

Make from a gas sensor element that takes place with reference to the oxygen type.With reference to Fig. 1 this manufacturing course is described.Fig. 1 schematically illustrates gas sensor element in exploded view.

(1) makes one by being sintered into the unsintered alumina wafer of substrate

Add the butyral resin and the dibutyl ester phthalic acid salt of different scheduled volumes to alumina powder, thereby be prepared into cream as insulating ceramics.By scraper cream is formed thin slice, obtain when sintering it and become the unsintered alumina wafer (a) of substrate (1a) and it becomes the unsintered alumina wafer (b) of substrate (1b) when sintering, each plays not sintering substrate, and it is thick to have a 0.4mm.Substrate (1a) and (1b) constitute an alumina substrate (1).

(2) form the well heater pattern

Add salic platinum cream on the surface of sintering oxidation aluminum slice not, form well heater pattern (20 μ m thickness), it becomes heating part (3) and heater head partly (3a) and (3b), subsequent drying when sintering.On the sintering oxidation aluminum slice (a) the platinum lead be not set.Under pressure, unsintered alumina wafer (b) is overlapped on the unsintered alumina wafer, the well heater pattern is clipped between them and with two alumina wafer co-sintered.

Become the film in first and second middle layers when (3) being formed on sintering

Mixed weight is 80 parts alumina powder and 20 parts Zirconium oxide powder, and it is 5.5% yttria that the latter is contained molal quantity, as stabilizing agent.Add butyral resin and dibutyl ester phthalic acid salt with scheduled volume respectively for the potpourri of making, preparation cream.Cream is added in not on the sintering oxidation aluminum slice (b), forms first film, it becomes first middle layer (2a) when sintering.Subsequently, form second film (about 20 μ m are thick) with the similar manner that forms first film on first film, it becomes second middle layer (2b) when sintering, but when forming second film with 50 parts Zirconium oxide powder.

(4) form oxygen reference electrode pattern and the oxygen reference electrode leads is set

The oxygen reference electrode pattern that becomes oxygen reference electrode (4) and oxygen reference electrode head part (4a) during sintering is printed on second film with platinum cream, and subsequent drying forms the thick film of 20 μ m.The platinum lead is set then, has made the effect of oxygen reference electrode leads, the output transducer output signal.

(5) form a unsintered oxygen ionic conductive solid dielectric substrate, it becomes an oxygen ionic conductive solid dielectric substrate when sintering

Have high-purity mangesium oxide zirconium powder end 90 parts and 10 parts alumina powder mixing by weight by weight less than 0.1% pollutant, Zirconium oxide powder contain as stabilizing agent be 5.5% yttria with molal quantity, alumina powder has the pollutant less than 0.00%.The potpourri of making is added the butyl carbitol and the dibutyl ester phthalic acid salt of scheduled volume separately, preparation zirconia cream.Zirconia cream is added to oxygen and examines electrode model, is the not sintering oxygen ionic conductive solid dielectric substrate of 15 μ m thereby form thickness, subsequent drying.Then, similarly apply zirconia cream again twice, form thicker not sintering oxygen ionic conductive solid dielectric substrate (gross thickness is 45 μ m), when sintering this layer not sintering oxygen ionic conductive solid dielectric substrate become oxygen ionic conductive solid dielectric substrate (6).

(6) form potential electrode model and the potential electrode lead is set

The potential electrode model (becoming potential electrode (5) and potential electrode head 5a during sintering) that contains platinum cream prints to the surface of unsintered oxygen ionic conductive solid dielectric substrate, forms the thick film of 20 μ m, and is dry then.Then, the platinum lead is set makes it play potential electrode, from comprising electrolyte and electrolyte of electrodes battery output signal.

Become the pellumina of an aluminium oxide ceramics layer when (7) being formed on sintering

The aluminium oxide cream of preparation is applied on potential electrode model and the unsintered oxygen ionic conductive solid dielectric substrate in (1), and subsequent drying forms the thick film of about 20 μ m.Then, similarly apply aluminium oxide cream again twice, thereby become the pellumina (gross thickness is 60 μ m) of an aluminium oxide ceramics layer (7) when being formed on sintering.

