DE102009000319A1 - Resistive particle sensor, preferably resistive oxygen sensor for detecting particles in gas stream, comprises electrode system with two electrodes, and semiconducting material, where semiconducting material is contacted with electrodes - Google Patents

Abstract

A resistive particle sensor (1) comprises an electrode system (2) with two electrodes (3,4), and a semiconducting material (5), where the semiconducting material is contacted with the electrodes. The semiconducting material is selected from a group consisting of rare-rare-earth mixed oxides, rare earth-zirconium mixed oxides, alkaline earth metal-zirconium mixed oxides, transition metal-zirconium mixed oxides, rare earth-aluminum mixed oxides, alkaline earth metal-aluminum mixed oxides or transition metal-aluminum mixed oxides. A resistive particle sensor comprises an electrode system with two electrodes, and a semiconducting material, where the semiconducting material is contacted with the electrodes. The semiconducting material is selected from a group consisting of rare-rare-earth mixed oxides, rare earth-zirconium mixed oxides, alkaline earth metal-zirconium mixed oxides, transition metal-zirconium mixed oxides, rare earth-aluminum mixed oxides, alkaline earth metal-aluminum mixed oxides, transition metal-aluminum mixed oxides, rare earth-titanium mixed oxides, barium-titanium mixed oxides, transition metal-titanium mixed oxides, rare earth indium mixed oxides, alkaline earth metal indium mixed oxides, transition metal-indium mixed oxides, rare earth-zinc mixed oxides, alkaline earth-zinc mixed oxides, transition metal-oxide-mixed oxide, samarium, yttrium oxide, terbium oxide or their mixtures. An independent claim is also included for a method for producing resistive particle sensor, which includes creating oxidizing agent and/or reducing agent-free atmosphere.

Description

The The present invention relates to a particle sensor, a method for its production and a method for its operation.

State of the art

In In the near future, particle emissions, especially of vehicles, have to be addressed while the driving operation, after passing through an engine or Diesel Particulate Filter (DPF) monitored by law and the functionality this monitoring be ensured (on-board diagnostics, OBD). Furthermore is a load forecast of diesel particulate filters for regeneration control necessary to ensure high system security with few efficient, to ensure fuel-efficient regeneration cycles and cost-effective filter materials, For example, cordierite, to be able to use.

A possibility resistive particle sensors offer this. Resistive particle sensors have an electrode system with at least two, the exhaust gas freely exposed to metallic electrodes. In so-called interdigital electrode systems At least two comb-like electrodes engage each other. Under the influence of a voltage applied to the electrodes and In the resulting electric field, the ones to be detected are deposited Particles, in particular soot particles, at or between the electrodes, which starts at a certain level Particle quantity to a short circuit of the electrodes and thus to a Resistance and / or impedance change between the electrodes, which conclusions on the particle attachment allows.

There in use for on-board diagnosis of the particle sensor behind the diesel particulate filter is installed, are at full function of the filter at the position of the particle sensor no particles in the Exhaust gas that could generate a particulate sensor signal. No However, signal can also mean that the particle sensor is defective is and therefore does not recognize a likewise defective filter.

to Determination of the oxygen content in the exhaust gas of internal combustion engines Lambda probes are used. Monitor the widely used binary lambda probes on the basis of the Nernst principle the observance of a constant Lambda value λ = 1, at which these probes their greatest sensitivity exhibit. However, these probes have a low in the lean range (λ> 1) Sensitivity, why these probes are used to measure larger lambda ranges, for example, λ = 0.8 to air, which for example in lean-burn engines, such as direct injection and diesel engines is required are not suitable.

resistive Lambda probes, represent an alternative to this. Resistive lambda probes have a mixed oxide ceramic whose electrical resistance with enough high temperatures, for example, from 600 ° C to 1100 ° C, the oxygen content of surrounding atmosphere is dependent and as a measure of the oxygen content can be used. Resistive lambda sensors are only not very common, because on the one hand a high temperature dependence resistance, and the chemical stability of many semiconducting materials under exhaust conditions are insufficient.

