Piezoelectric Components

Abstract

The invention relates to a piezoelectric component (1) comprising a piezoelectric layer (4) having a polycrystalline piezoelectric ceramic material with a coercive force of at least 1.8 kV / mm and a carrier element (2) on which the piezoelectric layer (4) is arranged and to which the piezoelectric layer (4) is mechanically coupled.

Description

[Technical field]

[0001] The present invention relates to piezoelectric components, applications of lead-free ceramics in piezoelectric components, and manufacturing methods. [Background technology]

[0002] The piezoelectric effect is used in a variety of applications, such as tactile sensors and actuators, acoustic sensors and actuators, ultrasonic transducers, or "energy harvesting". The piezoelectric elements required for this are usually made of the ceramic material lead zirconate titanate (Pb u Zr v Ti w O x ) as described, for example, in DE 10 2009 030 710 A1.

[0003] However, due to the material properties of piezoelectric elements, they must physically have a certain minimum thickness, which requires complex processing (high sintering temperatures, high material usage).

[0004] Additionally, these devices contain high concentrations of lead, a heavy metal that is harmful to the environment.

[0005] These adverse properties can be compensated for by using alternative materials such as piezo-active plastics and lead-free piezoelectric ceramics. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent Application Publication No. 102009030710 Summary of the Invention [Problem to be solved by the invention]

[0007] It is therefore an object of the present invention to provide an alternative piezoelectric component with an improved piezoelectric layer. [Means for solving the problem]

[0008] According to the invention there is provided a piezoelectric component comprising a piezoelectric layer, said piezoelectric layer preferably having a polycrystalline ceramic material with a coercive force of at least 1.8 kV / mm, preferably in the range of 2 kV / mm to 10 kV / mm, more preferably in the range of 2 kV / mm to 5 kV / mm. The component further comprises a carrier element on which the piezoelectric layer is arranged and mechanically coupled to the piezoelectric layer. The component is therefore preferably designed such that both the carrier element and the piezoelectric layer deform when excited.

[0009] The coercivity of the piezoelectric layer may correspond to the coercivity of a polycrystalline ceramic material.

[0010] The piezoelectric layer preferably has a layer thickness of at least 40 μm or at least 50 μm.The piezoelectric layer is preferably manufactured by a film process which involves stretching a film followed by poling in an electric field.

[0011] In addition to piezoelectric layers containing ceramics with a polycrystalline structure, embodiments using plastic-based piezoelectric layers or layers combining ceramics and plastics are also possible. By selectively adding piezoelectric plastics, the coercivity of the piezoelectric layer can be selectively increased up to 125 kV / mm.

[0012] Ceramic thin films, especially those with a structure similar to that of a single crystal, produced for example by sol-gel or chemical vapor deposition (e.g. CVD or ADL), are not suitable for the piezoelectric layer of the present invention, since the mechanical stability of the bond with the carrier element is insufficient for the applications described below. The properties of such ceramic thin films, especially when they have a structure similar to that of a single crystal, are governed by the intracrystalline interactions occurring in the ceramic material, such as covalent or ionic bonds. They are usually characterized by a high coercive force of more than 10 kV / mm, but may also have mechanical stresses in the ceramic thin film due to non-epitaxial growth.

[0013] Especially in actuator and sensor applications, the piezoelectric layer is subjected to large tensile and compressive forces that exceed the material properties of ceramic thin films, especially those with a single crystal structure, which can crack due to mechanical stress, resulting in the component becoming electrically and / or mechanically unusable.

[0014] The invention therefore relates more particularly to an improvement of a piezoelectric layer of ceramics with a polycrystalline structure. The coercivity of a piezoelectric layer with a polycrystalline structure depends mainly on the intercrystalline interactions in the crystal lattice. Previously known piezoelectric layers made of ceramics with a polycrystalline structure usually have a coercivity of up to 3 kV / mm. By combining suitable materials with suitable thin films, the coercivity of the piezoelectric layer according to the invention can be maximized. At the same time, it is also possible to obtain a resistance to mechanical stress of the polycrystalline ceramic layer compared to ceramic thin films.

[0015] In other words, the material properties of piezoelectric ceramics that have a single crystal structure or a structure similar to a single crystal (the material properties are the same as those of a crystal, and intra-crystal interactions are dominant) are significantly different from those of piezoelectric ceramics that have a polycrystalline structure (where inter-crystal interactions are dominant), and they cannot be interchanged.

[0016] Alternative components relating to piezoelectric ceramics having a single crystal structure are known, for example from WO 2021 / 249844 or US 2015 / 0054870 or US 2006 / 0119229.

[0017] In the film process for producing piezoelectric layers, the raw material is provided as a powder in the first step. A green film is produced from the powder by delivering adhesive and solvent, followed by mixing, stretching the film and drying. Individual green parts can then be punched out of the film. Alternatively, the entire film can be further processed as a green part. The green part is then converted into a ceramic part by heat treatment. During the heat treatment, the green part is decarburized and sintered, after which it is cooled.

[0018] A subsequent external activation process involves placing electrodes on the ceramic parts to polarize them, producing a piezoelectric layer with application-relevant piezoelectric functionality.

[0019] For example, the poling is performed in air or in a liquid / gas insulating medium, preferably at a temperature between room temperature and 120° C., with a poling field strength of, for example, 3.5 kV / mm to 5 kV / mm. For example, the poling is performed in air at 90° C., with 3.5 kV / mm. The poling temperature is therefore much lower than the Curie temperature of the piezoelectric layer.

[0020] The piezoelectric layer may then be deposited on a carrier element. The actuator / sensor or transducer thus fabricated may, for example, operate at temperatures between room temperature and 270° C. at electric fields up to 3 kV / mm.

[0021] Exciting the piezoelectric layer may specifically include applying an electric field to the piezoelectric layer.

[0022] In this case, when the piezoelectric layer deforms, the carrier element mechanically coupled to it also deforms, so that the carrier element functions as a mechanical actuator.

[0023] When the carrier element is mechanically deformed, for example by mechanical pressure or acoustic waves, the piezoelectric layer mechanically coupled thereto is also deformed, thereby generating an electrical signal, in which case the component functions as a sensor.

