Thermoelectric switching element, use of a thermoelectric switching element, and method for producing a thermoelectric switching element

Abstract

The invention relates to a thermoelectric switching element (2) having a first layer (4) that consists at least in part of a ferromagnetic material and having a second layer (6) that consists at least in part of a metal material, wherein: the ferromagnetic material of the first layer (4) and the metal material of the second layer (6) have different coefficients of thermal expansion; the coefficient of thermal expansion of the ferromagnetic material of the first layer (4) and the coefficient of thermal expansion of the metal material of the second layer (6) are selected and the first layer (4) and the second layer (6) are interconnected and arranged relative to one another in such a way that a specified deformation of the composite of the first layer (4) and the second layer (6) occurs when a specified temperature is reached; and the first layer (4) and the second layer (6) are interconnected by an adhesive bond (10) with atomic diffusion (12), optionally via an intermediate layer (22). The invention also relates to the use of a thermoelectric switching element (2) and to a method for producing a thermoelectric switching element (2).

Description

[0001]December 12, 2024 Thermoelectric switching element, use of a thermoelectric switching element, and method for producing a thermoelectric switching element. The invention relates to a thermoelectric switching element with at least two layers, as well as to the use of a thermoelectric switching element and a method for producing a thermoelectric switching element. Thermoelectric switching elements of the type of interest here can be used for various purposes and are used in particular as switching elements, for example as switches or parts of a switch, in devices or systems, especially in electronic devices or systems.Furthermore, the aforementioned thermoelectric switches are used in the fields of electrical engineering, electronics, smart devices, cookware such as cookware or cooking utensils such as pots, pans, baking sheets, pizza stones, or other devices with or in which food can be heated or cooked, white goods such as large household appliances such as electric stoves, refrigerators, freezers, washing machines, dryers, or dishwashers, energy storage devices, fuel cells, electrolyzers, batteries and battery management systems, and energy converters. Furthermore, the aforementioned thermoelectric switches are used in the field of water extraction, particularly through seawater desalination, and in the field of geothermal energy. In particular, a process can be triggered by means of the thermoelectric switching elements based on thermal and / or electrical, for example, thermoelectric, effects.For example, an electrical circuit can be closed or opened. In particular, the thermoelectric switching element makes it possible to use an electrical voltage to generate a temperature difference or to use a temperature difference to generate an electrical voltage. Applications as an element of a circuit breaker or as overheating protection are conceivable, for example. The aforementioned thermoelectric switching elements could also be used as electromechanical components or parts. For example, a mechanical process can be triggered by applying an electrical voltage, or an electrical voltage can be induced by triggering a mechanical process.Thermoelectric switching elements can be used, for example, in devices that heat various materials in the broadest sense or can control a heating process, as well as in applications with switching mechanisms, particularly in connection with heating processes. In these areas, fundamentally different requirements are placed on the material properties of a thermoelectric switching element. In particular, the required properties depend on the prevailing or targeted temperatures in the respective application. When the thermoelectric switching element is used in connection with heating processes, the required material properties depend in particular on the specific heating process, the materials to be heated, or the respective switching mechanism.Furthermore, thermoelectric switching elements are often constructed from different materials, for example from different layers of different materials. In general, by combining two or more layers, in particular layers comprising different metallic materials, the material-specific properties of the layers can be advantageously combined. However, it must be noted that the combination can influence the properties of the component resulting from the combination. For components that have several, i.e. two or more, in particular different, layers and which have an electromagnetic and / or electromechanical function, for example when used as a thermoelectric switching element, the quality of the combination of the two or more layers is crucial. Of importance here is RO / sw 230689WO 12.December 2024 that the composite does not significantly negatively impact the electromagnetic and / or electromechanical properties of the component. For example, there should be no significant negative impact in the sense that energy is lost due to inhomogeneities at the transition between different materials and / or layers, and / or that the electromagnetic or electromechanical properties deviate significantly from the desired properties. For example, thermoelectric switching elements are known from the prior art which have, in particular, different, metallic layers and in which an effect or switching mechanism is based on the, in particular, different, electromagnetic and / or electromechanical properties of the metallic materials of the layers. Examples of such effects include the Seebeck effect, the Peltier effect, or the Thomson effect.To utilize these effects, for example, to cool sensitive electronic components, it is crucial that the materials used do not deviate, or only deviate insignificantly, from their predicted behavior. The composite of two metallic materials with different thermal expansion coefficients is known as a bimetal or thermal bimetal. The composite usually takes the form of two superimposed layers in a metal strip. When a predetermined temperature is reached, especially as the temperature increases, one of the two layers of the metal strip expands more than the other due to the different thermal expansion coefficients, causing the strip to bend toward the layer with the lower thermal expansion coefficient.Materials used include iron (Fe), nickel (Ni), or steel, as well as alloys with these materials or combinations of these materials. This effect can be used as a switching mechanism, for example for temperature control. One possible use is a predetermined deformation of the layers at a predetermined temperature that closes an electrical circuit and thus generates an electrical switching signal. This can be used, for example, to switch a heating process on or off or to indicate that a predetermined temperature has been reached. Furthermore, the composite of layers, in particular those arranged next to one another, is known from the prior art.At least one layer consists of a high-resistance material (resistance material) and at least one further layer, usually two further layers, consists of a material that is more electrically conductive than the resistance material (conductor material). This composite is known as a shunt resistor. The layers of conduction material usually serve to make contact and are preferably arranged on the outside of the shunt resistor. For this purpose, the conduction material surrounds the resistance material on at least two sides. A shunt resistor is usually connected in parallel to part of an electrical circuit in order to divert an electrical current from this part. A shunt resistor can also be connected in parallel to an ammeter in order to expand the measuring range of the ammeter. This can increase the current that can be directly measured by the ammeter.The measured current can also be used as an electronic switching signal. A shunt can also be used as a current measuring resistor, usually as a low-ohm electrical measuring resistor. This usually small precision resistor is integrated, for example, into a current path. By measuring the voltage drop across the measuring resistor, which is proportional to the current flowing through the measuring resistor, the current can be calculated if the value of the measuring resistor is known. This application is particularly relevant for precise current measurement in power supplies, battery management systems, and drives. The advantage here is that shunts can generally be manufactured cost-effectively, and at the same time, through targeted resistor selection, they enable precise current measurement and thus, among other things, precise switching based on a current measurement.The precisely defined resistance value of the shunt should not be influenced in an unpredictable manner by the composite of the materials, in particular by any resulting inhomogeneities in the composite. Furthermore, in thermoelectric switching elements known from the prior art with at least two interconnected layers, the service life of the thermoelectric switches may be limited by the composite. This is because the thermoelectric switch represents a potential material weakness due, for example, to existing inhomogeneities or additional (adhesive) layers. Furthermore, the use of ferromagnetic materials is known from the prior art.In general, ferromagnetic materials completely lose their ferromagnetic properties when their specific Curie temperature (Tc) is reached, so that above this temperature the materials are only paramagnetic. Below this temperature, which marks the reversible phase transition of ferromagnetic materials into their high-temperature paramagnetic form, the materials regain