Disclosure of the invention

object The present invention is a resistive particle sensor which an electrode system of at least two electrodes and at least a semiconductive material that contacts the electrodes, and characterized in that the semiconductive Material at least one oxide selected from the group consisting of Rare earth-rare earth mixed oxides, rare earth-zirconium mixed oxides, Alkaline earth-zirconium mixed oxides, transition metal-zirconium mixed oxides, Rare earth-aluminum mixed oxides, alkaline earth-aluminum mixed oxides, transition metal-aluminum mixed oxides, Rare earth titanium mixed oxides, barium titanium mixed oxides, transition metal titanium mixed oxides, rare earth indium mixed oxides, alkaline earth indium mixed oxides, transition metal indium mixed oxides, Rare earth zinc mixed oxides, alkaline earth zinc mixed oxides, transition metal zinc oxide mixed oxides, Samarium oxide, yttrium oxide, terbium oxide and / or mixtures thereof, includes or consists of.

Under The term "particles" can be used in the Purpose of the present invention gaseous, solid and / or liquid particles be understood. In particular, in the context of the present Invention by the term "particles" conductive particles, like soot particles, and / or conductive Droplets and / or Oxygen can be understood.

In the context of the present invention, the term "mixed oxide" can be understood as meaning a mixture of at least two oxides of different elements. In particular, in the context of the present invention, the term "mixed oxide" can be understood as meaning a mixture of at least two oxides of different elements, in which the stoichiometric proportion of the individual oxides is substantially of the same order of magnitude. For example, in a mixed oxide, the ratio between the element with the largest stoichiometric amount and one of the other element in a range of 1: 1 to 1: 0.01.

Under The term "contact" may be in the sense in particular, the semiconducting Material contacted the electrodes such that the electrodes on the semiconducting material are electrically conductively connected.

The used according to the invention Materials have the advantage that they have a reversible oxygen incorporation or -ausbau and / or a good connection of the electrodes, especially of platinum-based electrodes, to the semiconducting Ensure material and / or high exhaust gas stability and / or a high resistance to aging can have.

Of the Particle sensor according to the invention has the advantage that this as a resistive particle sensor, as resistive liquid sensor and / or as an oxygen sensor, for example as a resistive lambda probe, can be used. In particular, the particle sensor according to the invention for the detection of conductive Particles, conductive Liquids and / or for determining the oxygen concentration in a gas stream, in particular in an exhaust gas of a combustion (kraft) machine, such as a Motor vehicle or an incinerator, are used. Advantageously, the particle sensor according to the invention is additionally based on a simple measuring principle and a simple and inexpensive Construction.

Within the scope of an embodiment of the particle sensor according to the invention, the particle sensor is a resistive particle sensor, in particular a soot particle sensor. Advantageously, in addition to the particle determination, in the context of a "self-diagnosis", the functionality, in particular intactness, of the particle sensor can be checked in the absence of particles deposited thereon. Therefore, the semiconductive material may also be referred to as a self-diagnostic material, for example, a self-diagnostic layer. The self-diagnosis function of the particle sensor can be based on the measurement of the conductivity, in particular on the basis of oxide ion and / or electron conduction, or the electrical resistance of the semiconductive material. The conductivity or the resistance of the semiconducting material can be determined by cathodic wiring of one electrode and anodic connection of the other electrode. Advantageously, the electrode system can be checked as a unit for the functionality and / or the sensitivity of the diagnostic method can be optimized. For use in a particle sensor, the semiconductive material preferably has low conductivity during the particle measurement phase and high conductivity during the diagnostic phase. For use in a particle sensor in particular semiconducting materials have proven to be advantageous whose conductivity or resistance is dependent on the temperature and the oxygen partial pressure and at self-diagnostic temperature, a suitable for diagnosis conductivity while maintaining sufficiently high Isolatoreigenschaften may have during particle measuring operation. For use in a particle sensor, the semiconducting material preferably has a temperature of ≥ 400 ° C., for example of ≥ 500 ° C., in particular of ≥ 550 ° C., and / or of a λ of ≥ 0.8, in particular of ≥ 1 , 1, has a specific electrical conductivity of ≥ 10 -5 S / m, for example of ≥ 10 ^-3 S / m, in particular of ≥ 0.1 S / m. By utilizing the temperature dependence and the oxygen interference, it is advantageously possible to achieve a high significance of the self-diagnostic measurement with known oxygen content of the exhaust gas.