[0024] In either case, the components act as transducers of mechanical and electrical energy.

[0025] In one embodiment, two different electrodes may be disposed on the surface of the piezoelectric layer, and in operation, when a voltage is applied, the two electrodes will have different polarities.

[0026] An electric field may be applied to the piezoelectric layer by means of electrodes and an electrical signal, in particular a voltage, may be picked up from the piezoelectric layer.

[0027] Application of an electric field to the piezoelectric layer can, among other things, cause a mechanical deformation of the layer, whereas application of a mechanical force to the piezoelectric layer can generate an electrical signal that can be picked up.

[0028] The two electrodes are advantageously disk-shaped and are arranged on opposite surfaces of the piezoelectric layer. They are in particular arranged over the entire surface, so that an electric field can be applied or picked up that extends over the entire thickness of the piezoelectric layer. In one embodiment, the electrodes do not completely cover the opposite surfaces, but the surfaces have free edges, i.e. parts without electrodes, so that the electrodes protrude.

[0029] At least one of the piezoelectric layer and the electrode is preferably disk-shaped. Here, the diameter of the disk-shaped piezoelectric layer and the diameter of the disk-shaped electrode may be the same or different. The radius of the disk-shaped electrode is preferably 500 μm or less smaller than the radius of the disk-shaped piezoelectric element.

[0030] In one embodiment, at least one of the electrodes extends to a side of the piezoelectric layer and, optionally, to the opposite surface, thereby providing electrodes on both of the opposite surfaces. In this way, the electrodes can be electrically connected from both sides. In one embodiment, the two electrodes may be correspondingly positioned, but the electrodes must not be in direct contact with each other.

[0031] The carrier element, which may be realized as a membrane, is preferably electrically conductive and comprises a conductive material, for example a metal, such as brass, aluminum, titanium, copper or steel, a carbon fibre material, etc. Alternatively, the carrier element may comprise, for example, a plastic material or glass fibre reinforced plastic (GRP), for example with a metallised surface or containing conductive particles.

[0032] Preferably, the piezoelectric layer or one of the electrodes on the surface of the piezoelectric layer is arranged in a force-fit manner on the carrier element.

[0033] In one embodiment, the piezoelectric layer or one of the electrodes on the surface of the piezoelectric layer is arranged on the carrier element in the manner of material bonding. For this purpose, for example, a connection layer of adhesive material is provided between the piezoelectric layer and the carrier element. The adhesive material may be non-conductive, anisotropically conductive (i.e. preferably conductive in the direction between the carrier element and the electrode and non-conductive in the direction perpendicular thereto), or conductive.

[0034] In one embodiment, the piezoelectric layer and the electrodes disposed thereon are formed as a circular or elliptical plate, or the piezoelectric layer and the electrodes disposed thereon are formed as a triangle, a square, a pentagon, a hexagon, or an n-gon (where n is a natural number greater than 6).

[0035] Preferably, the piezoelectric component further comprises a carrier element, e.g. a membrane, on which the piezoelectric layer may be arranged. The membrane may be circular like the piezoelectric layer or may have a different geometric shape than the piezoelectric layer.

[0036] The carrier element or membrane is preferably one of the electrodes arranged on the surface of the piezoelectric layer. For this purpose, the carrier element is electrically conductive. The carrier element and the piezoelectric layer are connected in the manner of a material bond, for example by soldering, fusion welding, gluing (preferably with a conductive adhesive) or simultaneous sintering.

[0037] External electrical excitation, in particular the application of an electric field, for example by electrodes arranged on the surface of the piezoelectric layer, will result in the layer contracting or expanding due to the piezoelectric effect. In most applications, the contraction or expansion is preferably directional, either along the layer thickness direction or perpendicularly along the layer plane direction, although the solutions presented here allow in principle contraction or expansion in any other direction, which is mainly determined by the geometry of the layer.

[0038] For this purpose, the piezoelectric layer undergoes a change in expansion when an electric field is applied to it, for example by applying a voltage to electrodes arranged on the two surfaces of the layer.

[0039] Forces acting on a carrier element, such as a membrane, as a result of changes in the expansion of the piezoelectric layer create bending moments, causing movement perpendicular to the base plane of the component, which movement is used in the desired application.

[0040] When an electric field is applied to the piezoelectric layer, in particular the expansion of the piezoelectric layer changes, preferably in the layer plane of the piezoelectric layer.

[0041] For example, if a circular piezoelectric layer plane is employed, the diameter of the piezoelectric layer may vary. In particular, if the circular piezoelectric layer operates as a radial transducer, the diameter of the piezoelectric layer varies. The coupling between the piezoelectric layer and the carrier element causes a displacement of the composite of the piezoelectric layer and the carrier element in a direction perpendicular to the layer plane of the piezoelectric layer. That is, the expansion of the piezoelectric layer arranged on the carrier element causes a bending moment, which causes a displacement of the carrier element in a direction perpendicular to the layer plane of the piezoelectric layer.

[0042] Therefore, the maximum displacement of a carrier element with diameter D in the direction z perpendicular to the layer plane depends on the properties of the piezoelectric layer, in particular the thickness t p , the piezoelectric constant d31, the Poisson's ratio ν as the exponent of the lateral contraction coefficient, and the elastic modulus (E-modulus) E of the piezoelectric layer. p , as well as the characteristics of the carrier element, in particular the thickness t c and the E-modulus E of the carrier element c Depends on.

[0043] Maximum displacement A in direction z displacement is determined approximately by the following formula:

number

[0044] In particular, due to the form-fit and material bond connection of the piezoelectric layer and the carrier material, for example by adhesive, the sensor / actuator / transducer etc. may be considered as a composite material.

[0045] Based on the analytical relationships mentioned above and the resulting interactions between each of the components, the desired electromechanical properties have to be adjusted, for example by changing the geometry or the carrier material. That is, not only the ceramic properties but also the interactions mentioned above, for example, affect the operational performance of the actuator / sensor / transducer etc.

[0046] In sensor applications, the opposite of the actuator applications described above is true: a force in the longitudinal direction acting on the piezoelectric layer creates a bending moment that generates a measurable voltage that can be read or picked up.

