DE102010063529A1 - heating element - Google Patents

Abstract

A sensor element (110) and a heating element (112), in particular for use in a sensor element (110), are proposed. The sensor element (110) can in particular be designed to detect at least one property of a gas in a measurement gas space. The heating element (112) comprises at least two contact elements (120) and at least two heating paths (126, 128) to which a heating current can be applied via the contact elements (120). The heating element (112) is designed in such a way that a total current provided via the contact elements (120) is divided into the heating paths (126, 128) in different ways at at least two different temperatures.

Description

State of the art

Numerous components or assemblies are known from the prior art, which have one or more heating elements for producing one or more operating temperatures, for example integrated heating elements. Without limiting further possible embodiments and fields of application, the invention will be described below with reference to heating elements in sensor elements for detecting at least one property of a gas in a measuring gas space. In particular, the sensor elements may be sensor elements which are set up for the qualitative and / or quantitative detection of a gas in a measurement gas space, in particular a ceramic sensor element, for example with one or more functional ceramics. Examples of such sensor elements, to which the invention is not limited, are sensor elements in which at least two electrodes are provided, which are interconnected via at least one solid electrolyte, in particular a ceramic solid electrolyte such as zirconia, in particular yttrium-stabilized zirconia or scandium-doped zirconia. Embodiments of such sensor elements are in Robert Bosch GmbH: Sensors in the motor vehicle, issue 2007, pages 154-159 described. The at least one gas component whose proportion in the gas is to be detected qualitatively and / or quantitatively can be, in particular, oxygen and / or nitrogen oxides and / or hydrocarbons. However, other gas shares can also be recorded in principle.

The generally existing need to use one or more heating elements in such exhaust gas sensors, which are constructed on the basis of functional ceramics, usually results from the fact that the functional ceramics an operating temperature of typically 700 to 900 ° C, for example 800 ° C, need. Typically, therefore, one or more platinum heaters are provided in such sensor elements, for example sensor elements with a ceramic layer structure. Such platinum heaters are designed, for example, as Heizmäander. In this case, different requirements are placed on the heating resistor of the heating elements. Thus, at low temperatures, the heater should exceed a minimum resistance. As a result, the output stages of a control device of the sensor element can usually be designed for lower currents. At high temperatures, however, the heating element should fall below a maximum resistance. In this case, even with a limited heating voltage, for example a maximum heating voltage of 10.5 V, sufficient heating power can be transferred into the sensor element.

Due to the above requirements and the temperature dependence of conventional heating element materials, such as platinum, however, there are generally strict restrictions in practice with respect to the geometric design of the heating element. In some applications, the use of another heater metal, such as another heater alloy, is essential, so that, for example, in many lambda probes, in particular lambda probes for diesel applications, in many cases Pt / Pd heaters are used. However, this results in further challenges regarding an encapsulation of the heating element. In general, it would be desirable to reduce the proportion of noble metals, in particular platinum, in the entire sensor element and in particular also in the heating element. From the prior art, for example WO 2007/062969 A1 , is basically known to design heating elements such that two heaters are connected in parallel. Furthermore, the use of perovskites as electrically conductive materials is generally known and also in exhaust gas probes, for example WO 2001/044798 A1 , Despite the improvements achieved by these known embodiments, however, there is still a need for improvement, in particular with regard to the above-described different requirements for the heating elements and with regard to the general precious metal requirement of the heating elements.

Disclosure of the invention

Therefore, a heating element and a sensor element for detecting at least one property of a gas in a measuring gas space are proposed, which at least largely avoid the abovementioned disadvantages of known heating elements and sensor elements. As described above, the at least one property of the gas in a measurement gas space can basically be any physically and / or chemically measurable property. It is particularly preferred if the at least one property comprises a portion of a gas component in the gas, so that the sensor element can be set up in particular for the qualitative and / or quantitative detection of the gas component. However, other applications are possible in principle.