Within the scope of another embodiment of the particle sensor according to the invention, the particle sensor is an oxygen sensor, in particular a resistive lambda probe. For use in a lambda probe, the semiconductive material preferably has a substantially constant electrical resistance value, at least in a temperature range, for example from ≥ 700 ° C. to ≦ 900 ° C. In this way, temperature fluctuations, for example due to changes in the flow, can advantageously be tolerated without these falsifying the measurement of the oxygen concentration. Furthermore, the semiconducting material for use in a lambda probe preferably has an unambiguous characteristic curve over the entire lambda range, that is to say λ = 0.8 to air, while at the same time having a low temperature dependence. For use in a lambda probe, the semiconducting material furthermore preferably has an oxygen sensitivity (m) R = R ₀ pO ₂ ^-m (m: 0.1-0.3). In this way, lambda jumps can lead to a change in resistance within an order of magnitude, which is why the measuring range can be designed correspondingly small.

In a preferred embodiment of the particle sensor according to the invention, the semiconductive material comprises at least one oxide selected from the group consisting of rare earth-rare earth mixed oxides, rare earth-zirconium mixed oxides, alkaline earth-zirconium mixed oxides, transition metal-zirconium mixed oxides, rare earth-titanium Mixed oxides, barium-titanium mixed oxides, transition metal-titanium mixed oxides, samarium oxide, yttrium oxide, terbium oxide and / or mixtures thereof. For example, the semiconducting material may consist of at least one oxide selects from this group.

in the Frame of a particularly preferred embodiment of the particle sensor according to the invention For example, the semiconductive material comprises at least one oxide selected from the group consisting of terbium-rare earth mixed oxides, Rare earth-zirconium mixed oxides, calcium-zirconium mixed oxides, lanthanum-zirconium mixed oxides, Barium-titanium mixed oxides, samarium oxide, yttrium oxide, terbium oxide and / or mixtures thereof. For example, the semiconducting Material thereby consist of at least one oxide selected from this group.

in the Frame of a further, particularly preferred embodiment the particle sensor according to the invention For example, the semiconductive material further comprises gadolinia.

Within the scope of a further, particularly preferred embodiment of the particle sensor according to the invention, the semiconductive material comprises at least one oxide selected from the group consisting of terbium-yttrium mixed oxides, terbium-samarium mixed oxides, terbium-gadolinium mixed oxides, terbium-yttrium-samarium mixed oxides , Terbium-yttrium-gadolinium mixed oxides, terbium-samarium-gadolinium mixed oxides, terbium-yttrium-samarium-gadolinium mixed oxides and / or mixtures thereof. For example, the semiconducting material may consist of at least one oxide selected from this group. Such semiconducting materials may be p-type, that is, the electrical resistance can decrease unequivocally with increasing oxygen content over the entire lambda range (λ> 0.8). In addition, such semiconducting materials can be distinguished by having a differentiable resistance (unambiguous characteristic) and / or an oxygen sensitivity m of ≥ 0.1 to ≦ 0.3 in a large lambda range, in particular from λ = 0.8 to air show which can be clearly assigned to an oxygen partial pressure. Such semiconductive materials may also have a lambda sensitivity from a temperature of about 400 ° C. The working temperature can therefore be selected between 400 ° C and 1000 ° C. These temperatures can be realized for example by a, in particular integrated heating device. Semiconducting materials of this kind can advantageously have a resistance plateau in the temperature range from ≥ 700 ° C. to ≦ 900 ° C. (see 2 ) exhibit. When operating as an oxygen sensor / lambda probe therefore offers a temperature at 800 ° C, since at this temperature a temperature fluctuation of ± 100 K, the measurement does not significantly affect the determination of the oxygen content (low cross-sensitivity to the temperature). Furthermore, such materials can have good adhesion to electrodes, in particular in the case of low or no interdiffusion or secondary phase formation, and / or high chemical stability, in particular in the lambda range λ> 0.8. In addition, such semiconducting materials can have a resistance behavior advantageous for the functional diagnosis of the sensor: for example, high impedance at low lambda values or low temperatures, for example in the case of a heater failure, and / or critically small lambda values at a sensor defect, for example a contact interruption. It is believed that the temperature dependence of the electrical resistance of these materials is based on a hopping line mechanism.