(8) remove cementing agent and sintering

To be placed on atmospheric pressure by the layer structure that step (1) to (7) forms and continue to remove in 2 hours cementing agent for following 420 ℃.Then, under atmospheric pressure 1520 ℃ of co-sintered layer structures reach 1 hour.The layer structure that visual inspection is made like this (gas sensor element), particularly its end face.With the naked eye visual inspection judges whether gas sensor element has crackle, layer separation and warpage etc.

The aluminium oxide cream of preparation is applied on the alumina wafer in step (1), forms the film of 30mm (length) * 10mm (width) * 1mm (thickness), to remove cementing agent and sintering similar in appearance to the mode of step (8).The test specimens of making is by Archimedes's method density measurement, and discovery is 3.63g/cm ³, promptly the phase specific density with respect to solid density is 91.4%.The phase specific density of the aluminium oxide ceramics layer of this gas sensor element is about 91.4%.Example 2

Make gas sensor element and study the alumina content of oxygen ionic conductive solid dielectric substrate and the internal resistance of oxygen ionic conductive solid dielectric substrate between relation.

The zirconia powder of the alumina powder of purity 99.997% and the purity 99.95% of the yttria that contains molal quantity 5.5% mixes according to table 1.The potpourri of making adds butyl carbitol and dibutyl ester phthalic acid salt, spreading agent and the organic binder bond of each scheduled volume, thereby is prepared into zirconia cream.Use zirconia cream to make gas sensor element (1)-(14) similar in appearance to the mode of example 1.Gas sensor element (1)-(14) are assembled to each protection tube, and are exposed in the burning gas of town gas sintering generation, are set in the well heater no power in the alumina substrate simultaneously.According to the output of sensor, measure the internal resistance of some gas sensor elements of choosing from test specimens (1)-(14).Chew a mouthful temperature of measuring the burning gas of placing sample in the burning of coal gas, be defined as 600 ℃.The result is as follows.When oxygen ionic conductive solid dielectric substrate oxygen-free aluminium, clip the internal resistance of the electrode measurement of solid electrolyte between span centre, be about 0.2k Ω.At alumina content is 30% o'clock, and internal resistance is about 0.4k Ω.At alumina content is 50% o'clock, and internal resistance is about 0.6k Ω.At alumina content is 60% o'clock, and internal resistance is about 0.6k Ω.At alumina content is 70% o'clock, and internal resistance is about 0.7k Ω.At alumina content is 80% o'clock, and internal resistance is about 25-40k Ω.(wherein, the about 40 μ m of solid electrolyte layer of the own sintering that clips by two electrodes, the about 9mm2 of the area of each electrode) therefore, the maximal value limit of alumina content is 80% to gas sensor in the oxygen ionic conductive solid dielectric substrate, because the majority of gas sensor need be less than the spaning electrode internal resistance of 50k Ω, preferably less than 10k Ω.

Then, at 800 ℃ high temperature, according to the Cole-Cole figure line, measure sample (8) solid electrolyte itself in the table 1 resistivity.Resistivity is about 2 Ω m.

Table 1

Gas sensor element	Sintering temperature	Solid electrolyte layer characteristic (upper strata)
								Zirconia content weight %	Alumina content weight %	The life-span that autoclave quickens	Solid electrolyte feature (internal resistance)
????1	????1480	????90	????10	????○	????○
						????2	????1540	????90	????10	????○	????○
????3	????1540	????90	????10	????○	????○
						????4	????1480	????80	????20	????○	????○
????5	????1480	????70	????30	????○	????○
						????6 *	????1560	????70	????30	????×	????○
????7	????1480	????60	????40	????○	????○
						????8	????1490	????50	????50	????○	????○
????9	????1480	????40	????60	????○	????○
						????10	????1480	????30	????70	????○	????○
?? *11	????1660	????30	????70	????×	????○
						????12	????1480	????20	????80	????○	????○
?? *13	????1480	????10	????90	????×	????×
						?? *14	????1540	????100	????0	????×	????○