The heating element comprises at least two contact elements and at least two heating paths which can be acted upon by the contact elements with heating current. It is particularly preferred if exactly two contact elements are provided, wherein, for example, a heating voltage source and / or current source can be connected to the heating paths via the two contact elements. The heating paths can be Share generally at least one of the contact elements, so that, for example, a contact element is provided for at least two Heizpfade. For example, two contact elements may be provided, which are each connected to at least two Heizpfaden. Under a contact element is generally an element to understand, via which the Heizpfade can be acted upon by an electric current and / or an electrical voltage. The contact elements may include, for example, contact pads for connecting corresponding contacts and / or also supply lines which are connected to the heating paths. Under a heating path is basically any conductor arrangement to understand, which is adapted to generate when exposed to a voltage and / or current heat or heating power. In particular, the heating paths can be printed heating paths of a layer structure, in particular of a ceramic layer structure. The heating paths may preferably have a non-straight configuration equipped with one or more windings. In particular, the Heizpfade can be Heizmäander. The heating paths may each comprise at least one heating conductor loop.

Vorzugsweise liegen die Temperaturen T₁, T₂ dabei in einem Temperaturbereich von 700 bis 900°C. Vorzugsweise kann die genannte Bedingung für alle Temperaturen T₁, T₂ innerhalb eines Betriebsbereichs gelten, beispielsweise dem genannten Bereich von 700 bis 900°C.To solve the problem described above, it is proposed to design the heating element in such a way that a total current provided via the contact elements is distributed in different ways to the heating paths at at least two different temperatures. In other words, the distribution of the total current to the Heizpfade should be temperature dependent. By way of example, the heating paths may comprise at least one first heating path and at least one second heating path, a first current I ₁ flowing through the first heating path and a second current I ₂ flowing through the second heating path, at least two temperatures T ₁ , T ₂ existing, with T ₂ > T ₁ , for which applies:

The temperatures T ₁ , T ₂ are preferably in a temperature range from 700 to 900 ° C. Preferably, said condition may apply to all temperatures T ₁ , T ₂ within an operating range, for example the said range of 700 to 900 ° C.

The heating paths, in particular the first heating path and the second heating path, may in particular be manufactured completely or partially from different materials and / or via different materials with the contact elements ( 120 ). This may in particular mean that the first heating path and / or a connection between at least one of the contact elements and the first heating path comprise at least one material which does not have the second heating path and / or a connection between at least one of the contact elements and the second heating path, and or that the second heating path and / or a connection between at least one of the contact elements and the second heating path comprise at least one material which does not have the first heating path and / or a connection between at least one of the contact elements and the first heating path. In particular, the different materials may have resistors with a different temperature behavior, that is to say materials with a different temperature dependence of their electrical resistances. For example, the first heating path may be made entirely or partially of a material having a first temperature behavior, whereas the second heating path is made wholly or partly with a material having a second temperature behavior or comprises such a material. In particular, the different materials may comprise at least one first material having a positive temperature coefficient (PTC material) and at least one second material having a negative temperature coefficient (NTC material). For example, at least one first heating path of the heating paths can consist of the at least one material with a positive temperature coefficient. For example, this can be done in such a way that the first heating path overall has a positive temperature behavior, so that a resistance of the first heating path decreases with increasing temperature, for example within a predetermined temperature range. At least one second heating path of the heating paths may comprise the at least one material having a negative temperature coefficient and / or be connected to one or more of the contact elements via the at least one material having the negative temperature coefficient. This at least one material with the negative temperature coefficient can for example form a section of the second heating path and / or a switching element, via which the second heating path is connected to one or more of the contact elements. Various embodiments will be described below in more detail by way of example.

The negative temperature coefficient material may particularly comprise a metal oxide. Preferably, the negative temperature coefficient material may be a metal oxide of any of the general formulas A _x1 B _x2 O _n and C _x3 D _x4 E _{x 5} O _m . In this case, A, B, C, D, E are each, preferably independently, metallic elements, wherein preferably A is La, where B is preferably is selected from the group consisting of Fe, Co, Ni and Cu, wherein C is preferably selected from the group consisting of La and Ba, wherein D is preferably selected from the group consisting of Ca and Sr and wherein E is preferably selected from Group consisting of Cr, Mn, Fe, and Co. x ₁ , x ₂ , x ₃ , x _4, and x ₅ are real numbers, and n and m are integers. In particular, the negative temperature coefficient material may be a material having a perovskite structure. or such a material, preferably a material of the general formula La _1-x Ca _x Cr _3-δ , where x is a real number greater than 0 and less than 1, preferably 0 <x <0.3, and where δ a real number 0 ≤ δ <1, preferably 0 <δ <0.3 and more preferably δ = 0.15.