The specific resistance of the semiconducting material and the plateau can be advantageously adjusted via the proportion of terbium, yttrium, samarium and / or gadolinium (see 2 ).

• – der Anteil an Terbium von > 0% bis ≤ 90%, insbesondere von ≥ 1% bis ≤ 50%, und/oder
• – der Anteil an Yttrium von ≥ 0% bis ≤ 99%, insbesondere von ≥ 25% bis ≤ 99%, und/oder
• – der Anteil an Samarium von ≥ 0% bis ≤ 50%, insbesondere von ≥ 25% bis ≤ 50%, und/oder
• – der Anteil an Gadolinium von ≥ 0% bis ≤ 50%, insbesondere von ≥ 40% bis ≤ 50%,

bezogen auf die stöchiometrische Gesamtmenge, betragen, wobei die prozentualen Anteile der einzelnen Elemente derart ausgewählt werden, dass diese in Summe 100% ergeben.For example:

• The proportion of terbium from> 0% to ≤ 90%, in particular from ≥ 1% to ≤ 50%, and / or
• The proportion of yttrium from ≥ 0% to ≤ 99%, in particular from ≥ 25% to ≤ 99%, and / or
• - the proportion of samarium from ≥ 0% to ≤ 50%, in particular from ≥ 25% to ≤ 50%, and / or
• The proportion of gadolinium from ≥ 0% to ≤ 50%, in particular from ≥ 40% to ≤ 50%,

based on the stoichiometric total amount, wherein the percentage proportions of the individual elements are selected such that they add up to 100%.

In the context of a further, particularly preferred embodiment of the particle sensor according to the invention, the semiconducting material comprises samarium oxide, yttrium oxide, terbium oxide, barium titanate, La ₂ Zr ₂ O ₇ and / or CaZrO ₃ . In particular, the semiconducting material may consist of samarium oxide, yttrium oxide, terbium oxide, barium titanate, La ₂ Zr ₂ O ₇ and / or CaZrO ₃ . Preferably, the semiconductive material has a pyrochlore-like crystal structure. Semiconducting materials of this type have proven advantageous, in particular, for use in a resistive particle sensor.

The Semiconductive material can be used in the context of the present invention for example, as a ceramic sintered body, thick film, thin film, be executed ceramic film or conductor track.

Within the scope of a further, preferred embodiment of the particle sensor according to the invention, the particle sensor has a layer of the semiconducting material. The electrodensys Tem can be arranged on the layer of the semiconducting material. For example, the layer of the semiconductive material may partially or completely contact the electrode system.

in the Frame of a further preferred embodiment of the particle sensor according to the invention the particle sensor furthermore has an insulation layer. For example For example, the insulating layer may comprise alumina and / or glass, respectively consist of it. The layer of the semiconductive material can be arranged in particular on the insulating layer. Basically the layer of the semiconducting material, the insulating layer both completely as well as partially cover. Covered as part of a design the layer of the semiconducting material only a part of the insulating layer. In this way, advantageously, the sensor structure for a separate Wiring of the electrodes can be simplified.

in the Frame of a further preferred embodiment of the particle sensor according to the invention has at least one metal, for example zirconium, of the semiconducting one Materials in the areas of the semiconducting material which the Contact electrodes, at least partially a lower or higher Oxidation number on than the same metal in the other areas semiconducting material. Such an inventive embodiment may through the later explained Production method according to the invention be achieved and advantageously has an improved connection the electrode material, in particular platinum, to the semiconductive Material and improved conductivity result.