[0047] To realize a displacement of a component consisting of a piezoelectric layer and a carrier element from its rest position, a neutral phase of the composite component must be located within the piezoelectric layer, where the neutral phase refers to an imaginary line where there is no deformation.

[0048] In particular, it is affected by dimensions and ratios such as the thickness and diameter of the layer, the thickness and diameter of the carrier element, the ratio of the thickness of the layer to the carrier element, the ratio of the diameter of the layer to the carrier element, the center-to-center distance between the layer and the carrier element, the E-modulus of the layer and the carrier element, the Poisson's ratio of the layer and the carrier element, the 3D geometric dimensions of the layer and the carrier element, the acoustic impedance of the layer and the carrier element, the spring constant of the layer and the carrier element, and the thickness and elastic mechanical properties of the connecting layer between the carrier element and the piezoelectric layer, and therefore need to be selected appropriately.

[0049] The component according to the invention is preferably a radial oscillator.

[0050] The difference between radial and thickness transducers essentially lies in the different dimensional ratios of diameter to thickness.

[0051] The diameter / thickness ratio of the piezoelectric layer of the radial transducer is equal to or greater than 10. The diameter / thickness ratio of the piezoelectric layer of the thickness transducer is equal to or smaller than 10.

[0052] In a radial transducer, when a voltage is applied, the diameter of the piezoelectric layer changes relative to its original diameter, which is given by the piezoelectric constant d31.

[0053] To generate a movement in the thickness direction of the piezoelectric layer, a carrier element as described above is required. The carrier material and the component consisting of the piezoelectric layer and the carrier material are optimized for the respective application, for example in terms of charge generation, impedance and / or displacement.

[0054] On the other hand, the characteristics of a thickness vibrator are expressed by the piezoelectric constant d33 and the applied voltage. Here, the ceramic is directly compressed or stretched in the thickness direction. Therefore, the thickness vibrator does not require a carrier material and can be used independently. For example, European Patent No. 3372571 describes an example of a thickness vibrator.

[0055] The radial transducer can be used in a wider range of applications due to its composite properties. As mentioned above, the radial transducer can be used as an actuator, a sensor, or a transducer.

[0056] In addition to the location of the neutral phase, the above dimensions also affect properties of the piezoelectric component such as the allowable control voltage, resonant frequency, allowable ceramic compressive and tensile stresses, blocking force, quality, impedance, capacitance and charge generation, acoustic impedance, spring characteristics, mechanical damping, efficiency of "electrical-mechanical" conversion, efficiency of "mechanical-electrical" conversion, and displacement and acceleration.

[0057] The piezoelectric layer is particularly characterized by the above-mentioned high coercive force, which allows the thickness of the piezoelectric layer in the piezoelectric component to be reduced without changing other requirements. For example, the material usage in the manufacturing process can be reduced by about 30 percent while maintaining the functionality of the component. This reduces manufacturing costs and raw material consumption.

[0058] Therefore, the piezoelectric layer is preferably suitable for manufacturing thin piezoelectric components. Therefore, a polycrystalline piezoelectric ceramic material having a high coercive force is preferably used to form the piezoelectric layer. The coercive force of the piezoelectric layer can be equivalent to that of the polycrystalline piezoelectric ceramic material. The coercive force of the piezoelectric layer can be increased up to 125 kV / mm by adding a piezoelectric plastic.

[0059] Furthermore, due to the low sintering temperature for producing the above polycrystalline piezoelectric ceramic material from green layers, the production can be carried out with low energy consumption and therefore at low cost.

[0060] The sintering temperature is, for example, lower than 1050° C., preferably lower than 1030° C. The sintering temperature is preferably higher than 900° C., particularly within the range of 900° C. to 1030° C.

[0061] The sintering temperature of the piezoelectric layer may correspond to the sintering temperature of a polycrystalline piezoelectric ceramic material.

[0062] The green layer is therefore particularly suitable for being placed and subsequently co-sintered with a carrier element or membrane that is sensitive to high temperatures.

[0063] The green layers described above are furthermore suitable for forming ceramic films, so that piezoelectric layers with the desired small layer thickness can be realized simply by film technology, i.e. by laminating and pressing preformed films. The piezoelectric layer may also only comprise a film of the corresponding thickness. By using a single thick film, lamination and pressing can be omitted, simplifying the manufacturing process. In this case, cutting processes such as grinding or lapping for achieving the desired thickness can be omitted. This allows further material and resource savings in the manufacturing process and reduces the number of operating steps required for this.

[0064] In a preferred embodiment, the electromechanical coupling coefficient k31 of the polycrystalline piezoelectric ceramic material is in the range of 0.2 to 0.3, preferably in the range of 0.25 to 0.3, and particularly preferably 0.27. The electromechanical coupling coefficient k31 of the piezoelectric layer may correspond to the electromechanical coupling coefficient k31 of the polycrystalline piezoelectric ceramic material.

[0065] In another preferred embodiment, the density of the polycrystalline piezoelectric ceramic material is 7000 kg / m 3 ~7500kg / m 3 The density of the piezoelectric layer may correspond to the density of a polycrystalline piezoelectric ceramic material.

[0066] In another preferred embodiment, the dielectric constant or permittivity coefficient ε of the polycrystalline piezoelectric ceramic material in the polarization direction is r =ε33 / ε0 is smaller than 1100, preferably smaller than 1000, particularly preferably in the range of 800 to 1100, more preferably in the range of 900 to 1000, and further preferably in the range of 910 to 950. The dielectric constant coefficient ε of the piezoelectric layer r is the dielectric constant ε of the polycrystalline piezoelectric ceramic material rBy adding piezoelectric plastic, the dielectric constant coefficient ε of the piezoelectric layer can be increased. r can be reduced to a maximum of 8.

[0067] In another preferred embodiment, the piezoelectric constant d31 of the polycrystalline piezoelectric ceramic material is less than 100 pm / V, preferably in the range of 50 pm / V to 100 pm / V, preferably in the range of 70 pm / V to 90 pm / V. The piezoelectric constant d31 of the piezoelectric layer may correspond to the piezoelectric constant d31 of the polycrystalline piezoelectric ceramic material. The piezoelectric constant of a piezoelectric layer made of a piezoelectric plastic such as PVDF (polyvinylidene fluoride) is in the range of about 10 pm / V to 12 pm / V. Therefore, the piezoelectric constant d31 of the piezoelectric layer can be further reduced by adding a piezoelectric plastic.