their ferromagnetic properties. This effect is used, for example, for temperature control in thermostats or in data storage using magneto-optical media and can thus also be used as a switching mechanism.Against this background, the present invention is based on the technical problem of specifying a thermoelectric switching element and a method for producing a thermoelectric switching element that improve the disadvantages described for the prior art and, in particular, exhibit high quality with a long service life. The aforementioned technical problem is solved according to a first teaching of the invention in a thermoelectric switching element with a first layer consisting at least partially of a ferromagnetic material and with a second RO / sw 230689WO 12.December 2024 Layer at least partially consisting of a metallic material, wherein the ferromagnetic material of the first layer and the metallic material of the second layer have different thermal expansion coefficients, and wherein the thermal expansion coefficient of the ferromagnetic material of the first layer and the thermal expansion coefficient of the metallic material of the second layer are selected and the first layer and the second layer are connected to one another and arranged relative to one another in such a way that when a predetermined temperature is reached, a predetermined deformation of the composite of the first layer and the second layer is achieved, solved in that the first layer and the second layer are connected to one another by an adhesive bond with atomic diffusion, optionally via an intermediate layer.The thermal expansion coefficient of the ferromagnetic material of the first layer and the thermal expansion coefficient of the metallic material of the second layer are selected, and the first layer and the second layer are connected and arranged relative to one another in such a way that, upon reaching a predetermined temperature, a predetermined deformation of the composite of the first layer and the second layer is achieved. This is understood, in particular, to mean that the first layer and the second layer are connected to one another, wherein the thermal expansion coefficient of the ferromagnetic material of the first layer and the thermal expansion coefficient of the metallic material of the second layer are different, wherein the composite of the first layer and the second layer exhibits a predetermined deformation upon reaching a predetermined temperature.In particular, for the existence of different thermal expansion coefficients, it is sufficient if the thermal expansion coefficients only have a minimal difference, for example only by about 0.1*10. -6 K -1In particular, different thermal expansion coefficients can be achieved by the targeted selection of the materials of the first and second layers. RO / sw 230689WO December 12, 2024 According to a second teaching of the invention, the above-mentioned technical problem is further solved in a thermoelectric switching element, with a first layer at least partially consisting of a ferromagnetic material, and with a further layer which has at least: a resistance region at least partially consisting of a metallic material, and two conducting regions which at least partially consist of a metallic material different from the metallic material of the resistance region, wherein the conducting regions are each arranged adjacent to different sides of the resistance region and are connected to the resistance region, in that the first layer and the further layer are connected by an adhesive bond withatomic diffusion, optionally via an intermediate layer. In particular, a high-resistance resistance alloy can be provided as the metallic material of the resistance region, for example a nickel-chromium-based, copper-nickel-based, or iron-nickel-based alloy. The material of the conductive regions can, in particular, be a material consisting at least partially of copper or aluminum. The further layer can have a thickness of 10 mm or less, preferably 8 mm or less. Within the scope of the invention, it was recognized that a bond between two metallic layers of a thermoelectric switching element can be reliably achieved by an adhesive bond with diffusion. In this way, a thermoelectric switching element with improved material properties, in particular with improved electromagnetic and / or electromechanical properties, can be provided. Such a bondFor example, internal stresses at the junction of the bonding partners involved and thus within the thermoelectric switching element can be reduced. Inhomogeneities in the composite can also be reduced or even avoided through the gradual diffusive transition of the materials of the connected layers. RO / sw 230689WO December 12, 2024 Furthermore, the thermoelectric switching element according to the invention can achieve a long service life with consistently high quality, since the bond can be achieved without the addition of adhesive or filler layers. The first and second layers or the further layer can be directly bonded to one another by adhesive bonding with atomic diffusion or optionally bonded to one another via an intermediate layer. The intermediate layer can be electrically insulating; for example, the intermediate layer can be made at least partially, preferably substantially, of non-metals, metal oxides, ceramics, or plastic.Alternatively, the intermediate layer can also be electrically conductive, so that the electrical properties of the thermoelectric switch can be specifically influenced by means of the intermediate layer. By means of the thermoelectric switching element, the service life of the parts and components for or in which the thermoelectric switching element is used can also be increased. Furthermore, the thermoelectric switching element is easily recyclable, in particular since it preferably only comprises purely metallic materials. Furthermore, by providing the first layer at least partially consisting of a ferromagnetic material, a switching mechanism based on the property of a ferromagnetic material to exhibit a reversible phase transition at the Curie temperature Tc can advantageously be combined with further switching mechanisms or thermoelectric properties of the thermoelectric switching element by means of the second orthe further layer. For example, it is possible to expand the switching mechanism based on the different thermal expansion coefficients of the first and second layers (thermobimetal effect) by a switching mechanism acting as overheating protection through the ferromagnetic material of the first layer. Preferably, the thermal expansion coefficients of the ferromagnetic material of the first layer and the metallic material of the second layer are selected such that a predetermined temperature greater than or equal to 37°C leads to a predetermined deformation of the composite of the first layer and the second layer. In particular, the thermoelectric switching element is further configured such that a predetermined deformation leads to the triggering of a switching mechanism, for example by opening or closing a circuit, in particular by establishing a conductive contact through the deformation or bythe loss of a conductive contact due to the deformation. In particular, the ferromagnetic material of the first layer can have a Curie temperature Tc, below which heating should occur and above which heating should be switched off. The electrothermal switching element can be configured such that when the Curie temperature Tc of the ferromagnetic material of the first layer is reached, a switching mechanism is triggered which interrupts or switches off a heating process. For example, the reversible phase transition of the ferromagnetic material at Tc can be detected by measuring the specific material properties of the first layer, which at least partially consists of the ferromagnetic material, for example the specific resistance, and thus switching can be triggered. In particular, a sensor or a measuring element can be provided on the switching element or connected to it. The effect of the change of the ferromagneticMaterial to a paramagnetic material can be used directly as a switching mechanism, for example, by opening a previously closed magnetic circuit due to the loss of magnetism of the previously ferromagnetic material upon reaching Tc. In addition, further advantageous material properties can be introduced into the electrothermal switching element by the material of the second or further layer and used as a switching effect. If the material of the second or further layer is also ferromagnetic, it can be provided that the material of the second or further layer has a Curie temperature Tc that is above the Curie temperature Tc of the material of the first layer. RO / sw 230689WO December 12, 2024 In particular, by means of the thermoelectric switch according to the invention, a switching mechanism based on the reversible phase transition at the Curie temperature Tc can be combined with a switching mechanism based ondifferent thermal expansion coefficients (thermobimetal) and / or with current measurement by means of a shunt resistor. In addition to the aforementioned layers, the first layer, the second layer or the further layer, as well as the optional intermediate layer, at least one additional layer made of a ferromagnetic and / or metallic material or another material, such as plastic or graphene, can be provided. This allows further advantageous properties to be introduced into the composite. The at least one additional layer can have a thermal expansion coefficient that differs from the existing layers. Preferably, the at least one additional layer is also introduced into the composite by means of an adhesive bond with atomic diffusion. Alternatively, the at least one additional layer can be present as a layer that is not introduced into the composite by means of an adhesive bond with atomic