If at least one material with a negative temperature coefficient is provided, this can be arranged in different ways. For example, a portion of the second heating path may be made entirely of such a material. Alternatively, the second heating path may also be made entirely of this material. Again, alternatively, at least one switching element may be provided, as described above, which for example consists entirely or partially of the material with a negative temperature coefficient, and which determines the current application and / or voltage application of the second heating path. In particular, at least one of the heating paths, for example the at least one second heating path, can be connected to at least one of the contact elements via at least one switching element. In particular, this switching element may comprise the material with the negative temperature coefficient or be made entirely of this material. For example, this switching element can be connected between the heating path, for example the second heating path, and the contact element. The switching element should be set up to effect a temperature-dependent distribution of the total current to the current paths.

As stated above, in a further aspect of the present invention, a sensor element is proposed for detecting at least one property of a gas in a measurement gas space, in particular for detecting a portion of a gas component in the gas. The sensor element has at least one heating element according to one or more of the embodiments described above or also below. The sensor element may in particular be a ceramic sensor element, preferably with a ceramic layer structure with one or more functional ceramics. In particular, the sensor element may comprise at least two electrodes, which are connected to one another via at least one solid electrolyte, for example a ceramic solid electrolyte material. In particular, at least one of the electrodes can be acted upon with gas from the measuring gas space. Various configurations of such sensor elements are basically known from the prior art. For example, the sensor element may be or comprise a so-called lambda probe for detecting an oxygen content in a gas. Alternatively or additionally, the sensor element may also comprise, for example, a NOx sensor or another type of sensor element.

• a) T < T_NTC: Bei geringer Betriebstemperatur sperrt der hochohmige NTC die elektrische Beschaltung der diesen NTC aufweisenden Heizpfade und/oder der über diesen NTC mit den Kontaktelementen verbundenen Heizpfade. Somit fließt lediglich durch den oder die nicht über den NTC mit Strom beaufschlagten Heizpfade ein Heizstrom. Der Widerstand des gesamten Heizelements ist damit vergleichsweise hoch. Dies erfüllt die oben beschriebenen Anforderungen seitens der Auslegung des Steuergeräts.
• b) T > T_NTC: Mit steigender Betriebstemperatur sinkt hingegen der Widerstand des NTCs, so dass zunehmend eine Strombeaufschlagung des über diesen NTC mit den Kontaktelementen verbundenen mindestens einen Heizpfads erfolgt, so dass ein zunehmender Heizstrom durch diesen mindestens einen zweiten Heizpfad fließen kann. Nun beteiligen sich mehrere Heizpfade am Heizprozess, und der Widerstand des gesamten Heizelements ist damit vergleichsweise klein. Dies erfüllt die zweite oben genannte Anforderung bezüglich der Begrenzung des Heizspannungsbedarfs.

The heating element and the sensor element according to one or more of the embodiments described above have numerous advantages over known heating elements and sensor elements. Thus, the heating element can be designed in particular as a self-regulating heating element. A self-regulation is preferably understood to mean a property in which the distribution of the currents onto the heating paths takes place independently and without external action, depending on the temperature prevailing at the location of the heating element. The heating element may in particular consist of several Heizmäandern. Depending on the operating temperature, the heating element may in particular be designed such that, depending on this operating temperature, a different number of heating paths participate in the heating process in different degrees. For example, the contacting of additional heating paths, for example one or more additional meanders, can be effected via a heat-conducting material, for example a material with a negative temperature coefficient (NTC), in order to ensure this different current distribution. Such negative temperature coefficient materials usually have a characteristic temperature T _NTC . In this case, the following applies for example for the following operating temperatures T of the heating element:

• a) T <T _NTC : When the operating temperature is low, the high-resistance NTC blocks the electrical wiring of the heating paths having these NTCs and / or the heating paths connected to the contact elements via this NTC. Thus, only by the or not energized via the NTC Heizpfade a heating current flows. The resistance of the entire heating element is thus comparatively high. This meets the requirements described above for the design of the control unit.
• b) T> T _NTC : With increasing operating temperature, however, the resistance of the NTC decreases, so that increasingly a current is applied to at least one Heizpfads connected via this NTC with the contact elements, so that an increasing heating current can flow through this at least one second heating path. Now participate in several Heizpfade am Heating process, and the resistance of the entire heating element is thus relatively small. This meets the second above-mentioned requirement regarding the limitation of the heating voltage requirement.

This results in several advantages. Due to the comparatively high total resistance of the heating element at low temperatures, an efficient design of a control device is possible, which can be connected to the sensor element and in particular to the heating element. On the other hand, due to the comparatively low total resistance of the heating element at high temperatures, the heating voltage requirement remains limited even with a high cooling of the entire sensor element and / or a high heating power requirement. Thus, the above-mentioned second condition is met in an excellent manner.

Furthermore, the concept described also offers many advantages in terms of usable materials. Thus, on the one hand, the known and proven heater system, for example based on platinum, can preferably continue to be used. Compared to a previous heater system according to the prior art, however, the use of the inventive design usually leads to a greatly reduced, effective temperature coefficient α.

Furthermore, the invention can also be used advantageously in terms of interconnection technology. As a rule, no additional heater line is needed, via which a wiring of the different Heizpfade can be realized. The multiple heating paths can be contacted via the same contact elements. Instead, the heating element preferably regulates autonomously and autonomously the distribution of the current to the heating paths. As a rule, no fundamental changes are required at the control unit.

In particular, the at least two heating paths can be connected in parallel, completely or partially electrically. By the parallel connection, in particular the parallel connection of a material with a positive temperature coefficient (PTC), in particular a platinum heater, and a material with a negative temperature coefficient, for example an NTC Heizpfads with at least one NTC material, preferably in a hot spot, the resulting total resistance of the heating element can be reduced. In general, for example, a heating voltage requirement, a FLO time (fast light-off, quick start of a lambda probe) and / or a use of precious metals can be reduced. Due to the parallel connection, for example the parallel connection of a platinum heater (PTC) and an NTC heater, for example in a meander supply region, the resulting temperature coefficient can be reduced during rapid heating. Overall, a heating element with a lower thermal stress can also be realized.

Further advantages arise with regard to the Rußleitpfade. Due to the generally higher temperature in the supply region, for example in the region of the contact elements and / or in the supply region of the heating paths, which extends for example close to a sealing packing of the sensor element, the formation of Rußleitpfaden to a housing, such as a probe housing, can be reduced.

Brief description of the drawings

Further optional details and features of the invention will become apparent from the following description of preferred embodiments.

Show it:

1 to 3 various embodiments of heating elements and sensor elements according to the invention;

4 a resistance profile of the heating element as a function of the operating temperature; and

5 a resistance behavior of typical perovskite materials for use as NTC materials in the context of the present invention.

Embodiments of the invention

In the 1 to 3 are various embodiments of inventive sensor elements 110 for detecting at least one property of a gas in a measuring gas space and various heating elements 112 represented according to the present invention. The entire sensor element 110 is doing in the 1 to 3 only schematically and partially indicated. For example, this may be a sensor element according to the prior art described above, for example a sensor element for detecting at least a portion of a gas component in a measurement gas space. The invention can generally be used preferably on motor vehicle sensors, for example sensors for detecting one or more gas fractions of one or more gas components in an exhaust gas of an internal combustion engine. For example, the invention can thus be used on lambda probes or on NOx sensors. Regarding a possible construction of the sensor elements 110 Apart from the construction of a heating element described below, reference may be made, for example, to the above-mentioned prior art.