in the Frame of another embodiment of the particle sensor according to the invention the electrode system comprises at least three, in particular at least four, electrodes. For example, the resistance measurement means Two-wire, three-wire or four-wire measurement done.

in the Frame of a further preferred embodiment of the particle sensor according to the invention the electrode system is an interdigital electrode system of at least two comb-like interdigitated interdigital electrodes.

in the Frame of a further preferred embodiment of the particle sensor according to the invention The electrodes comprise a noble metal, for example platinum and / or Gold.

in the Frame of a further, particularly preferred embodiment the particle sensor according to the invention the electrodes are made of a cermet of at least one precious metal, in particular platinum, and formed the semiconducting material. For example may be the proportion of semiconducting material, based on the total weight of the Zermet, of ≥ 0.1 Weight percent up to ≤ 20 Percent by weight, in particular of ≥ 5 Weight percent up to ≤ 15 Percent by weight. This can be an improvement ensures the connection of the electrode to the semiconducting material become. In particular, this can advantageously already during the Production of the particle sensor, especially during sintering, a good Connection of the electrodes to the semiconducting material take place.

In the context of a further, particularly preferred embodiment of the present invention, the electrodes ( 3 . 4 ) has a porosity of ≥ 15%, for example from ≥ 5% to ≤ 20%. This has the advantage that oxygen can be easily tracked to the semiconducting material and no depletion of oxygen occurs.

in the Frame of a further, particularly preferred embodiment The present invention has the surface of the particle sensor, in particular semiconducting material, a partial or complete impregnation made with at least one metal, which combustible gases, in particular the reduction of oxygen to oxygen ions, catalyzed. Under an "impregnation" can thereby understood in the context of the present invention, a kind of coating which are spaced apart, for example, island-like, catalytic Metal areas based. In this way, the sensor according to the invention also be used for the determination of combustible gases, without while the electrodes directly over short circuit the catalytically active metal. For example, are suitable as catalytic metal platinum and / or palladium, in particular Platinum. An impregnation has the advantage that, especially when driving, bound oxygen while The self-diagnosis can be implemented more easily and thus a reduction of the semiconducting material during the operation of the particle sensor can be avoided.

in the Frame of a further preferred embodiment of the particle sensor according to the invention the particle sensor has leads and contacts for contacting of the electrodes. The supply lines and / or contacts can Noble metal, for example platinum and / or gold, include or from consist.

Within the scope of a further, preferred embodiment of the particle sensor according to the invention, the particle sensor comprises a carrier layer. The carrier layer can, for example, as Substrate for the semiconducting material and / or serve for the later-explained heater and / or temperature measuring device. The carrier layer may comprise or consist of, for example, aluminum oxide, zirconium oxide and / or magnesium oxide. Insofar as the carrier layer is formed from a conductive material, it is preferably spaced apart from the semiconducting material and the electrodes by at least one insulating layer.

in the Frame of a further, particularly preferred embodiment the particle sensor according to the invention the particle sensor comprises a temperature measuring device.

in the Frame of a further, particularly preferred embodiment the particle sensor according to the invention the particle sensor comprises a heating device. The heater can be based on a wire loop, a thick or thin film structure. The heating device can be made, for example, of an oxidation-resistant material, in particular platinum, be formed. Preferably, the heater is at least over an insulating layer of the semiconducting material and the electrodes separated.

One Another object of the present invention relates to a method for producing a particle sensor according to the invention, by under an oxidant and / or reducing agent-free, especially oxygen-free, atmosphere a voltage to the electrodes and the semiconductive material is applied, the voltage being such chosen is that at least one metal, such as zirconium, the semiconducting material in the areas of the semiconductive material, which contact the electrodes, at least partially reduced or oxidized. The method according to the invention has the advantage that the one or more metals, in particular zirconium, of the semiconducting Materials at the transition partially between the electrodes and the semiconductive material to lower valence states reduced or higher valence is oxidized, resulting in an improved connection of the electrode material to the semiconductive material and improved conductivity results.