[0068] In another preferred embodiment, the Curie temperature of the polycrystalline piezoelectric ceramic material is in the range of 400 to 500° C. Here, the Curie temperature of the piezoelectric layer may correspond to the Curie temperature of the polycrystalline piezoelectric ceramic material.

[0069] In another preferred embodiment, the mechanical quality Qm of the polycrystalline piezoelectric ceramic material is in the range of 50 to 100, preferably in the range of 50 to 70, preferably 60. The mechanical quality Qm of the piezoelectric layer may correspond to the mechanical quality Qm of the polycrystalline piezoelectric ceramic material.

[0070] In another preferred embodiment, the elastic modulus E of the carrier element is in the range of 0.1 GPa to 1000 GPa, preferably in the range of 60 GPa to 215 GPa, preferably in the range of 100 GPa to 180 GPa.

[0071] The ratio of the elastic modulus of the carrier element to the elastic modulus of the piezoelectric layer is preferably in the range of 0.0004 to 3000. This allows a desired mechanical interaction to be achieved between the carrier element and the piezoelectric layer. When the carrier element deforms, the piezoelectric layer deforms accordingly and vice versa.

[0072] The piezoelectric layer preferably does not include internal structural elements such as internal electrodes or metallization layers.

[0073] In a preferred embodiment, the piezoelectric layer is made of (Bi x FeO 3 ) 1-a (Ba y TiO 3 ) a where 0.20≦a≦0.50, 0.90≦x≦1.10 and 0.90≦y≦1.01. In this case, the piezoelectric layer may be substantially formed from or may consist of such a ceramic material. Here, the ceramic material is preferably formed as a polycrystalline piezoelectric ceramic. The ceramic material, or the entire piezoelectric layer, or the entire piezoelectric component, is preferably lead-free.

[0074] Here and below, "lead-free" refers specifically to less than 0.1 percent lead (Pb) by mass, as required by the EU 2011 Restriction of Hazardous Substances (RoHS) Directive.

[0075] In preferred embodiments of the present invention, lead-free means significantly lower lead content or no lead at all.

[0076] The use of lead-free materials in piezoelectric components allows components to be made free of the heavy metal lead, which is harmful to the environment and toxic, enabling new applications, among others, for example in consumer and medical technology products.

[0077] Moreover, the properties of the piezoelectric components described above are very similar to those of conventional piezoelectric components based on lead-containing PZT ceramics, and if the dimensions of the piezoelectric layer of the electrodes and the associated carrier elements are appropriately determined, the piezoelectric components described above can be used in the same way as conventional piezoelectric components.

[0078] The ceramic materials mentioned above are particularly characterized by a high coercive force, which allows the thickness of the piezoelectric layer in piezoelectric components to be reduced without changing other boundary conditions. For example, the amount of material used in the manufacturing process can be reduced by around 30 percent while maintaining the functionality of the component. This reduces production costs and raw material consumption.

[0079] Therefore, the above mentioned polycrystalline ceramic materials are preferably suitable for producing thin polycrystalline piezoelectric layers or thin polycrystalline piezoelectric components.

[0080] Furthermore, since the sintering temperatures of the above-mentioned lead-free ceramic materials are lower than those of conventional lead-containing ceramics, the production of the ceramic layer consumes less energy and can be carried out at low cost.

[0081] The volume and mass of the components are also smaller than lead-containing components, so in addition to the lower sintering temperature, the amount of material that needs to be heated in the sintering furnace is also reduced, resulting in a more economical process, which allows for increased loading, also optimizing space, or for the same loading, a smaller mass needs to be heated to the desired sintering temperature.

[0082] In a preferred embodiment, the composition of the ceramic material is 0.25≦a≦0.40, 0.99≦x≦1.05, and 0.95≦y≦1.005.

[0083] In another preferred embodiment, the composition of the ceramic material is such that 0.28≦a≦0.36, 0.99≦x≦1.05, and 0.975≦y≦1.005.

[0084] Such ceramic materials have particularly favorable properties: They have in particular suitable piezoelectric properties for replacing lead-containing or plastic-containing ceramic layers in different applications, in particular in various thin piezoelectric components.

[0085] The piezoelectric properties considered here primarily include the piezoelectric constant, dielectric constant, electromechanical coupling coefficient, coercive force, Curie temperature, and density of the ceramic material.

[0086] Depending on their composition, lead-free piezoelectric ceramic materials have, in particular, a piezoelectric constant of at least 75 pm / V, a relative dielectric constant of at least 1000, an electromechanical coupling coefficient of at least 0.25, a coercive force of at least 1.8 kV / mm, a Curie temperature of more than 400°C, and a density of at least 7000 kg / m 3 It is preferable that the range is 100 to 2000 nm.

[0087] According to one embodiment, the piezoelectric layer does not contain any plastic as other components, and is preferably made of an inorganic material, in particular a ceramic material.

[0088] Therefore, the piezoelectric layer has high density, high stability, and high strength, which are more pronounced than those of piezoelectric plastic layers.

[0089] According to one embodiment, the piezoelectric layer does not contain any other components than those mentioned above. Preferably, the piezoelectric layer is made of a ceramic material.

[0090] Such a piezoelectric layer has the above-mentioned advantageous properties of ceramic materials and, in particular, is lead-free.

[0091] According to another embodiment, the piezoelectric layer comprises a piezoelectric plastic. The piezoelectric layer may in particular comprise a piezoelectric plastic and a ceramic, preferably one of the ceramic materials mentioned above.

[0092] Plastic-based layers exhibit high flexibility and frequency-dependent deformation, but pure piezoelectric plastics such as PVDF are limited in their applications as actuators / sensors / transducers due to their mechanical and thermal stability.

[0093] The disadvantageous properties of piezoelectric ceramics can be compensated for by combining them in composite materials. For example, sintered piezoelectric ceramic powders or sintered preformed ceramics, e.g. wires, can be added to a plastic matrix. The mechanical, electrical and electromechanical properties of the composite can thus be set by the mixing ratio of the components (i.e. plastic and ceramic) within the range of the properties of the individual components.