diffusion.is, for example, an adhesive layer that adheres by means of an adhesive. In the present case, a bond through an adhesive bond with atomic diffusion is understood to be a bond between two bonding partners in which a transition layer forms as a bonding zone through atomic diffusion of the materials of the bonding partners, via which a continuous adaptation of the material properties takes place. The adhesive bond with atomic diffusion is thus created by the formation of the transition layer between the layers. In the transition layer, the atoms of the bonding partners are gradually mixed; the formation of a bond occurs through exchange processes (diffusion) in the transition layer, also called the bonding zone. This transition layer causes the reduction of internal stresses. The extent of the transition zone depends on the bonding partners used, in particular the diffusion properties of theMaterials involved. To characterize the adhesive bond with atomic diffusion in the bonding zone and its properties, analyses can be carried out using various methods. These methods include optical light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), secondary ion mass spectrometry (SIMS), and analyses of microhardness profiles. Such a composite can be referred to, for example, as a cladding composite. Preferably, the two bonding partners are metallic materials, and the cladding composite represents a metallic connection of the two or more bonding partners or cladding partners. In particular, the bonding partners of the composite are arranged in layers adjacent to one another. The bonding partners in the cladding composite can be connected by means of cladding. For this purpose, cladding can be carried out by cold roll cladding or hot cladding.The bonding partners can alternatively be connected by welding metal strips, in particular diffusion welding or electric welding, or by stacking and partial welding. Furthermore, production by sintering or by hot isostatic pressing (HIP) as well as by 3D printing is possible. The aim and, in this respect, the preferred design of the layers is to form continuous layers in order to best achieve the desired properties of each layer. However, the layers can also be formed as discontinuous layers, since the continuity of the layers cannot be fully guaranteed during production. On the other hand, depending on the materials used, the production of a discontinuous layer can also be desired, so that the material of one layer can penetrate the material of another layer. RO / sw 230689WO December 12, 2024 In this way,Further properties of the composite, such as conductivity or durability, can be improved. The material of one layer can also contain further components and inclusions. The materials of the first layer and the second or further layer can essentially consist of a metal or be a metallic alloy. The term "essentially consisting of" is understood to mean that, in addition to the specified material, the material can contain unavoidable impurities, such as small amounts of oxygen (O) or carbon (C). In particular, it is preferred that the specified material, in particular the metallic material, has a high degree of purity, for example a purity of at least 99.9%, preferably of at least 99.95%, and particularly preferably of 99.99%. In particular, the thermoelectric switching element is designed as a flat composite part, i.e., the at least two layers are adjacent to one another.arranged, optionally by means of an intermediate layer, for example, the two layers, and optionally the intermediate layer, are arranged one above the other in the form of a stack. The bonding zone as a transition layer is preferably formed at the interface between the at least two layers, optionally at the interface between a layer and the intermediate layer. In general, the transition layer, in which the adhesive bond has been created by atomic diffusion, can have several contiguous or non-contiguous regions. The transition layer can also be homogeneous, for example of constant thickness, or inhomogeneous, for example with a greater thickness in certain sections. In this way, a thermoelectric switching element with different properties in certain sections can be achieved by means of the transition layer. The thermoelectric switching element can have a rectangular shape. The production of this comparatively simple shape is uncomplicated andtherefore RO / sw 230689WO December 12, 2024 cost-effective. However, other shapes for the thermoelectric switching element are also possible. For example, the thermoelectric switching element can have the shape of a distance compensation element, which is also called a gap filler. A distance compensation element serves for the secure arrangement of components with varying dimensions in component groups and is arranged between these components. For example, the thermoelectric switching element, in particular for use as a distance compensation element, can be designed as a metal foil with integrally formed spring elements. The spring elements protrude from the plane of the metal foil and are in contact with at least one of the two components between which the distance compensation element is arranged. Furthermore, the thermoelectric switching element can be in the shape of a worm or spiral, ie for example as a metal foil which is rolled up in a worm shapeThis shape is advantageous, for example, when using the thermoelectric switching element in a thermometer, in particular for temperature display by means of the deformation of the thermoelectric switching element due to the different thermal expansion coefficients of the materials of the first layer and the second layer of the thermoelectric switching element. Furthermore, the thermoelectric switching element can also be designed in the form of a snap disc (SnapDisc), for example as a flat metal foil with a spherical cap-shaped curved area. In particular, the layers of the thermoelectric switching element can be designed and arranged in such a way that the curvature of the spherical cap-shaped curved area changes under the influence of temperature, in particular in the opposite direction. This change in the curvature can advantageously be used as a switching mechanism. The snap disc can also be formed by amechanical action, for example in the form of a mechanical actuation by exerting pressure on the curvature, can be used as a switch. The technical problem outlined above is also solved according to a further teaching by the use of a thermoelectric switching element RO / sw 230689WO December 12, 2024 as overheating protection, in particular in a cooking utensil or an electronic circuit, wherein the thermoelectric switching element is designed according to one of the previously explained examples and variants. In particular, use as overheating protection of the thermoelectric switching element is understood to mean that it is designed such that when a predetermined temperature is reached, a switching mechanism is triggered, which causes the switching off of a heating mechanism or a current flow and thus prevents overheating. The switching mechanism can, for example, be triggered when the Curie temperature Tc is reached as a result ofchanged electrical or magnetic properties of a material of a layer and / or by thermal expansion of a material of a layer and / or by temperature-dependent electrical properties, for example the specific resistance, of a material of a layer. In general, the use of the specified thermoelectric switching element or an embodiment thereof is preferred in the fields of electrical engineering, electronics, smart devices, cookware, such as cookware or cooking utensils such as pots, pans, trays, pizza stones or other devices with or in which food can be heated or cooked, white goods, such as large household appliances such as electric stoves, refrigerators, freezers, washing machines, dryers or dishwashers, energy storage devices, fuel cells, electrolyzers, batteries and battery management systems as well as energy converters. A cookware can also be an oven or a stove or a part thereof. The cookware can also bea device by means of which substances are warmed, heated, or processed outside the home kitchen. Furthermore, the thermoelectric switching element or an embodiment can also be used in a device for evaporation, for example for the evaporation of liquid. For example, it can be a device for drinking water production, by means of which seawater is evaporated and thus can be desalinated. Other condensation applications for other liquids are also conceivable. Furthermore, uses in the field of geothermal energy are also conceivable, wherein the natural thermal energy from the interior of the earth can be used, in particular for heating substances and liquids such as (sea)water. The above-mentioned technical problem is also solved according to the invention by a method for producing a thermoelectric switching element, in particular the previously described thermoelectricSwitching element or an embodiment thereof, in which a first layer is provided which consists at least partially of a ferromagnetic material, in which a second layer is provided which consists at least partially of a metallic material, in which an intermediate layer is optionally provided, in which the first layer and the second layer are arranged adjacent to one another, optionally by means of the intermediate layer arranged between the first layer and the second layer, and in which an adhesive bond with atomic diffusion is created between the first layer and the second layer, optionally in each case by means of the creation of an adhesive bond with atomic diffusion between the first layer and the intermediate layer and between the second layer and the intermediate layer. The method enables an individual composite structure from layers of different materials as well as a variation of the layer thicknesses of the individual