The sensor element 110 comprises a ceramic layer structure, wherein in the 1 to 3 each plan views of a layer of the heating element 112 of the layer structure are shown. On this further layers may be constructed, which are not shown in the figures. The layer structure comprises, for example, one or more substrate materials 114 For example, ceramic substrate materials, for example zirconia-based, for example, yttrium-stabilized zirconia and / or scandium-doped zirconia. On these substrate materials 114 For example, one or more insulator materials may be used 116 be applied as a heater insulation, for example, Al ₂ O ₃ . On this insulator material 116 in turn, for example, this at least one insulator layer, then a heating resistor 118 of the heating element 112 be applied, for example by a printing process.

However, other production techniques are basically possible. The heating resistor 118 includes contact elements in the illustrated embodiments 120 , Which here by way of example and without limitation of other possible embodiments in each case two contact pads 122 and two leads 124 may include. Furthermore, the heating resistor comprises 118 in the illustrated embodiments, several heating paths, namely here a first example heating path 126 and a second heating path 128 , The first and the second heating path 126 respectively. 128 may also be referred to as first meander or second meander meander.

As described above, the heating element is configured such that one via the contact elements 120 Provided total current through the heating resistor 118 in a temperature-dependent manner on the at least two heating paths 126 . 128 is split. In general, the heating paths preferably have a different temperature behavior, wherein at least one of the heating paths 126 . 128 preferably has a temperature behavior with a positive temperature coefficient and at least one of the Heizpfade 126 . 128 preferably a temperature behavior with a negative temperature coefficient. In general, the admission preferably takes place in such a way that the proportion of the current through the heating path with a negative temperature coefficient increases with increasing temperatures.

In the in the 1 to 3 illustrated embodiments, this is realized in different ways. In 1 an embodiment is shown in which at least one switching element 130 can be provided. This switching element 130 can, for example, as in 1 shown between the second heating path 128 and one or both of the leads 124 be switched so that any current through the second heating path 128 flows, the switching element 130 must happen. This switching element 130 For example, a switching element may be made of a material having a negative temperature coefficient. Generally, therefore, the second heating path 128 comprise at least one NTC resistor and / or at least one NTC resistor with one or more of the contact elements 120 be connected. The NTC resistor 132 can basically at any point in the second heating path 128 be positioned. The position should preferably be selected according to a favorable transition temperature T _NTC . The NTC resistor 132 For example, by screen printing on a recess in the area between the supply line 124 and the second heating path 128 and / or in a recess within the second heating path 128 and / or printed over the entire area over and / or under the PTC heating path. Basically suitable materials with a negative temperature coefficient all ceramic, co-sinterable NTC materials into consideration. Other requirements are usually chemical compatibility with the materials used in the heater network and one with the other materials of the heating resistor 118 comparable oxidation stability, for example, comparable to platinum oxidation stability. As will be explained in more detail below, in particular the use of perovskites, such as (La, Ca) CrO ₃ , is promising.

Alternatively or in addition to the use of a switching element 130 , Preferably, a switching element with a negative temperature coefficient, the first heating path 126 and the second heating path 128 can also be connected to each other over a large area and / or one or more of the heating paths can be made entirely of different materials. While, for example, in 1 the second heating path 128 not completely made of the material with a negative temperature coefficient (this may nevertheless be) are in the 2 and 3 various embodiments shown in which the second heating path 128 preferably made entirely of a material having a negative temperature coefficient and thus practically completely an NTC resistor 132 forms. Also in this case, the resistance properties with a negative temperature coefficient, analogous to 1 , a temperature-dependent distribution of the total current, and thus a circuit property.

In the embodiment according to 2 a layer structure is shown in which the Heizpfade 126 . 128 lie large area on each other and thus a large area, are connected in parallel. For example, first, as in 2 shown, the second heating path 128 on the insulator material 116 applied, for example, be printed, which can preferably be configured over a large area. On this can then, preferably designed narrower, the first heating path 126 applied, for example, be printed, for example, in a. Step with the production of the supply lines 126 , The second heating path 128 thus becomes a large area of the first heating path 126 contacted. This also makes it possible, for example, by overprinting of NTC material by platinum, a large parallel connection can be achieved. Preferably, a transition 134 between the supply lines 124 and the heating paths 126 . 128 be designed large area, so that a large, heatable transition between the Heizpfaden 126 . 128 and the range of supply lines 124 arises. Overall, can be achieved by the described structure a maximum saving of precious metals, such as a board savings. Furthermore, it is possible to integrate the supply lines 124 , realize a low total resistance in the high temperature range. The transition 134 can be close to a (not shown) sealing packing of the sensor element 110 introduce. Due to the high temperature so Rußleitpfade can be avoided up to an optional sealing packing, and there is a total of a lower temperature gradient in the supply of Heizpfade 126 . 128 ,