The Production method according to the invention can be carried out, for example, under a nitrogen atmosphere. Appropriately, will the inventive method performed at a temperature, in which the semiconductive material is conductive. For the reduction of a metal can the electrodes be connected as cathodes. It is in the frame of the present invention both possible both electrodes simultaneously with the same potential the semiconducting material as well as the electrodes one after the other with a potential opposite to connect the semiconducting material.

The Production method according to the invention can advantageously be used as part of the basic test or as a 100% exam designated, final review of a by a conventional Procedure produced particle sensor done.

The Forming the interdigital electrode system and the semiconducting one Material can be used in the context of the manufacturing method of the invention over conventional For the production of particle sensors known methods, for example by a screen printing process.

in the Frame of a preferred embodiment of the production method according to the invention the method further comprises the step of: partially or completely impregnating the surface the particle sensor, in particular the semiconducting material, with at least one metal containing combustible gases, in particular the reduction from oxygen to oxygen ions, catalyzed. For example, are suitable this is platinum and / or palladium, in particular platinum. The Impregnate can be done for example by the fact that the particle sensor with one, in particular low concentrated, sprayed solution of the metal or is immersed in such.

One Another object of the present invention is a particle sensor prepared by the production process according to the invention.

One Another object of the present invention is a method for the self-diagnosis of a particle sensor according to the invention, in particular one Resistive particle sensor, in a self-diagnosis phase: on the electrodes are applied with a voltage; and the resulting conductivity or the resulting electrical resistance measured and re the temperature measured by a temperature measuring device and the oxygen partial pressure measured by an oxygen meter is compensated; and the resulting result as a measure of the function of the particle sensor is output.

The temperature can be measured, for example, by the temperature measuring device of the particle sensor. The oxygen partial pressure can be determined, for example, by an oxygen sensor, for example a (broadband) lambda probe, which is connected in front of the particle sensor in particular. After compensation of the electrical conductivity or the electrical resistance with respect to its dependence on Tempe Temperature and oxygen partial pressure can advantageously be made a statement about the state of the particle sensor. In particular, any damage can be detected and the integrity of the particle sensor can be checked.

drawings

Further Advantages and advantageous embodiments of the subject invention are illustrated by the drawings and in the following description explained. It should be noted that the drawings are only descriptive in nature and are not meant to be the invention in any way Restrict shape. It demonstrate

1a a schematic plan view of an embodiment of a particle sensor according to the invention;

1b a schematic cross section through the in 1a shown embodiment of a particle sensor according to the invention;

2 a graph illustrating the temperature dependence of the resistivity of several terbium mixed oxides;

3 a graph illustrating the temperature dependence of the resistance absolute values of several terbium mixed oxides;

4 a graph illustrating the electrical resistance of a terbium-yttrium mixed oxide as a function of lambda at different sample temperatures; and

5 a graph illustrating the long-term stability of a terbium-yttrium mixed oxide under periodic Lambda load.

The 1a and 1b show that the particle sensor according to the invention 1 in the context of this embodiment, an interdigital electrode system 2 with two interdigital electrodes 3 . 4 and a semiconducting material 5 which comprises the interdigital electrodes 3 . 4 contacted. The 1a and 1b show in particular that, the particle sensor according to the invention 1 in the context of this embodiment layer of the semiconductive material 5 wherein the interdigital electrode system 2 on the layer of semiconducting material 5 is arranged and the layer of the semiconductive material 5 the interdigital electrode system 2 completely contacted. The 1a and 1b further show that the particle sensor according to the invention 1 in the context of this embodiment, an insulating layer 6 on which the layer of the semiconductive material 5 is arranged. As part of the in the 1a and 1b embodiment shown covers the layer of the semiconductive material 5 only under the electrode system 2 arranged region of the insulating layer 6 , As a result, advantageously, the particle sensor structure for a separate wiring of the electrodes 3 . 4 be simplified. The 1a and 1b show, moreover, that the particle sensor according to the invention 1 in the context of this embodiment leads 7 . 8th and contacts 9 . 10 for contacting the electrodes 3 . 4 having.