[0094] The piezoelectric layer may, for example, be fabricated from a ceramic-plastic composite material and by a manufacturing process such as film stretching or pressing.

[0095] According to one embodiment, the piezoelectric layer has a thickness of at least 40 or at least 50 microns (μm).

[0096] According to one embodiment, the piezoelectric layer has a thickness of up to 150 μm.

[0097] Preferably, the piezoelectric layer has a thickness of at most 140 μm, more preferably at most 130 μm.

[0098] For use as an ultrasonic transducer, the thickness is preferably in the range of 70-130 μm. For tactile applications, the thickness is preferably up to 105 μm.

[0099] Such small layer thicknesses reduce material consumption and costs in the manufacturing process and enable new applications for piezoelectric components.

[0100] According to one embodiment, the corresponding pre-sintered green layer has a layer thickness of at least 50 μm.

[0101] According to one embodiment, the green layer has a thickness of up to 210 μm, preferably in the range of 120 μm to 160 μm.

[0102] For the process of laminating and pressing a plurality of green films to form a green layer, the thickness of each green film is preferably within the range of 30 μm to 130 μm, and particularly preferably 80 μm.

[0103] In particular, by designing such small layer thicknesses for the piezoelectric layers, it is possible to provide lead-free thin piezoelectric components that consume less material during production and less space during installation in the provided application device, which can advantageously provide miniaturized sensors and actuators, for example for incorporation in computing devices, smartphones or for use in automation and automotive applications.

[0104] Such a thin piezoelectric component comprises exactly one piezoelectric layer of the abovementioned layer thickness and electrodes arranged thereon, which preferably also have a small layer thickness of the order of microns.

[0105] Piezoelectric components may be configured for use in a variety of applications.

[0106] Preferably, the entire piezoelectric component can be lead-free, i.e. the component does not contain any lead components outside the piezoelectric layer as well as inside the piezoelectric layer, thus avoiding the use of lead due to its toxic and environmentally harmful properties and complying with legal regulations regarding the avoidance of lead use.

[0107] Preferably, in one embodiment, the piezoelectric component further comprises a carrier element, on which the piezoelectric layer is arranged as described above. The carrier element may be a membrane. The carrier element may be one of the electrodes arranged on the surface of the piezoelectric layer. For example, the piezoelectric element may be connected in a conductive manner (for example by gluing or soldering) on ​​one side to a carrier element having electrical conductivity. In this case, the carrier element is, so to speak, an electrode. Furthermore, the above-mentioned bonding agent may be present between the carrier element and the piezoelectric layer.

[0108] In other embodiments, the piezoelectric element may already have electrodes (e.g. by sputtering a metal layer) which are then connected to the conductive carrier element by conductive connections (as in the previous examples).

[0109] In one embodiment the component comprises a carrier element and a piezoelectric layer. Preferably the piezoelectric layer is embodied as an elliptical or circular plate and is arranged on a carrier element which is also disc-shaped, preferably with a larger surface.

[0110] Preferably, the ratio of the diameter of the circular piezoelectric layer to the diameter of the circular carrier element is in the range of 0.3 to 1.0, preferably in the range of 0.55 to 0.73, more preferably in the range of 0.6 to 0.7, inclusive.

[0111] This allows the interaction between the piezoelectric layer and the carrier element to be optimized for a particular application.

[0112] Alternatively, the disk may have a rectangular shape instead of a circular shape.The surface dimension of the disk-shaped carrier element and the piezoelectric layer is significantly greater than its thickness.

[0113] A first electrode as a thin film is arranged on the surface of the piezoelectric layer remote from the carrier element. In this case, the carrier element may be the second electrode. Alternatively, the second electrode as a thin film may be provided between the piezoelectric layer and the carrier element. A thin film of a connecting material, such as glue or solder, may further be provided between the electrode and the carrier element. Alternatively, the connecting layer may refer to a metal layer manufactured by transient liquid phase sintering, silver sintering or similar processes.

[0114] In one embodiment, the dimensions of the individual component layers are on the same order as the dimensions of the piezoelectric layer, preferably on the order of microns.

[0115] The piezoelectric component is preferably a thin polycrystalline component. The direction in which the layers of the component are stacked vertically is called the stacking direction. The thickness of the component including the above layers in the stacking direction is preferably on the order of microns.

[0116] In a preferred embodiment, the piezoelectric component comprises exactly one piezoelectric layer. Preferably, the piezoelectric component comprises exactly one layer sequence consisting of the above-mentioned first electrode, the piezoelectric layer, the second electrode, the preferred form of which is a carrier element, and optionally a carrier element. The component preferably does not comprise any other layers. The piezoelectric component is therefore designed to be as thin as possible.

[0117] In various embodiments, the piezoelectric component may be specifically designed as a component for use as a tactile actuator, a tactile sensor, a buzzer, an ultrasonic transducer, an ultrasonic transmitter or receiver, a micropump for fluids, an energy harvester, or a particle detector, examples of such embodiments are described in more detail below.

[0118] In one embodiment, the piezoelectric component may be specifically designed for use as a tactile actuator suitable for generating mechanical deformation of a carrier element from an electrical signal applied to a piezoelectric layer.

[0119] By properly tuning the electronic controls with high coercivity, especially the higher coercivity of lead-free ceramics over lead-containing ceramics, the thickness of the piezoelectric layers and components can be reduced without compromising the quality of the tactile signal.

[0120] With corresponding control, the displacement of a piezoelectric actuator with a thin piezoelectric layer with high coercivity is the same as that of an actuator with a thick piezoelectric layer with low coercivity. The coercivity of the piezoelectric layer is in the range of 1.5 kV / mm to 10 kV / mm.

[0121] Due to its high coercivity, the piezoelectric layer is particularly suitable for application of a DC voltage of at least 50 volts and a peak-to-peak voltage of at least 700 volts.

[0122] Thus, lead-free ceramic piezoelectric layers have a higher coercivity than lead-containing ceramics, allowing functionally equivalent thinner and therefore space-saving components to be manufactured while saving material.