Annotate: in table 1 and 2, indicate ^*Sample, as simulating in the autoclave test, in harsh and unforgiving environments, as being not good as the performance of gas sensor of internal combustion engine that requires to stand-20 to+1000 ℃ thermal cycle.Even so, these samples still can use in other purposes, needn't remove from scope of the present invention.The test of example 3 autoclave life

The gas sensor element of sintering (1) that to obtain from the step (1) to (8) of example 1 is placed on the autoclave to (14), continues 6 hours under 200 ℃, 100% humidity and 15 atmospheric pressure.Arrive (14) adding water soluble red ink to gas sensor element (1) then, if crackle is arranged, just crackle is painted, thus the life-span estimated.The results are shown in the table 1.Crackle does not take place in " o " expression in the table 1, and crackle takes place in " x " expression.

As seen from Table 1, crackle does not take place in the alumina content scope by with appointment of the present invention.Example 4

Test in the autoclave life on two kinds of solid electrolytes (co-sintered).

The layer structure that integral sintered two kinds of solid electrolyte layers by different components (not sintering solid dielectric substrate) constitute, thus each of sample as shown in table 21 to 14 formed.Sample 1 to 14 is carried out the autoclave life test, estimate the life-span.

(1) manufacturing of sample, each sample is made of two kinds of different solid electrolyte layers

The lower floor of layer structure is with the printing of zirconia cream, and step (5) is described similar in the preparation of zirconia cream and the example 1, is oxygen-free aluminium (mean grain size of zirconia powder is 1.0 μ m).The layer size of having printed becomes a solid electrolyte layer for 0.04mm (thick) * 6mm * 6mm when sintering.The upper strata of layer structure is not use the printing of zirconia cream to form in the sintering lower floor, and zirconia cream contains zirconia and aluminium oxide, and their content is different (table 2 illustrates the mean grain size of zirconia powder and alumina powder) in sample 1 to 14.The printed layers size is 0.04mm (thick) * 5mm * 5mm, becomes a solid electrolyte layer when sintering.By these not the layer structure that constitutes of sintering solid dielectric substrate at the sintering (2 hours) in autoclave of temperature shown in the table 2.

To the average zirconia grain size on sample 1 to the 14 check upper strata of such sintering, it is calculated by preceding method.The results are shown in table 2.Table 2 also illustrates, and is 100% o'clock with the general assembly (TW) of zirconia and aluminium oxide, the zirconia of last solid electrolyte layer and alumina content.The last solid electrolyte layer oxygen-free aluminium of sample 14 in the table 2.

Table 2

Sample	The material powder characteristic		Sintering temperature	Solid electrolyte layer characteristic (upper strata)
									Zirconium oxide powder mean grain size (μ m)	Alumina powder mean grain size (μ m)		Zirconia mean grain size (μ m)	Zirconia content (weight %)	Alumina content (weight %)	The autoclave accelerated aging
????1	????0.6	????0.1	????1480	????1.8	????90	????10	????○
								????2	????0.6	????0.1	????1540	????1.8	????90	????10	????○
????3	????0.9	????0.3	????1540	????2.0	????90	????10	????○
								????4	????0.6	????0.3	????1480	????1.5	????80	????20	????○
????5	????0.6	????0.3	????1480	????1.3	????70	????30	????○
								?? *6	????2.3	????1.5	????1560	?? *2.6	????70	????30	????×
????7	????0.6	????0.3	????1480	????1.2	????60	????40	????○
								????8	????0.6	????0.4	????1490	????1.6	????50	????50	????○
????9	????0.6	????0.3	????1480	????0.9	????40	????60	????○
								????10	????0.6	????0.3	????1480	????0.8	????30	????70	????○
?? *11	????2.5	????2.5	????1560	?? *3.0	????30	????70	????×
								????12	????0.6	????0.3	????1480	????0.8	????20	????80	????○
?? *13	????2.3	????0.3	????1480	?? *2.8	????10	????90	????×
								?? *14	????1.2		????1540	????2.4	????100	?? *0	????×

(2) autoclave life test

Sample is placed autoclave, under 200 ℃, 100% humidity and 15 atmospheric pressure, continue 6 hours.Then to gas sensor element adding water soluble red ink, if as crackle, just crackle is painted, thus the life-span estimated according to coloring degree.The results are shown in the table 2.Crackle does not take place in " o " expression in the table 2, and crackle takes place in " x " expression.As shown in table 2, in sample 6,11 and 13, to see paintedly, the mean grain size of wherein surveying behind sintering is greater than 2.5 μ m, and shows crackle in the sample 14 of solid electrolyte layer oxygen-free aluminium.