2 illustrates the temperature dependence of the resistivity of several terbium mixed oxides. The measuring geometry for recording the in 2 The data presented was essentially the same as in the 1a and 1b shown. The reference number 11 indicates the measurement data of a terbium-yttrium-samarium mixed oxide comprising 50% terbium, 25% yttrium and 25% samarium. The reference number 12 identifies the measurement data of a terbium yttrium-samarium mixed oxide comprising 30% terbium, 25% yttrium and 45% samarium. The reference number 13 indicates the measurement data of a terbium-gadolinium mixed oxide comprising 30% terbium and 70% gadolinium. The reference number 14 identifies the measurement data of a terbium-yttrium mixed oxide comprising 30% terbium and 70% yttrium. The reference number 15 identifies the measurement data of a terbium-yttrium mixed oxide comprising 10% terbium and 90% yttrium. The reference number 16 denotes the measurement data of a terbium-yttrium mixed oxide comprising 3% terbium and 97% yttrium. 2 shows that with a suitable material composition, the initially exponential temperature dependence of the resistivity at high temperatures opens in a plateau.

3 illustrates the temperature dependence of the resistance absolute values of several terbium mixed oxides. The absolute values of the resistance were measured on a thick layer of mixed oxides. The reference numerals denote those associated with 2 explained mixed oxides. Except for the measured values at 700 ° C, all measured values were measured in air with an oxygen content of 20%. Only at 700 ° C was measured both at an oxygen content of 20% and 1%. The scatter bars characterize in 3 the oxygen partial pressure dependence of the resistance when changing from an oxygen content of 20% to an oxygen content of 1%. 2 shows that the oxygen dependence is maintained in the temperature plateau.

4 illustrates the electrical resistance of a terbium-yttrium mixed oxide comprising 5% terbium and 95% yttrium as a function Lambda at different sample temperatures. The measurement was made on a thick-film sample. The heating of the sample was carried out in air. The repetitive lambda jumps ( 0.8 . 0.9 . 1.1 ; 1.3 ) was realized by the basic oxygen partial pressure of 3% O ₂ . 4 shows that lambda jumps lead to a change in resistance within an order of magnitude. The measuring range can therefore advantageously be designed correspondingly small.

5 illustrates the long-term stability of a terbium-yttrium mixed oxide comprising 10% terbium and 90% yttrium under periodic lambda loading. 5 shows the resistance of a thick film sensor based on this terbium yttrium mixed oxide as a function of periodic lambda jumps ( 1 . 3 ; 1 . 1 ; 0 . 8th ) at 700 ° C. 5 shows that no aging effects could be observed in the time interval of about 24 hours, which indicates a high chemical stability of the material under exhaust gas conditions.

Claims (17)