[0123] In another embodiment, the piezoelectric component may be specifically designed for use as a tactile sensor suitable for generating an electrical signal that can be picked up on the piezoelectric layer from a mechanical deformation of the carrier element. The component may be implemented for use as a tactile actuator and sensor.

[0124] By properly tuning the electronic analysis instrument with the high coercivity of lead-free ceramics, the thickness of the piezoelectric layer and components can be reduced without compromising the quality of the measured electrical signal.

[0125] With proper control, the electrical signal of a piezoelectric sensor with a thin piezoelectric layer with high coercivity can be the same as that of a sensor with a thick piezoelectric layer with low coercivity. The coercivity of the piezoelectric layer is in the range of 1.5 kV / mm to 10 kV / mm.

[0126] The high coercivity of the piezoelectric layer therefore allows functionally equivalent thinner, and therefore space-saving, components to be manufactured whilst saving material.

[0127] In another embodiment, the piezoelectric component is designed for use as a buzzer.

[0128] Here, a buzzer is an actuator that generates sound from an electrical signal, and is similar to an audio transmitter.

[0129] A buzzer is essentially a tactile actuator that deforms at a specific frequency to produce sound waves in the audible range.

[0130] Here, for example, a minimum requirement can be defined that the sound pressure at a position 10 cm away from the outside of the buzzer membrane is at least 75 decibels. Due to the high coercivity of the lead-free piezoelectric layer, a small thickness of the piezoelectric layer of up to 120 μm is sufficient to generate the desired sound pressure with appropriate control. Preferably, the layer thickness is in the range of 80 μm to 120 μm, more preferably up to 105 μm, more preferably up to 100 μm or less.

[0131] In this case, the thickness of the membrane is preferably within the range of 25 μm to 125 μm.

[0132] Preferably, the layer has a diameter of at least 5 mm and at most 14 mm.

[0133] With these dimensions, the buzzer can cover a frequency range of at least 2 kHz to 8 kHz.

[0134] The high coercivity of the piezoelectric layer therefore allows functionally equivalent thinner, and therefore space-saving, components to be manufactured whilst saving material.

[0135] The piezoelectric layer is specifically designed so that the buzzer reaches a maximum sound pressure when excited by an electrical signal having a voltage of up to 3 volts and an electrical frequency of 4 kHz.

[0136] In another embodiment, the piezoelectric component is designed to be used as an ultrasonic transducer, or an ultrasonic transmitter, or an ultrasonic receiver.

[0137] The ultrasonic transducer may be one that generates ultrasonic waves from an electrical signal (ultrasonic transmitter), or conversely, one that generates an electrical signal from ultrasonic waves (ultrasonic receiver).

[0138] An ultrasonic transducer essentially refers to a tactile actuator or sensor that deforms at a specific frequency to generate or detect sound waves in the ultrasonic range. Such ultrasonic transducers are typically used for distance measurement. In addition, ultrasonic transducers can be used for other applications, such as the transmission of energy and / or data, especially through metals.

[0139] Here, one may define a minimum requirement as a sound pressure high enough to detect objects at a distance of 200 cm or less.

[0140] Due to the high coercivity of the lead-free piezoelectric layer, a piezoelectric layer with a thickness as small as 70 μm to 130 μm is sufficient to generate the desired sound pressure with proper control. Preferably, the diameter of the layer is 5 mm to 14 mm or 5 mm to 7 mm.

[0141] For example, the piezoelectric layer preferably has the following properties: When an AC voltage of 1 volt and a frequency of 1 kHz is applied, the capacitance C of the piezoelectric layer is in the range of 0.9 nF to 1.0 nF. The dielectric loss δ is in the range of 0.05 to 0.15, and is preferably 0.10. The dielectric constant ε is in the range of 800 to 900. The piezoelectric constant d33 is in the range of 100 pC / N to 200 pC / N. The effective coupling coefficient k eff is in the range of 0.2 to 0.3.

[0142] The natural frequency of the piezoelectric layer is, for example, within the range of 450 kHz to 550 kHz, and is preferably 500 kHz.

[0143] At an AC voltage of 0.1 V and the resonant frequency of the ceramic, the capacitance C is, for example, in the range of 0.5 nF to 0.7 nF. In this case, the dielectric constant ε is in the range of 400 to 500.

[0144] In another embodiment, the piezoelectric component is designed as a micropump for a fluid. In such a micropump, a number of haptic actuators are used, which form the lid of a microchamber capable of containing a fluid.

[0145] The deformation of such a haptic actuator can force fluid out of the microchamber, generating a pumping action.The use of advantageous components with thin piezoelectric layers as described above allows the dimensions of the micropump to be reduced, optimizing the material consumption in the manufacture of the micropump.

[0146] In another embodiment, the piezoelectric component is designed for use as a particle detector.

[0147] For this purpose, the piezoelectric component is provided in a flow passage, in which, for example, a gas carrying solid particles can be transported.

[0148] In operation, frequencies in the ultrasonic range excite the piezoelectric layer of the component, causing it to vibrate.

[0149] When a solid particle strikes the membrane of a piezoelectric component, it deforms the piezoelectric layer bonded to it, inducing a change in oscillation frequency that depends on the size and number of the particles and can be determined by electronic analysis equipment.

[0150] When using the advantageous components with thin piezoelectric layers described above, the dimensions of the particle detector can be reduced and the material consumption in the manufacture of the particle detector can be optimized.

[0151] In the applications described above, the piezoelectric components can replace conventional piezoelectric components, including lead-containing piezoelectric materials and / or plastic-containing piezoelectric materials, without compromising functionality.

[0152] The invention further relates to a method for manufacturing a piezoelectric component with a piezoelectric layer, which may have all the features of the component described above.

[0153] Conversely, the features described below also apply to all of the above-described embodiments.

[0154] The method includes several steps. One step includes providing green films. The green films are preferably produced by film stretching. This results in very uniform yet thin films. The thickness of each film is preferably up to 80 μm.

[0155] Another step involves stacking the green films vertically to form a green layer with a preferred layer thickness of up to 130 μm.