In 3 an alternative embodiment is shown in which the first heating path 126 which is preferably made entirely of a material having a positive temperature coefficient, for example platinum, and the second heating path 128 with the NTC resistor 132 , laterally offset from each other and preferably, outside the transition region 134 , are electrically isolated from each other. This structure can also be produced for example by overprinting, for example by the Heizpfade 126 . 128 sequentially on the insulator material 116 be imprinted so that these are in the area of transition 134 through the supply lines 124 are contacted. The first heating path 126 , which in turn may be configured as a PTC heater, and the narrow NTC resistor 132 can be designed such that a heat transfer between these Heizpfaden 126 . 128 with a distance-dependent time constant. As a result, the temporal effectiveness of the parallel circuit can be controlled and influence on a control characteristic and / or control stability of heat-voltage controlled applications without an internal resistance control can be taken.

In 4 is an example of a schematic course of the resistances of the entire heating resistor 118 represented, divided into the heating resistor of the first Heizpfads 126 and the second heating path 128 , Here, R _H denotes the total resistance of the heating resistor 118 , R _{H, h} the total resistance at high temperatures, and R _{H, k} the total resistance at low temperatures. R _{H, 1} and R _{H, 2} and R _{H, g} denote the resistances of the first heating path 126 or the second Heizpfads 128 or the composite total heating resistor 118 , From this schematic course it follows that a reduction can be achieved by about 50%, for example, if the two Heizpfade 126 . 128 are designed in the same length and with the same cable cross-section.

As shown above, the different distribution of currents I ₁ through the first heating path 126 and I ₂ through the second heating path 128 , which is temperature dependent, in particular by the use of a material with a negative temperature coefficient achieve. This material, preferably as an NTC resistor 132 in the second heating path 128 can be used, for example, (La, Ca) CrO ₃ include. The perovskite material of the abovementioned general formulas A _x1 B _x2 O _n or C _x3 D _x4 E _x5 O _m (frequently also represented in the literature as general formula ABO ₃ ), in particular (La, Ca) CrO ₃ , is used as the material used in fuel cells and is there exposed to both reducing and oxidizing gases. The temperature behavior of its conductivity σ is in 5 shown, wherein the conductivity σ is plotted logarithmically over the inverse of the temperature T. The measurements are I. Yasuda, T. Hikita, Electrical conductivity and defect structure of calcium doped lanthanum chromites. J. Electrochem. Soc. 140 (6), 1699-1704 (1993) taken. The measurements are carried out in air. For example, for the uppermost curve shown, there is a hot resistance Rh of 2 Ω, and a cold resistance R _k of 12 Ω. Alternatively, or in addition to the perovskite-type (La, Ca) _CrO3 can also be used YCrO _3, for example, also as representative of the preferred materials of the type ABO. ₃ However, materials of the type (La, Ca) CrO ₃ generally have numerous advantages. For example, they are co-sinterable to other layer materials of typical sensor elements 110 , The material can furthermore be applied by paste and / or screen printing, so that conventional work-up and / or processing can be carried out in accordance with conventional metal oxides. Furthermore, this material is chemically compatible with the other materials, which are typically in sensor elements 110 used, compatible, for example, compatible with conventional substrate materials 114 such as yttrium-stabilized zirconia. Furthermore, these materials have high cold resistance and low hot resistance. For an assumed geometry of the switching element 130 with a length of 50 microns, a width of 200 microns and a height of 20 microns, for example, results in a cold resistance at a temperature of 25 ° C of about 12 Ω and a hot resistor at a temperature of 723 ° C of 2 Ω, such as also in 5 indicated. Furthermore, the Resistance of this perovskite material over a wide range (for example 10 ^-10 bar and 1 bar) also independent of an oxygen partial pressure, resulting in sensor elements 110 is particularly advantageous for detecting oxygen partial pressures.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2007/062969 A1 [0003]
• WO 2001/044798 A1 [0003]