Fig. 2 and 3 illustrates the sample 2 that stands autoclave life test and 3 photo.In Fig. 2 and 3, the center white portion is the solid electrolyte layer (upper strata) that contains zirconia and aluminium oxide, and the peripheral part that centers on the upper strata is the solid electrolyte layer (lower floor) of oxygen-free aluminium.Periphery is the obfuscation color, because crackle is painted.From these figure as seen, have salic solid electrolyte layer, and zirconic mean grain size is not more than and almost do not observe paintedly in any sample of 2.5 μ m, crackle does not take place in expression.Therefore, can think, be not more than in the solid electrolyte layer of 2.5 μ m, can suppress zirconic phase transformation effectively in salic and zirconic mean grain size.

(3) electron microscopic image

Take each sample 1,2,3,5 and 8 of making in the example 4 with electron microscope (JSM-5410 type, the product of JEOL Ltd.) at 5000 times.Fig. 4 to 8 illustrates these photos.Particularly, Fig. 4 is corresponding with sample 1; Fig. 5 is corresponding with sample 2; Fig. 6 is corresponding with sample 3; Fig. 7 is corresponding with sample 5; Fig. 8 is corresponding with sample 8.For comparison, the surface of sample 14, promptly the surface of the solid electrolyte layer of oxygen-free aluminium also similarly uses electron microscope 5000 times of shootings.Fig. 9 illustrates this photo.

In Fig. 4 to 8, white crystal grain is zirconic, and black crystal grain is aluminium oxide.In Fig. 9, black partly is following recess.From these figure as seen, compare with the zirconia mean grain size in the solid electrolyte layer of Fig. 9 of oxygen-free aluminium, the zirconic mean grain size in Fig. 4 to 8 is suppressed in quite low level.

A kind of ceramic laminar structure according to an aspect of the present invention produces following advantage.High-purity zirconia and high-purity insulating ceramics (particularly aluminium oxide) of mean grain size have separately been controlled by in solid electrolyte layer, adding, and keep being not more than the zirconia mean grain size of 2.5 μ m and less than 1.0 μ m aluminium oxide mean grain sizes, growing up of zirconia crystal grain obviously suppressed in solid electrolyte layer, suppresses zirconic phase transformation effectively.And, even substrate, solid electrolyte layer, electrode, protective seam and well heater sintering integratedly presses down the crackle of brush solid electrolyte layer quite effectively.Even behind sintering, the ceramic laminar structure of making in any environment is stable, thereby prevents the crackle of solid electrolyte layer.The manufacture method of above-mentioned aspect can conveniently be stablized to make and has the ceramic laminar structure of above-mentioned premium properties according to the present invention.And when forming the carrier of oxygen sensor element with ceramic laminar structure of the present invention, the carrier of oxygen sensor element can be the thick film lambda sensor element of any kind, as ICP, or introduces the reference gas build, or a large amount of lambda sensor.

The invention is not restricted to the foregoing description.Do not depart from scope of the present invention,, various scheme of the present invention can be arranged according to application.For example, alumina substrate and oxygen ionic conductive solid dielectric substrate can be salic, zirconia and the outer pottery of yttria.Can be on a surface of dielectric substrate, or form electrode in the electrolytical mode of therebetween.Can in co-sintered electrolyte, ceramic substrate, form electrode.Also available hafnia or hafnia and zirconic potpourri replace zirconia to make the electrolysis material.

The application is a basis, and full explanation is the flat 11-26733 of the registration in 3 days February in 1999 of reference in full, the Japanese patent applications such as flat 11-375846 of the flat 11-375808 of registration on Dec 28th, 1999 and registration on Dec 28th, 1999.