[0156] Alternatively, thick green films can be provided one at a time by film casting, a manufacturing process that results in thicker but less uniform films, longer drying times, and generally higher sintering shrinkage.

[0157] A further step involves sintering the green layer at a temperature of up to 1030° C. to obtain the piezoelectric layer.

[0158] In a separate step, the piezoelectric layer is placed on the carrier element and connected to the carrier element by means of material bonding to mechanically couple the layer to the carrier element, whereby the ratio of the thickness of the piezoelectric layer to the thickness of the carrier element is preferably between 0.127 and 1.3.

[0159] Preferably, these steps are performed in the above order, and most preferably, these steps are performed consecutively.

[0160] In one embodiment, a green film is provided. The green film has a structure comprising: (Bi x FeO 3 ) 1-a (Ba y TiO 3 ) a wherein 0.20≦a≦0.50, 0.90≦x≦1.10, and 0.90≦y≦1.01.

[0161] The layer thickness is preferably within the range of 50 microns to 150 microns. Preferably, there is no other layer between each pair of piezoelectric films, and the green films are directly laminated vertically.

[0162] In one embodiment of the method, the green layer is placed on a carrier element before sintering and sintered together with the carrier element. Due to the low sintering temperature, the method is also suitable for carrier elements that cannot be processed at temperatures above 1030° C.

[0163] The production of layers by the above-mentioned film technology allows the production of layers with the desired layer thickness, material savings due to the elimination of cutting processes, and the low sintering temperatures allow the process to be optimized energetically.

[0164] In a preferred embodiment of the method, the sintering temperature is maintained for a maximum of 4 hours.

[0165] In a preferred embodiment of the method the sintering temperature is up to 1000° C. This makes it possible, for example, to reduce the energy consumption and costs of the method and to increase the environmental friendliness of the method.

[0166] In one embodiment of the method, the green layer is placed on a carrier element before sintering and sintered together with the carrier element. Due to the low sintering temperature, the method is also suitable for carrier elements that cannot be processed at temperatures above 1000° C.

[0167] In a preferred embodiment of the method, the sintering temperature is at least 900°C.

[0168] In a further method step, electrodes may be disposed on the piezoelectric layer, preferably on two opposing surfaces of the layer, for example the electrodes may be printed.

[0169] In one embodiment, the piezoelectric layer may be arranged on a carrier element, e.g. a membrane, and mechanically coupled to the carrier element, where the component is preferably designed such that both the carrier element and the piezoelectric layer deform when excited.

[0170] The excitation may specifically include applying an electric field to the piezoelectric layer.

[0171] The carrier element may be one of the electrodes. However, the carrier element may also be provided in addition to the electrodes. In particular, both the piezoelectric layer and the arranged electrodes may be arranged on the carrier element.

[0172] The carrier element and the piezoelectric layer may be connected in the manner of a material bond by co-sintering.

[0173] The piezoelectric layer may be connected to the carrier element in the manner of a material bond, for example by a connecting layer. The connecting layer may comprise an adhesive. The thickness of the connecting layer preferably does not exceed 20 μm.

[0174] The invention further relates to a method for producing a lead-free piezoelectric component with a piezoelectric layer as described above, in which the piezoelectric layer is arranged on a carrier element and connected to the carrier element in the manner of a material bond, thereby mechanically coupling said layer to the carrier element.

[0175] In particular, the green layer may be arranged on a carrier element before sintering and sintered together with the carrier element.All previously described embodiments and their advantageous features are equally applicable to said method.

[0176] Due to the low sintering temperatures, the method is also particularly suitable for carrier elements which cannot be processed at high temperatures. [Brief description of the drawings]

[0177] The following examples are described with reference to the drawings, but the invention is not limited to the examples shown.

[0178] [Figure 1] FIG. 1 is a perspective view of a first embodiment of a piezoelectric component. [Diagram 2] FIG. 2 is a cross-sectional detail of a first embodiment of the piezoelectric component. [Diagram 3] FIG. 2 is a cross-sectional view of a second embodiment of a piezoelectric component as a tactile element. [Figure 4] FIG. 4 is a perspective view of a fourth embodiment of a piezoelectric component as a buzzer or ultrasonic transducer. [Diagram 5] 1 is a schematic diagram of the technical principle of a micropump for fluids; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0179] 1 and 2 show an exemplary first piezoelectric component 1 .

[0180] On the membrane 2 as carrier element, a piezoelectric element is arranged which in turn comprises a first electrode 3, a piezoceramic layer 4 and a second electrode 5. The piezoelectric component 1 and the layers contained therein are embodied in the exemplary embodiment as a circular or elliptical disk.

[0181] Membrane 2 is preferably electrically conductive and comprises a conductive material, for example a metal such as brass, aluminum, titanium, copper or steel, a carbon fiber material, etc. Alternatively, membrane 2 may comprise a plastic material with a metallized surface or containing conductive particles.

[0182] The membrane 2 must be designed to deform in response to the deformation of the ceramic layer 4 .

[0183] The membrane 2 preferably has a greater thickness and diameter than the electrodes 3 , 5 and the piezoelectric ceramic layer 4 .

[0184] The piezoelectric element is attached to the membrane 2 by a connecting material 6, for example an adhesive.

[0185] The piezoelectric ceramic layer 3 is lead-free and is made of (Bix FeO 3 ) 1-a (Ba y TiO 3 ) a These indices are selected from the ranges 0.28≦a≦0.36, 0.99≦x≦1.05 and 0.975≦y≦1.005, for example a=0.305, x=1.030, y=0.995.

[0186] The piezoelectric ceramic layer 4 must be designed so as to deform in response to the deformation of the membrane 2 .

[0187] Preferably, the piezoelectric component 1 is provided with exactly one ceramic layer 4 .

[0188] The lead-free ceramic layer 4 has a much higher coercive force than conventional piezoelectric ceramic layers. For example, the coercive force E c = 1.9 kV / mm.

[0189] Due to the high coercivity, the piezoelectric component 1 has a ceramic layer 4 with a thickness that is significantly smaller than that of conventional components, for example between 50 microns and 110 microns.

[0190] The production of the ceramic layer 4 according to the invention therefore saves material compared to the production of conventional ceramic layers.