layers with high adhesive strength of the layers.among themselves. In particular, the layers are bonded together to form a composite material. Overall, this enables a targeted adaptation of the properties of a thermoelectric switching element to various applications. Furthermore, the thermoelectric properties of the thermoelectric switching element can be influenced and specifically adapted to different applications and, in particular, to different temperatures at which a switching process is to be triggered, particularly through targeted material selection of the layers. Furthermore, the selection of materials with different RO / sw 230689WO December 12, 2024 thermal expansion coefficients can positively influence the so-called interaction between the layers and the resulting stresses. The above-mentioned process also allows a variation of the layer thicknesses of the individual layers, so that the desired properties of the thermoelectric switching elementcan be further influenced in a targeted manner. The first layer that is provided consists at least partially, preferably completely, of a ferromagnetic material. More preferably, the second layer consists at least partially, preferably completely, of a metallic material, in particular of a metallic material that differs from the ferromagnetic material of the first layer. Optionally, an intermediate layer is provided and optionally, the first layer and the second layer are arranged adjacent to one another by means of the intermediate layer arranged between the first layer and the second layer. In this case, the adhesive bond between the first layer and the second layer is created by creating an adhesive bond with atomic diffusion between the first layer and the intermediate layer and between the second layer and the intermediate layer. This means that a transition layer with atomic diffusion is formed both between the first layer andthe intermediate layer as well as between the second layer and the intermediate layer in the case of an intermediate layer being present. Preferably, the first layer and the second layer are arranged on opposite sides of the intermediate layer. If no intermediate layer is provided, the adhesive bond is created by atomic diffusion, in particular directly, between the first layer and the second layer, so that a diffusion of atoms of the material of the first layer into the second layer and of atoms of the material of the second layer into the first layer takes place. Furthermore, the transition layer can be provided and correspondingly designed such that the (atomic) diffusion between the first layer and the second layer extends over the intermediate layer. Accordingly, the transition layer can be designed such that atoms of the first layer diffuse via the intermediate layer into the second layer and atoms of the second layer via theintermediate layer into the first layer. In this way, the properties caused by the transition layer are enhanced, for example, the bond between the layers can be further strengthened. The optional intermediate layer can be designed to be electrically insulating, for example as a plastic layer, or electrically conductive, for example at least partially consisting of a metal, such as copper (Cu). In particular, the method can provide for the ferromagnetic material of the first layer and the metallic material of the second layer to have different thermal expansion coefficients, wherein the thermal expansion coefficients of the ferromagnetic material of the first layer and the metallic material of the second layer are selected in such a way, and the first layer and the second layer are arranged in such a way relative to one another that, upon reaching a predetermined temperature, a predetermined deformation of the bond between the first layer and thesecond layer, which optionally includes the intermediate layer. In the above-mentioned method, the respective bonding partners, in this case the first and second layers and optionally the intermediate layer, are arranged adjacent to one another and brought into intimate contact, in particular brought closer to atomic distances. The superimposing of the layers can be preceded by a cleaning process in which the contacting surfaces are freed, for example, from absorbed gases, oxide layers or contaminants such as oil residues. The cleaning process and in particular the removal of the oxide layers increases the bonding capacity of the surfaces of the bonding partners. The oxide layers and generally the surface layers of the bonding partners can also be broken up or roughened by further processes, for example RO / sw 230689WO December 12, 2024 forming processes, to increase the surface reactivity. Other processes such asRolling or stretching is used to solidify near-surface regions of the bonding partners and to create highly active surfaces. According to a further teaching of the invention, the above-mentioned technical problem is also solved by the use of a thermoelectric switching element in a cookware, wherein the thermoelectric switching element comprises: a first layer at least partially consisting of a ferromagnetic material, and a second layer at least partially consisting of a metallic material, wherein the first layer and the second layer are connected to one another by an adhesive bond with atomic diffusion, optionally via an intermediate layer. In particular, the metallic material of the second layer differs from the ferromagnetic material of the first layer. For example, the metallic material of the second layer and the ferromagnetic material of the first layer can have different thermal expansion coefficients.In particular, the ferromagnetic material of the first layer comprises nickel (Ni) or a nickel alloy. In this way, the latter thermoelectric switching element can ensure that a certain temperature, in particular a temperature above the Curie temperature Tc, is not exceeded during a cooking process, so that food prepared using the cookware or other materials to be heated are not heated to too high a temperature. A cookware can, for example, be cookware or other cooking utensils such as pots, pans, trays, pizza stones or other devices with or in which food or other materials such as drinking water can be heated or cooked. A cookware can also be an oven or a stove or a part thereof. The cookware can also be a device by means of which materials are warmed, heated or processed outside the home kitchen. Furthermore, the latter thermoelectricThe switching element can also be used in a device for evaporation, for example for the evaporation of liquids. This can, for example, be a device for producing drinking water, by means of which seawater can be evaporated and thus desalinated. Other condensation applications for other liquids are also conceivable. Preferably, the use of the last-mentioned thermoelectric switching element in a cookware, for example a cookware with a built-in thermoelectric switching element, ensures that the maximum temperature achievable by the cookware can be regulated, for example within the framework of inductive heating. If the Curie temperature Tc of the ferromagnetic material of the thermoelectric switching element is reached, it loses its ferromagnetic properties and the inductive heating stops. Due to the characteristic Curie temperature Tc of the thermoelectric switching element,Thus, a maximum heating temperature can be selected, whereby if this temperature is exceeded, the inductive heating can be stopped by the reversible phase transition of the ferromagnetic material. In this way, the thermoelectric switch can be used in a cookware for heating temperature-sensitive materials. For example, the maximum temperature can be limited by the cookware, especially when nickel (Ni) or a nickel alloy is used as the ferromagnetic material of the first layer, to temperatures of 360 °C or below, so that the preparation of food can be optimized using the cookware with a thermoelectric switching element. In particular, burning of food can be prevented. The cookware is used in particular for cooking or frying. Furthermore, when using the thermoelectric switching element, especially in a cookware, the advantageousProperties of the first layer, at least partially consisting of nickel (Ni), in particular its ferromagnetic properties, can be utilized. At the same time, the second layer can ensure that the thermoelectric switching element can also be used in applications in which nickel or nickel-containing materials are disadvantageous, for example because their use would lead to contamination of substances, such as food or drinking water. In particular, in such applications, the second layer can be in contact with the substances and preferably serve as a barrier between them and the first layer, so that contact between the substances and nickel does not occur, thus avoiding possible contamination. Various further preferred embodiments of the thermoelectric switching element and the method for producing a thermoelectric switching element are described below.wherein the various embodiments can be combined with one another and apply accordingly to embodiments of the thermoelectric switching element and to the method. Furthermore, the described preferred embodiments also apply to the already described uses of a thermoelectric switching element. According to a first embodiment of the thermoelectric switching element, a switching mechanism is provided which is designed to trigger due to the changed material properties of the ferromagnetic material of the first layer when the Curie temperature Tc of the ferromagnetic material is reached. In particular, according to this embodiment, a switching mechanism triggers due to the changed material properties of the ferromagnetic material of the first layer when the Curie temperature Tc of the ferromagnetic material is reached. The switching mechanism can, for example, be based on a magnetic circuit