Claims (36)

1. gas sensor, comprise an electrochemical cell of measuring gas concentration, it comprises an oxygen ionic conductive solid dielectric substrate and the metal electrode that is formed on the oxygen ionic conductive solid dielectric substrate, and wherein the oxygen ionic conductive solid dielectric substrate contains the insulating ceramics crystal grain of weight 10-80%.

2. gas sensor according to claim 1 is characterized in that also comprising: a ceramic substrate, it and oxygen ionic conductive solid dielectric substrate hierarchically integrally combine.

3. gas sensor according to claim 1 is characterized in that the oxygen ionic conductive solid dielectric substrate contains the solid electrolyte ceramic that weight is 20-90%.

4. gas sensor according to claim 1 is characterized in that the solid electrolyte ceramic that contains contains the stabilizing agent of weight below 10% in the oxygen ionic conductive solid dielectric substrate.

5. gas sensor according to claim 1, the mean grain size that it is characterized in that the solid electrolyte ceramic that contains in the oxygen ionic conductive solid dielectric substrate is not more than 2.5 μ m, and the mean grain size of the insulating ceramics crystal grain that contains in the oxygen ionic conductive solid dielectric substrate is not more than 1 μ m.

6. gas sensor according to claim 1 is characterized in that at 600 ℃ interelectrode resistance less than 5k Ω.

7. gas sensor according to claim 1 is characterized in that at 600 ℃ interelectrode resistance less than 1k Ω.

8. gas sensor according to claim 2, it is characterized in that, also be included in the intermediate ceramic layer between oxygen ionic conductive solid dielectric substrate and insulating ceramics substrate, wherein the whole co-sintered of insulation course, middle layer and oxygen ionic conductive solid dielectric substrate forms a stratiform structure.

9. gas sensor according to claim 8 is characterized in that intermediate ceramic layer contains electrolyte ceramics and insulating ceramics, and the insulating ceramics weight that contains in intermediate ceramic layer high by 10% than in the oxygen ionic conductive solid dielectric substrate at least.

10. gas sensor according to claim 2 is characterized in that, comprises that also a phase specific density that is formed on the metal electrode is the ceramic layer of 60-99.5%, and described metal electrode is formed on the oxygen ionic conductive solid dielectric substrate.

11. gas sensor according to claim 1 is characterized in that, the metal electrode that is formed on the oxygen ionic conductive solid dielectric substrate comprises Pt.

12. gas sensor according to claim 1 is characterized in that, the insulating ceramics crystal grain that contains in the oxygen ionic conductive solid dielectric substrate comprises aluminium oxide.

13. gas sensor according to claim 1 is characterized in that, also comprises: an alumina substrate forms the oxygen ionic conductive solid dielectric substrate on described alumina substrate; A well heater is positioned at alumina substrate; An oxygen reference electrode is formed on the oxygen ionic conductive solid dielectric substrate; With a gasmetry electrode, be formed on the oxygen ionic conductive solid dielectric substrate; Wherein the oxygen ionic conductive solid dielectric substrate contains zirconia and aluminium oxide, and the weight that is contained in alumina grain in the oxygen ionic conductive solid dielectric substrate is the 10-80% of oxygen ionic conductive solid dielectric substrate general assembly (TW).

14. gas sensor according to claim 13 is characterized in that, the weight of alumina grain is the 30-70% of oxygen ionic conductive solid dielectric substrate weight.

15. gas sensor according to claim 13, it is characterized in that, also be included in a middle layer between alumina substrate and oxygen ionic conductive solid dielectric substrate, it is characterized in that, different in middle layer house zirconia and the insulating ceramics, the insulating ceramics content in the middle layer and oxygen ionic conductive solid dielectric substrate.

16. gas sensor according to claim 15 is characterized in that, the insulating ceramics weight content in the middle layer is bigger by 10% than the weight content of the insulating ceramics in the oxygen ionic conductive solid dielectric substrate at least.

17. gas sensor according to claim 2 is characterized in that, the main material that contains in the insulating ceramics substrate is an aluminium oxide.