Resistive particle sensor ( 1 ) for the detection of particles in a gas stream, comprising - an electrode system ( 2 ) from at least two electrodes ( 3 . 4 ), and - at least one semiconducting material ( 5 ), the semiconducting material ( 5 ) the electrodes ( 3 . 4 ), characterized in that the semiconductive material ( 5 ) at least one oxide selected from the group consisting of rare earth-rare earth mixed oxides, rare earth-zirconium mixed oxides, alkaline earth-zirconium mixed oxides, transition metal-zirconium mixed oxides, rare earth-aluminum mixed oxides, alkaline earth-aluminum mixed oxides, transition metal-aluminum Mixed oxides, rare earth-titanium mixed oxides, barium-titanium mixed oxides, transition metal-titanium mixed oxides, rare earth-indium mixed oxides, alkaline earth-indium mixed oxides, transition metal-indium mixed oxides, rare earth-zinc mixed oxides, alkaline earth-zinc mixed oxides Transition metal-zinc oxide mixed oxides, samarium oxide, yttrium oxide, terbium oxide and / or mixtures thereof. Particle sensor ( 1 ) according to claim 1, characterized in that that of the particle sensor, the particle sensor is a resistive particle sensor and / or a resistive lambda probe. Particle sensor ( 1 ) according to claim 1 or 2, characterized in that the semiconductive material ( 5 ) at least one oxide selected from the group consisting of rare earth-rare earth mixed oxides, rare earth-zirconium mixed oxides, alkaline earth-zirconium mixed oxides, transition metal-zirconium mixed oxides, rare earth-titanium mixed oxides, barium-titanium mixed oxides, transition metal-titanium Mixed oxides, samarium oxide, yttria, terbia and / or mixtures thereof. Particle sensor ( 1 ) according to one of claims 1 to 3, characterized in that the semiconductive material ( 5 ) at least one oxide selected from the group consisting of terbium-rare earth mixed oxides, rare earth-zirconium mixed oxides, calcium-zirconium mixed oxides, lanthanum-zirconium mixed oxides, barium-titanium mixed oxides, samarium oxide, yttrium oxide, terbium oxide and / or mixtures of which includes. Particle sensor ( 1 ) according to one of claims 1 to 4, characterized in that the semiconductive material ( 5 ) further comprises gadolinium oxide. Particle sensor ( 1 ) according to one of claims 1 to 5, characterized in that the semiconductive material ( 5 ) at least one oxide selected from the group consisting of terbium-yttrium mixed oxides, terbium-samarium mixed oxides, terbium-gadolinium mixed oxides, terbium-yttrium-samarium mixed oxides, terbium-yttrium-gadolinium mixed oxides, terbium-samarium-gadolinium Mixed oxides, terbium-yttrium-samarium-gadolinium mixed oxides and / or mixtures thereof. Particle sensor ( 1 ) according to claim 6, characterized in that - the proportion of terbium from> 0% to ≤ 90%, and / or - the proportion of yttrium from ≥ 0% to ≤ 99%, and / or - the proportion of samarium of ≥ 0% to ≤ 50%, and / or - the proportion of gadolinium from ≥ 0% to ≤ 50%, based on the total stoichiometric amount is, wherein the percentage of the individual elements are selected such that they add up to 100% , Particle sensor ( 1 ) according to one of claims 1 to 6, characterized in that the semiconductive material ( 5 ) Comprises samarium oxide, yttrium oxide, terbium oxide, barium titanate, La ₂ Zr ₂ O ₇ and / or CaZrO ₃ . Particle sensor ( 1 ) according to one of claims 1 to 8, characterized in that the electrodes ( 3 . 4 ) of a cermet of at least one precious metal and the semiconducting material ( 5 ) are formed. Particle sensor ( 1 ) according to one of claims 1 to 9, characterized in that the proportion of semiconducting material ( 5 ), based on the total weight of the cermet, of ≥ 0.1 weight per zent to ≤ 20 percent by weight. Particle sensor ( 1 ) according to one of claims 1 to 10, characterized in that the electrodes ( 3 . 4 ) have a porosity of ≥ 15%. Particle sensor ( 1 ) according to one of claims 1 to 11, characterized in that the electrode system ( 2 ) an interdigital electrode system ( 2 ) of at least two comb-like interdigitated interdigital electrodes ( 3 . 4 ). Particle sensor ( 1 ) according to one of claims 1 to 12, characterized in that the surface of the particle sensor comprises a partial or complete impregnation of at least one metal which catalyzes flammable gases. Method for producing a particle sensor ( 1 ) according to one of claims 1 to 13, characterized in that, under an oxidant and / or reducing agent-free, atmosphere, a voltage to the electrodes ( 3 . 4 ) and the semiconducting material ( 5 ), wherein the voltage is chosen such that at least one metal of the semiconducting material ( 5 ) in the areas of the semiconducting material ( 5 ), which the electrodes ( 3 . 4 ), at least partially reduced or oxidized. Method according to claim 14, characterized in that that the method further the method step: partial or complete Impregnate the surface of the particle sensor with at least one metal which is combustible Catalyzes gases. Particle sensor made by a method according to claim 14 or 15. Method for self-diagnosis of a particle sensor ( 1 ) according to one of claims 1 to 13, by applying in a self-diagnosis phase to the electrodes ( 3 . 4 ) a voltage is applied; and the resulting conductivity or electrical resistance is measured and compensated for the temperature measured by a temperature measuring device and the oxygen partial pressure measured by an oxygen measuring device; and the resulting result is output as a measure of the function of the particle sensor.