passing through thereversible phase transition at Tc. The switching mechanism can also be based on a material parameter of the ferromagnetic material, such as the specific resistance, which is measured, for example, by means of a sensor or measuring element provided for this purpose, changing during the reversible phase transition and this change being used as a switching signal. For this purpose, the switching mechanism can contain a resistance measuring element. Furthermore, the switching mechanism can contain a magnetic sensor that detects the reversible phase transition due to the loss of ferromagnetism of the material of the first layer. It is also possible to use the magnetism itself, which is lost or added during the phase transition due to the ferromagnetism of the ferromagnetic material, as a switching mechanism, for example to stop or (re)start inductive heating.start. According to a further embodiment of the thermoelectric switching element, a third layer is provided, at least partially consisting of a metallic material, and the third layer is connected to the first layer or the second layer, optionally via an intermediate layer, in particular by an adhesive bond with atomic diffusion. The optional intermediate layer can in particular be designed as an (electrically conductive) metallic layer. However, the third layer can also be connected directly to the first layer or the second layer, without an intermediate layer arranged therebetween. Furthermore, it is possible for the third layer to be adhesively bonded to the first layer or the second layer, for example, via an intermediate layer; in this case, the intermediate layer represents in particular an insulating intermediate layer and functions as an adhesive layer. In particular, the metallic material of the third layer differs from the materials of the first and second layers. Preferablythe metallic material of the third layer has a thermal expansion coefficient that differs from the materials of the first and second layers. According to a further embodiment of the thermoelectric switching element, the third layer has at least: a resistance region at least partially consisting of a metallic material, and two conducting regions that at least partially consist of a metallic material that differs from the metallic material of the resistance region, wherein the conducting regions are each arranged adjacent to different sides of the resistance region and are connected to the resistance region. In addition to the one resistance region and the two conducting regions, further resistance regions and / or conducting regions can be provided. The third layer can have a thickness of 10 mm or less, preferably 8 mm or less. In this way, a thermoelectricA switching element is provided which combines in one component switching mechanisms based on different thermal expansion coefficients, based on the reversible phase transition at Tc, and the function as a measuring resistor (shunt). In addition, further switching mechanisms based on (thermo-)electrical properties of the, in particular different, materials of the thermoelectric switching element can be realized by the combination of the first, second and third layers by the thermoelectric switching element, for example, based on the Seebeck effect, the induction of an electrical voltage at a temperature difference between the contact points of the layers. In particular, it can be provided for this purpose that the materials of the three layers are selected such that they have different electrical conductivities. According to a further embodiment of the thermoelectric switching element, the resistance region withThe two conductive regions are each connected by an adhesive bond with atomic diffusion. In this way, inhomogeneities at the transitions between the resistance region and the conductive regions can be reduced, so that the connection of the resistance region with the two conductive regions can provide a high-quality and high-precision nominal resistance through the thermoelectric switching element. According to a further embodiment of the switching element, the resistance region runs at the interface to one of the two conductive regions at an obtuse or acute angle α relative to a plane along at least one RO / sw 230689WO December 12, 2024 side surface of the resistance region. In this way, a reliable connection between the conductive regions, in particular those arranged next to one another and partially overlapping, and the resistance region can be achieved. In addition, further resistance regions can also be used.and conductive regions may be provided, for which the same applies with regard to the adhesive bond with atomic diffusion as well as with regard to the course of the interfaces of the resistance region relative to one or more conductive regions. An obtuse or acute angle is understood to be an angle that is not rectangular, i.e., that is greater or less than 90°. For example, an acute angle can be 89° or less and an obtuse angle 91° or more. According to a further embodiment of the thermoelectric switching element, the ferromagnetic material of the first layer consists at least partially of nickel (Ni) or a nickel alloy. In this way, the advantageous properties of the first layer, which consists at least partially of nickel (Ni), in particular its ferromagnetic properties, can be utilized, wherein at the same time the second layer or the further layer ensures that the thermoelectric switching element also inIt can be used in applications where nickel or nickel-containing materials are disadvantageous, for example, because their use would lead to contamination of substances, such as food or drinking water. In particular, in such applications, the second or further layer can be in contact with the substances and preferably serve as a barrier between them and the first layer, preventing contact between the substances and nickel and thus avoiding potential contamination. More preferably, the ferromagnetic material of the first layer consists of a nickel alloy. A bimetallic alloy with Ni is particularly preferred, but alloys with Ni and two or more other elements are also possible. Preferred alloying elements for a nickel alloy are, for example, copper (Cu), palladium (Pd), platinum (Pt), zinc (Zn), aluminum (Al), antimony (Sb), silicon (Si), molybdenum (Mo), gold.(Au), manganese (Mn), vanadium (V), chromium (Cr), titanium (Ti), and tin (Sn). It has been found that by alloying nickel with these alloying elements, the Curie temperature Tc of the alloy can be specifically adjusted to values ​​below or above the Curie temperature Tc of nickel. Furthermore, the first layer can also consist essentially entirely of nickel (Ni), so that the first layer essentially has the Curie temperature Tc of Ni, which is stated in the literature to be approximately 360 °C. In particular, an alloy of nickel (Ni) with an element selected from copper (Cu), manganese (Mn), aluminum (Al), or zinc (Zn) is preferred as the ferromagnetic material of the first layer. The alloy can be a binary alloy with Ni and one of the aforementioned elements. For example, the Curie temperature Tc of Ni can be advantageously reduced by alloying with Mn to temperatures below 300 °C, with a Mn content between 5 and 10 at.% in theAlloy, down to below 100°C, with a Mn content of between 15 and 20 at.% in the alloy. The alloy can also be a ternary or quaternary alloy or an alloy comprising more than four different elements. The alloying elements Cu, Mn, Al, and Zn already mentioned are preferred alloying elements. Furthermore, a Fe-Cr-Ni-Mn alloy can be provided as the nickel alloy for the ferromagnetic material of the first layer, so that the first layer can at least partially combine the advantageous properties of these elements, for example, the passivating properties of Cr. Further preferred, especially as a material with a Curie temperature Tc that is lower than that of pure Ni, is an Fe-Cr-Ni-Mn-Si alloy. A composition with a content of 10 wt.% Cr, 33 wt.% Ni, 53.5 wt.% Cr, 3 wt.% Mn, and 0.5 wt.% Cr is particularly advantageous for such an alloy.It was found that, in particular, the addition of 2-3 wt.% Mn to an Fe-Cr-Ni-Mn or an Fe-Cr-Ni-Mn-Si alloy is advantageous for achieving a low Curie temperature, in particular a Curie temperature of less than 100 °C, preferably less than 50 °C. RO / sw 230689WO December 12, 2024 According to a further embodiment of the thermoelectric switching element, the ferromagnetic material of the first layer has a Curie temperature Tc of less than 360 °C, preferably less than 350 °C, particularly preferably less than 330 °C. Thus, the thermoelectric switching element can be used in applications in which certain limit temperatures, in particular those below 360 °C, or 350 °C or 330 °C, should not be exceeded. For example, it is advantageous for use in handling temperature-sensitive substances such as organisms or food. Preferably, the thermoelectric switching element can have a Curie temperature Tc in the rangefrom 260 °C to 350 °C, particularly preferably in the range from 280 °C to 300 °C. These specific ranges allow for dedicated temperature limitation, for example when used to heat materials, such as food, or when used as a temperature controller. However, it is also possible for the thermocouple to have a Curie temperature Tc of 260 °C or below, preferably 200 °C or below. This is particularly advantageous when preparing temperature-sensitive foods or foods whose preparation preferably takes place at temperatures of 260 °C, preferably 200 °C, and below. Preferred alloying elements for the ferromagnetic material of the first layer, in particular for achieving a Curie temperature Tc of 260 °C or below, preferably of 200 °C or below, are, for example, copper (Cu), manganese (Mn), aluminum (Al), indium (In), strontium (Sr), nickel (Ni), antimony (Sb), calcium(Ca), silicon (Si), gallium (Ga), germanium (Ge), palladium (Pd), vanadium (V) or iron (Fe), in particular a combination of the above-mentioned elements. Alternatively, it can also be provided that the ferromagnetic material of the first layer has a Curie temperature Tc in the range of more than 360°C, preferably more than 370°C, particularly preferably more than 390°C. In this case, for example, a higher temperature at which the switching mechanism is triggered, for example a heating process is stopped, can be set. For this purpose, the ferromagnetic material can in particular comprise manganese (Mn). Preferably, the metallic material of the second and / or third layer consists essentially of a metal. In this way, a thermoelectric switching element can be achieved, the properties of which can be easily adjusted, at least on the side of the second and / or third layer. This is because a material thatConsists essentially of a metal, generally has known properties. Furthermore, the interaction of the materials of the layers can be more easily determined and controlled in this way. For example, the metallic material of the second and / or third layer can consist essentially of copper (Cu). Copper is characterized by good thermal conductivity, so that good heat distribution can be achieved, for example, in an electronic component or a cooking utensil. As a further example, it is possible for the metallic material of the second and / or third layer to consist essentially of silver (Ag). Silver is characterized by its antibacterial or antiviral effect, so that in this way a thermoelectric switching element with antibacterial or antiviral effect can be achieved. According to a further embodiment, the metallic material of the second and / or third layer consists essentially ofa metallic alloy. The use of an alloy allows for greater variability and thus the possibility of adapting the material properties of the thermoelectric switching element to a specific application. In this way, various elements with their specific advantageous properties can be incorporated into the material composite. For example, the metallic material of the second and / or third layer can consist essentially of a Cu alloy or an Ag alloy. RO / sw 230689WO December 12, 2024 Furthermore, the metallic material of the second and / or third layer is preferably selected from stainless steel. Due to its advantageous properties, such as corrosion resistance, stainless steel is used in a wide variety of areas, for example in the field of cookware. In this way, a thermoelectric switching element can be achieved in which the advantageous properties of stainless steel are incorporated into the composite.Such a flat composite part is suitable, for example, for uses in food processing, in particular food preparation, where the flat composite part comes into contact with food at least on the side of the second and / or third layer, or for applications in the sanitary sector, for example in shower heads or similar devices where water is heated or heated water is used. It can be provided that the metallic material of the second and / or third layer is not ferromagnetic, so that the use of the thermoelectric switching element, for example as an electromagnetic component, is not influenced by the magnetic properties of the material of the first layer. According to a first embodiment of the method, the second layer is provided by: one layer at least partially consisting of a metallic material (resistance material) and two layersat least partially consisting of a further metallic material (conducting material) are provided and arranged next to one another, wherein the layer at least partially consisting of the resistance material is arranged between the two layers at least partially consisting of the conducting material in such a way that the layer at least partially consisting of the resistance material at least partially overlaps the layers at least partially consisting of the conducting material, and the layers are connected to one another by creating an adhesive bond with atomic diffusion between the layer at least partially consisting of the resistance material and the two layers at least partially consisting of the conducting material. RO / sw 230689WO December 12, 2024 A composite produced by the described method, in which adjacent layers are arranged partially overlapping next to one another and connected to one another by an adhesive bond with atomic diffusionare connected, is particularly referred to as a side-to-side (2S2) composite. In particular, such a composite has inclined interfaces between the resistance material and the conductivity material. An inclined interface is understood to be an interface that runs at an acute or obtuse angle relative to at least one side surface of the layer made of the resistance material. In particular, a high-resistance resistance alloy can be used as the resistance material, for example a nickel-chromium-based alloy, a copper-nickel-based alloy, or an iron-nickel-based alloy. In particular, a material consisting at least partially of copper can be provided as the conductivity material. In this way, a shunt can be realized through the second layer, which, due to the adhesive bond with atomic diffusion, has only a small transition zone, for example in comparison to conventionally manufactured, in particular welded, nominal resistors.Inhomogeneities at the transition between resistance material and conducting material can be minimized and thus a precise measuring resistance, in particular in conjunction with further switching mechanisms, can be provided by the thermoelectric switching element. According to a further embodiment of the method, a third layer is provided, at least partially consisting of a metallic material, the third layer is arranged adjacent to the first layer or to the second layer, optionally by means of an intermediate layer arranged between the third layer and the first layer or between the third layer and the second layer, and is arranged between the third layer and the first layer or between the third layer and the second layer, optionally in each case by means of the generation of an adhesive bond with atomic diffusion between the third layer and the intermediate layer and between the first RO / sw 230689WO December 12, 2024 layer and the intermediate layer or between thesecond layer and the intermediate layer, an adhesive bond with atomic diffusion is created. According to a further embodiment of the method, the adhesive bond with atomic diffusion is created by applying pressure. By applying pressure, the surfaces of the layers to be joined can be brought into intimate contact with each other over a large area, whereby the pressure can also be applied in conjunction with other processes, for example, a forming process. The bond formed by the adhesive bond between the bonding partners is formed by mixing by atomic diffusion, forming a transition layer over which a continuous adaptation of the material properties takes place. In addition, it is possible to introduce further energy in the form of heat, which can enhance the atomic diffusion. However, an adhesive bond with atomic diffusion can also be created without additional heat input.The application of pressure, for example by pressing the bonding partners together, and the application of additional energy, for example in the form of heat, can occur simultaneously or at different times. The application of additional energy can also influence the expansion of the transition layer, although this generally depends on the respective materials of the bonding partners. Enlarging the expansion zone and increasing atomic diffusion can be used specifically to influence the material properties of the thermoelectric switching element. For example, enlarging the expansion zone and increasing atomic diffusion leads to greater mixing of the composite material, which can promote increased electrical conductivity and / or increased thermal conductivity between the layers. In addition, the application of energy and heat can specifically influence the microstructure of the composite material.be influenced. For example, a recrystallization of the materials of the layers can occur. The degree of hardening of the materials of the layers can also be influenced. The process described above can, for example, be understood as cladding, whereby in English usage the term "cladding" can predominantly be used to describe such a process. The process described above primarily creates a metallic bond between two bonding partners. An adhesive bond with atomic diffusion of metallic materials with non-metallic materials, for example carbon-containing materials, or between non-metallic materials can also be created. If no additional heat is introduced, the process can be referred to in particular as cold roll cladding; if additional energy in the form of heat is introduced, it can be referred to as hot roll cladding. According to a furtherIn some embodiments of the process, the adhesive bond is created by atomic diffusion by applying heat. It is thus also possible to create the adhesive bond by atomic diffusion without applying pressure, but rather by applying heat. Such a process can be referred to as joining by heat application. One example of such an embodiment of the process is the production of a composite of two or more metallic layers using 3D printing. Within the scope of this additive manufacturing process, heat is introduced into a metallic powder, particularly by means of lasers or electron beam devices, which can then be melted in a targeted manner at the points where heat is applied. In this way, metallic materials can be joined together at the points where heat is applied. Such a process can also be referred to as powder bed-based laser melting (laser metal fusion).Further features and advantages of the invention will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings. RO / sw 230689WO