18. gas sensor according to claim 13 is characterized in that also comprising the ceramic layer that is formed on gasmetry electrode and/or the oxygen ionic conductive solid dielectric substrate, it has the phase specific density of 60-99.5%.

19. gas sensor according to claim 18 is characterized in that, also comprises a gas defence layer, is formed on the outside surface of ceramic layer, prevents that the gasmetry electrode poisoned by extraneous element.

20. gas sensor according to claim 19 is characterized in that, the gas defence layer contains spinel.

21. gas sensor according to claim 1 is characterized in that, the insulation crystal grain that contains in the oxygen ionic conductive solid dielectric substrate is the product of making greater than 99.9% aluminium oxide from purity.

22. a method of making gas sensor comprises step: form aluminium oxide, zirconia and yttrium oxide powder potpourri; On the not sinter layer that potpourri forms, place two non sintered metal electrodes; With with described layer, two not sintered electrode and insulating substrate simultaneously at 1350-1600 ℃ of sintering, formation has a kind of ceramic laminar structure of the oxide ion conduction battery of oxygen ionic conductive solid dielectric substrate, described oxygen ionic conductive solid dielectric substrate transferable oxonium ion between the electrode of sintering, wherein the oxygen ionic conductive solid dielectric substrate contains the alumina grain of weight 10-80% and the zirconia by the part or all of stabilization of yttria of 20-90%.

23., it is characterized in that according to the described method of claim 22, constitute the zirconia and the yttria of mixture of powders, obtain by co-precipitation in a kind of liquid, described liquid contains the alkoxide of a kind of zirconia alkoxide and a kind of yttria.

24., it is characterized in that aluminium oxide has the purity greater than 99.9% according to the described method of claim 22.

25., it is characterized in that zirconia and yttria powder are that purity is greater than 99.99% according to the described method of claim 22.

26. solid electrolyte ceramic body, the electrolyte ceramics that contains insulating ceramics crystal grain and part or whole stabilization, wherein ceramic body contains the insulating ceramics crystal grain of weight 10-80%, described insulating ceramics crystal grain has, and is distributed in partly or the mean grain size that is not more than 1 μ m in the electrolyte ceramics of whole stabilization.

27. solid electrolyte ceramic body according to claim 26 is characterized in that, insulating ceramics crystal grain is that purity is at least 99.9% alumina grain.

28. solid electrolyte ceramic body according to claim 26 is characterized in that, the purity of alumina grain at the crystal grain center greater than 99.99%.

29. solid electrolyte ceramic body according to claim 26 is characterized in that, the electrolyte ceramics of part or whole stabilization contains the zirconia that weight is part or the whole stabilization of 20-90%.

30. solid electrolyte ceramic body according to claim 26 is characterized in that the electrolyte ceramics of part or whole stabilization comprises that mean grain size is not more than the zirconia of 2.5 μ m.

31. solid electrolyte ceramic body according to claim 26 is characterized in that, the ceramic body resistivity of measuring down 800 ℃ in atmospheric pressure are less than 10 Ω m.

32. solid electrolyte ceramic body according to claim 26 is characterized in that, the ceramic body resistivity of 800 ℃ of measurements is less than 5 Ω m.

33. solid electrolyte ceramic body according to claim 26 is characterized in that, the ceramic body resistivity of 800 ℃ of measurements is less than 2 Ω m.

34. solid electrolyte ceramic body according to claim 26, it is characterized in that, when 800 ℃ of measured resistivity, ceramic body resistivity is than five times little of the resistivity of solid electrolyte body, described solid electrolyte body contains the electrolyte ceramics of roughly the same part or whole stabilization, and contains the insulating ceramics crystal grain of weight 50%.

35. solid electrolyte ceramic body according to claim 26 is characterized in that, two metal electrodes are formed on the ceramic body, form an a kind of electrochemical cell of measuring a kind of gas.

36. solid electrolyte ceramic body according to claim 26 is characterized in that, two metal electrodes are formed on the ceramic body, form a kind of electrochemical cell of a measurement from a kind of gas composition of internal combustion engine discharge.

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