Cited non-patent literature

• Robert Bosch GmbH: Sensors in the motor vehicle, edition 2007, pages 154-159 [0001]
• I. Yasuda, T. Hikita, Electrical conductivity and defect structure of calcium doped lanthanum chromites. J. Electrochem. Soc. 140 (6), 1699-1704 (1993) [0031]

Claims (10)

Heating element ( 112 ), in particular for use in a sensor element ( 110 ) for detecting at least one property of a gas in a measurement gas space, comprising at least two contact elements ( 120 ) and at least two via the contact elements ( 120 ) Heizspade acted upon by heating current ( 126 . 128 ), wherein the heating element ( 112 ) is configured such that a via the contact elements ( 120 ) provided at least two different temperatures in different ways on the Heizpfade ( 126 . 128 ) is divided. Heating element ( 112 ) according to the preceding claim, wherein the heating paths ( 126 . 128 ) at least one first heating path ( 126 ) and at least one second heating path ( 128 ), wherein through the first heating path ( 126 ) flows through a first current I ₁ and wherein by the second heating path ( 128 ) a second stream 12 flows, wherein at least two temperatures T ₁ , T ₂ exist with T ₂ > T ₁ , for which applies:

Heating element ( 112 ) according to one of the preceding claims, wherein the heating paths ( 126 . 128 ), in particular the first heating path ( 126 ) and the second heating path ( 128 ) are made wholly or partly from different materials and / or via different materials with the contact elements ( 120 ) are connected. Heating element ( 112 ) according to the preceding claim, wherein the different materials have resistors with a different temperature behavior. Heating element ( 112 ) according to one of the two preceding claims, wherein the different materials have at least one first material with a positive temperature coefficient and at least one second material with a negative temperature coefficient. Heating element ( 112 ) according to one of the three preceding claims, wherein at least one first heating path ( 126 ) of the heating paths ( 126 . 128 ) consists of at least one material with a positive temperature coefficient, at least one second heating path ( 128 ) of the heating paths ( 126 . 128 ) has at least one material with a negative temperature coefficient and / or on the at least one material with the negative temperature coefficient with one or more of the contact elements 120 connected is. Heating element ( 112 ) according to one of the two preceding claims, wherein the material having the negative temperature coefficient comprises a metal oxide, preferably a metal oxide according to one of the formulas selected from: A _x1 B _x2 O _n and C _x3 D _x4 E _x5 O _m , where A, B, C, D, E are each metallic elements, preferably A is La, wherein B is preferably selected from the group consisting of Fe, Co, Ni and Cu, wherein C is preferably selected from the group consisting of La and Ba, wherein D is preferably selected from the group consisting of Ca and Sr and wherein E is preferably selected from the group consisting of Cr, Mn, Fe, and Co, where x ₁ , x ₂ , x ₃ , x ₄ and x _{5 are} real numbers and where n and m are integers. Heating element ( 112 ) according to one of the four preceding claims, wherein the material having the negative temperature coefficient comprises a material having a perovskite structure, preferably a material selected from the group consisting of: a material of the general formula La _1-x Ca _x CrO _{3 -δ} , where x is a real number greater than 0 and less than 1, preferably 0 <x <0.3, and where δ is a real number 0 ≤ δ <1, preferably 0 <δ <0.3, and more preferably δ = 0.15. Heating element ( 112 ) according to one of the preceding claims, wherein at least one of the heating paths ( 126 . 128 ) with at least one of the contact elements ( 120 ) via at least one switching element ( 130 ), in particular a switching element ( 130 ) having a negative temperature coefficient, wherein the switching element ( 130 ) is arranged to provide a temperature-dependent distribution of the total current to the heating paths ( 126 . 128 ) to effect. Sensor element ( 110 ) for detecting at least one property of a gas in a measurement gas space, in particular for detecting a proportion of a gas component in the gas, wherein the sensor element ( 110 ) at least one heating element ( 112 ) according to one of the preceding claims.

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