December 12, 2024 In the drawings, Fig. 1a-b shows a first exemplary embodiment of a thermoelectric switching element according to the invention, Fig. 2 shows a second exemplary embodiment of a thermoelectric switching element according to the invention, Fig. 3 shows a third exemplary embodiment of a thermoelectric switching element according to the invention, and Fig. 4 shows a fourth exemplary embodiment of a thermoelectric switching element according to the invention. In the following description of the various exemplary embodiments of the invention, components and elements with the same function and the same mode of operation are provided with the same reference numerals, even if the components and elements in the various exemplary embodiments may differ in their dimensions, shape, or nature.Fig. 1a-b schematically show a sectional view of a first embodiment of a thermoelectric switching element 2 according to the invention. Fig. 1a shows the embodiment at room temperature, and Fig. 1b shows the embodiment at a predetermined temperature T1, which is above room temperature. The thermoelectric switching element 2 has a first layer 4, which consists of a ferromagnetic material, here essentially a nickel (Ni) alloy, and a second layer 6, which consists essentially of a metallic material, here essentially copper (Cu). The materials of the first layer 4 and the second layer 6 have different thermal expansion coefficients, wherein the thermal expansion coefficients of the ferromagnetic material of the first layer 4 and the metallic material of the second layer 6 are selected in such a way, and the first layer 4 and the second layer 6 are arranged relative to one another in such a way andare connected to one another such that, upon reaching a predetermined temperature T1, a predetermined deformation of the first layer 4 and the second layer 6 is achieved. The first layer 4 and the second layer 6 are arranged flat one above the other, connected to one another by adhesive bonding with atomic diffusion, and in this example, are designed as continuous layers. The layers 4, 6 here each have constant thicknesses across the width of the illustration. However, it is also possible for the layers 4, 6 of the thermoelectric switching element 2 to vary across its width and / or length. In particular, due to the different thermal expansion coefficients of the materials of the first layer 4 and the second layer 6, upon reaching a predetermined temperature T1, a predetermined deformation of the composite is achieved such that the metal strip formed by the composite bends in one direction, in particular in the direction of the layer of the material with the lowerThis is shown in Fig. 1b. The ferromagnetic material of the first layer 4 has a lower coefficient of thermal expansion than the metallic material of the second layer 6, so that the thermoelectric switching element 2 is deformed in the direction of the first layer 4 (see arrow). Fig. 1a additionally shows a twice enlarged section 14 of the thermoelectric switching element 2, whereby the adhesive bond 10 with atomic diffusion 12 of the first layer 4 and the second layer 6 can be seen. In a first enlargement 16 of the section 14, it can be seen that the interface of the layers 4, 6 is not flat, as shown ideally in the schematic, non-enlarged view of Fig. 1a, but has an irregular profile. The adjacent layers 4, 6 therefore have a certain roughness at the atomic level at the interface, which already causes the layers 4, 6 to adhere. In aMagnification 16 In the further enlarged view of the second magnification 18, further details of the interface can be seen at the atomic level. The atoms of the materials of the layers 4, 6 are not only located on one side of the interface, but extend across the interface into the other layer 4, 6 due to diffusion. This adhesive bond 10 of the materials of the respective layers 4, 6 to be joined is initiated in particular by joint cold rolling of the layers 4, 6. During cold rolling, rollers, for example two rollers, which are arranged above and below the layers 4, 6 lying flat on top of one another, exert pressure on the layers 4, 6 to be joined, which brings the layers 4, 6 into intimate contact with one another at the atomic level. At the atomic level, as shown in the enlargement 18 of the section 14, at the interface of the layers 4, 6, aMixing of the respective materials of the layers 4, 6 takes place. After plating, the composite can optionally be heated to enable, among other things, further material migration. Fig. 2 shows a schematic sectional view of a second embodiment of a switching element 2 according to the invention, which has a first layer 4, wherein the first layer 4 consists of a ferromagnetic material, here essentially of a nickel (Ni) alloy, and which has a further layer 20. The further layer 20 has a resistance region 24, which consists essentially of a high-ohmic resistance alloy, and two conducting regions 26a, 26b, which are each arranged adjacent to different sides of the resistance region 24 and are connected to the resistance region 24 and consist of copper (Cu). The resistance region 24 runs at the interface 32a, 32b to one of the two conducting regions 26a, 26b at an acute angle α relative to a planealong at least one side surface 28 of the resistance region 24. Furthermore, an electrically conductive intermediate layer 22 is provided, which here consists of copper (Cu). The layers 4, 20, 22 are each connected to one another by an adhesive bond 10 with atomic diffusion 12. RO / sw 230689WO December 12, 2024 Due to its structure comprising a resistance region 24 and two conducting regions 26a, 26b, the further layer 20 represents a shunt resistor, wherein the two conducting regions 26a, 26b serve to contact the shunt resistor. A temperature-dependent resistance is achieved through the bond with the first layer 4 made of a ferromagnetic material having a Curie temperature Tc. The intermediate layer 22 can also be designed as an insulating intermediate layer. In this case, the resistance of the nominal resistor is not influenced by the properties of the ferromagnetic material of the first layer 4, especially temperature-dependent. At the same time,However, the switching mechanism based on the reversible phase transition upon reaching the Curie temperature Tc can be used, for example, as overheating protection when the temperatures in the vicinity of the nominal resistance (of the further layer 20) and thus the temperature of the first layer 4 reaches the temperature Tc. For example, for this purpose, current could flow through the first layer 4 and the further layer 20 in the form of a parallel circuit, whereby the current through the first layer 4, which changes due to the change in the resistivity of the ferromagnetic material upon reaching the Curie temperature Tc, can serve as a switching signal for the overheating protection. Fig. 3 shows a schematic sectional view of a third embodiment of a switching element 2 according to the invention, which has a first layer 4 made of a ferromagnetic material and a second layer 6 made of a metallic material. The composite of the first layer 4 and the second layer 6 correspondsessentially the composite of Fig. 1a. In addition, in the embodiment in Fig. 3, a third layer 8 is provided, which, corresponding to the structure of the further layer 20 of Fig. 2, has a resistance region 24 and two conducting regions 26a, 26b. In this way, a composite of two materials with different materials with a nominal resistance (shunt) corresponding to the further layer 20 is achieved, so that the various switching mechanisms RO / sw 230689WO December 12, 2024 can be used synergistically. The first layer 4 made of a ferromagnetic material can, for example, provide protection against overheating of the nominal resistance represented by the third layer 8. If, for example, the thermoelectric switching element, which comprises the layers 4, 6, 8, which are connected to one another by adhesive bonding with atomic diffusion, heats up, a switching mechanism can be activated by reaching the Curie temperature Tc of the ferromagnetic material.which warns of overheating or reduces or terminates a current flow or a heating process. At the same time, a temperature-dependent resistance is achieved through the bond with the first layer 4, because when the Curie temperature Tc is reached, the specific resistance of the ferromagnetic material changes. In addition, a switching mechanism based on the (thermo-)bimetal effect can be realized due to the different thermal expansion coefficients of at least the first layer 4 and the second layer 6. Finally, Fig. 4 shows a schematic sectional view of a fourth embodiment of a switching element 2 according to the invention, which has a first layer 4 made of a ferromagnetic material and a second layer 6 made of a metallic material. The bond between the first layer 4 and the second layer 6 essentially corresponds to the bond in Fig. 1a. In addition, in the embodiment in Fig. 4, a third layer 8 is provided, which has ahas a thermal expansion coefficient that differs from the materials of the first layer 4 and the second layer 6. In this way, a composite of materials with at least three different thermal expansion coefficients is achieved. For example, the thermal expansion coefficient of the second layer 6 can be greater than the thermal expansion coefficient of the first layer 4, and the thermal expansion coefficient of the third layer 8 can be greater than the thermal expansion coefficient of the second layer 6, so that a gradual gradation of the thermal expansion coefficients is achieved. In this way, deformation of the composite can be achieved with temperature changes, during which the tensile stresses between the individual layers can be reduced, so that a more stable thermoelectric switching element 2 can be achieved. RO / sw 230689WO December 12, 2024

Claims

December 12, 2024 P a t e n t a n s p r ü c h e1. A thermoelectric switching element (2), - with a first layer (4) at least partially consisting of a ferromagnetic material, and - with a second layer (6) at least partially consisting of a metallic material, - wherein the ferromagnetic material of the first layer (4) and the metallic material of the second layer (6) have different thermal expansion coefficients, and - wherein the thermal expansion coefficient of the ferromagnetic material of the first layer (4) and the thermal expansion coefficient of the metallic material of the second layer (6) are selected and the first layer (4) and the second layer (6) are connected to one another and arranged relative to one another in such a way that, upon reaching a predetermined temperature, a predetermined deformation of the composite of the first layer (4) and the second layer (6) is achieved, characterized in that - the first layer (4) and the second layer (6) are connected by an adhesive bond (10) with atomic diffusion (12),optionally via an intermediate layer (22).

2. Thermoelectric switching element (2), - with a first layer (4) at least partially consisting of a ferromagnetic material, and - with a further layer (20) which has at least: - a resistance region (24) at least partially consisting of a metallic material, and, - 2 - - two conductive regions (26a, 26b), which consist at least partially of a metallic material different from the metallic material of the resistance region (24), - wherein the conductive regions (26a, 26b) are each arranged adjacent to different sides of the resistance region (24) and are connected to the resistance region (24), characterized in that - the first layer (4) and the further layer (20) are connected to one another by an adhesive bond (10) with atomic diffusion (12), optionally via an intermediate layer (22).

3. Thermoelectric switching element (2) according to claim 1 or 2, characterized in that - a switching mechanism is provided which is configured to trigger due to the changed material properties of the ferromagnetic material of the first layer (4) when the Curie temperature Tc of the ferromagnetic material is reached. 4.Thermoelectric switching element (2) according to one of claims 1 to 3, characterized in that - a third layer (8) is provided, consisting at least partially of a metallic material, and - the third layer (8) is connected to the first layer (4) or the second layer (6), optionally via an intermediate layer (22), in particular by an adhesive bond (10) with atomic diffusion (12).

5. Thermoelectric switching element (2) according to claim 4, characterized in that - the third layer (8) has at least: - a resistance region (24) consisting at least partially of a metallic material, and RO / sw 230689WO December 12, 2024. - 3 - - two conductive regions (26a, 26b), which consist at least partially of a metallic material different from the metallic material of the resistance region, - wherein the conductive regions (26a, 26b) are each arranged adjacent to different sides of the resistance region (24) and are connected to the resistance region (26a, 26b).

6. Thermoelectric switching element (2) according to one of claims 2 to 5, characterized in that - the resistance region (24) is connected to the two conductive regions (26a, 26b) by an adhesive bond (10) with atomic diffusion (12).

7. Thermoelectric switching element (2) according to claim 6, characterized in that the resistance region (24) extends at the interface (32a, 32b) to one of the two conducting regions (26a, 26b) at an obtuse or acute angle α relative to a plane along at least one side surface (28) of the resistance region (24).Thermoelectric switching element (2) according to one of claims 1 to 7, characterized in that - the ferromagnetic material of the first layer (4) consists at least partially of nickel (Ni) or a nickel alloy.

9. Thermoelectric switching element (2) according to one of claims 1 to 8, characterized in that - the ferromagnetic material of the first layer (4) has a Curie temperature Tc of less than 360°C, preferably less than 350°C, particularly preferably less than 330°C. RO / sw 230689WO December 12, 2024. - 4 - 10. Use of a thermoelectric switching element (2) according to one of claims 1 to 9 as overheating protection.

11. A method for producing a thermoelectric switching element (2), in particular a thermoelectric switching element (2) according to one of claims 1 to 9, - in which a first layer (4) is provided, at least partially consisting of a ferromagnetic material, - in which a second layer (6, 20) is provided, at least partially consisting of a metallic material, - in which an intermediate layer (22) is optionally provided, - in which the first layer (4) and the second layer (6, 20) are arranged adjacent to one another, optionally by means of the intermediate layer (22) arranged between the first layer (4) and the second layer (6, 20), and - in which between the first layer (4) and the second layer (6, 22),optionally, an adhesive bond (10) with atomic diffusion (12) is created between the first layer (4) and the intermediate layer (6) and between the second layer (6, 22) and the intermediate layer (6).

12. The method according to claim 11, - in which the second layer (20) is provided by: - ​​providing a layer (24) at least partially consisting of a metallic material (resistance material) and two layers (26a, 26b) at least partially consisting of a further metallic material (conducting material) and arranging them next to one another, wherein the layer (24) at least partially consisting of the resistance material is arranged between the two layers (26a, 26b) at least partially consisting of the conducting material in such a way that the layer (24) at least partially consisting of the resistance material is in contact with the layers (26a, 26b) at least RO / sw 230689WO December 12, 2024, - 5 - partially consisting of the conductive material at least partially overlaps, and - the layers (24, 26a, 26b) are connected to one another by creating an adhesive bond (10) with atomic diffusion (12) between the layer (24) at least partially consisting of the resistance material and the two layers (26a, 26b) at least partially consisting of the conductive material. 13.Method according to claim 11 or 12, - in which a third layer (8) is provided which consists at least partially of a metallic material, - in which the third layer (8) is arranged adjacent to the first layer (4) or to the second layer (6), optionally by means of an intermediate layer (22) arranged between the third layer (8) and the first layer (4) or between the third layer (8) and the second layer (6), and - in which an adhesive bond (10) with atomic diffusion (12) is created between the third layer (8) and the first layer (4) or between the third layer (8) and the second layer (6), optionally in each case by means of the creation of an adhesive bond (10) with atomic diffusion (12) between the third layer (8) and the intermediate layer (22) and between the first layer (4) and the intermediate layer (22) or between the second layer (6) and the intermediate layer (22).Method according to one of claims 11 to 13, - in which the adhesive bond (10) with atomic diffusion (12) is created by applying pressure.

15. Method according to one of claims 11 to 13, - in which the adhesive bond (10) with atomic diffusion (12) is created by applying heat. RO / sw 230689WO December 12, 2024.

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