[0191] The ceramic material is sintered in an air atmosphere. Due to the relatively low sintering temperature and the relatively short maintenance time, the production of the ceramic is more energy-saving than the production of conventional ceramic layers.

[0192] The above ceramic materials have a relatively high Curie temperature of 450°C and a density of 7.4 × 10 compared to conventional non-lead-free piezoelectric materials. 3 kg / m 3 is equivalent to

[0193] The piezoelectric component 1 may be implemented as a tactile element.

[0194] In one embodiment, the tactile elements may be implemented as actuators that convert electrical signals into mechanical displacements of the membrane 2 .

[0195] For this purpose, an electric field is applied to the piezoelectric ceramic layer 4. The piezoelectric layer deforms in response to the applied electric field. The piezoelectric ceramic layer 4, implemented as a disk, deflects in particular from a neutral position at its center, where the neutral position refers to the position of the ceramic layer 4 when no electric field is applied.

[0196] In another embodiment, the tactile element may be implemented as a touch sensor.

[0197] For this purpose, for example, an additional cover 7 is arranged on the piezoelectric element, as shown in Figure 3. The cover 7 may for example be glued to the piezoelectric element.

[0198] The touch sensor may in particular be mounted in the track pad of, for example, a laptop computer, with the piezoelectric component 1 mounted directly beneath the touch-sensitive surface of the track pad.

[0199] In this case, when pressure is applied to the touch sensitive surface of the track pad (which in this case may be considered as a cover 7 on the piezoelectric element), the piezoelectric element disposed underneath also deforms, and in response to the deformation, a voltage is generated in the piezoelectric layer 4, which is further transmitted as an electrical signal to the electronic analysis instrument.

[0200] Similar touch sensors are also found on the back of mobile phone screens, for example.

[0201] In another embodiment, as shown in Fig. 4, the piezoelectric component 1 can be implemented as a buzzer 10. The technical principle of the buzzer 10 basically corresponds to a tactile element. By applying a suitable and correspondingly high electrical frequency, a rapid and regular deformation of the piezoelectric element is caused, which excites the membrane 2 coupled to it to vibrate. A resonant chamber 11 surrounding the piezoelectric component 1 is suitable for amplifying the acoustic signal thus generated.

[0202] The resonant chamber 11 may for example be an aluminium plug to which the piezoelectric component 1 is glued.

[0203] For example, a voltage of up to 3 volts and an electrical frequency of 4000 Hz may be applied to the piezoelectric layer 4 to generate an acoustic signal of at least 75 decibels.

[0204] In another embodiment, the piezoelectric component 1 is implemented as an ultrasonic transducer 10. The ultrasonic transducer 10 is essentially constructed similarly to the buzzer 10. However, unlike the buzzer, the frequency of the sound generated is in the ultrasonic range rather than the audible range.

[0205] Furthermore, the piezoelectric component 1 as an ultrasonic transducer 10 not only functions as an actuator for generating ultrasonic waves, but also as a sensor for detecting ultrasonic signals. In particular, a reflected ultrasonic signal of the generated and emitted ultrasonic signal can be detected. From the time between the emission and detection of the reflected ultrasonic signal, the distance to the reflecting object can be determined. Thus, such an ultrasonic transducer can be used as a distance sensor, for example in automotive applications.

[0206] In another embodiment shown in FIG. 5, the piezoelectric component 1 is used as an actuator of a micropump 20 for fluids. At least two piezoelectric components 1 are required for the construction of the pump. Here, the piezoelectric components 1 form the cover of interconnected chambers 21. The chambers 21 are connected, for example, by a pipeline 22 suitable for transporting a fluid. The flow direction of the fluid is predefined by a valve 23 in the pipeline. The chambers 21 can generate a stroke by increasing or decreasing their volume due to the deformation of the piezoelectric element. For example, the transported fluid can be made to flow from the first chamber 21 to the second chamber 21 by decreasing the volume of the first chamber 21 and increasing the volume of the second chamber 21 following along the pipeline.

[0207] Such a micropump 20 may be used, for example, for the metering of fluids in the medical field.

[0208] In another embodiment, the piezoelectric component 1 is used as a synthetic jet actuator, i.e. an actuator for generating artificial jets, the principle being the same as for its application as a micropump 20. Such an actuator can be used for example for targeted cleaning of sensitive surfaces, such as the transmission surface of an optical sensing surface.

[0209] In another embodiment, the piezoelectric component 1 can be used as a particle detector. For this purpose, the piezoelectric component 1 is arranged in a flow passage. For example, a gas carrying solid particles can be transported in the flow passage.

[0210] In operation, frequencies in the ultrasonic range excite the piezoelectric layer 4 of the component, causing it to vibrate.

[0211] When solid particles impinge on the membrane 2 of the piezoelectric component 1, the piezoelectric layer 4 bonded to it is deformed, causing a change in the oscillation frequency that depends on the size and number of the particles and can be determined by electronic analysis equipment.

[0212] In another embodiment, the piezoelectric component is used as a transducer to convert mechanical energy into electrical energy, i.e. for "energy harvesting". This application therefore uses the opposite effect to haptic actuators: deformation of the piezoelectric layer 4 generates an electrical potential that can be tapped by an appropriate circuit and temporarily stored as electrical energy, read as a measurement variable, or used to transmit a signal directly.

[0213] Exemplary applications include wireless sensors for light switches, footstep or closure detectors, vibration detectors, and flow detectors.

[0214] In another embodiment, the piezoelectric component 1 described above can be used for the transmission of energy and data through solids by ultrasonic transmission. Such communication is used for controlling and reading sensors, actuators, or electronic identification. One piezoelectric component 1 is used as an ultrasonic transmitter and another piezoelectric component is used as an ultrasonic receiver.

[0215] In an alternative embodiment, different from the previous example, the piezoelectric layer 4 may comprise a piezoelectric plastic, for example PVDF (Polyvinylidene fluoride). The layer may also comprise a ceramic material and a plastic. [Explanation of symbols]

[0216] 1 Piezoelectric Components 2. Membrane 3 electrodes 4 Piezoelectric layer 5 electrodes 6 Connecting materials 7 Cover 10 Buzzer, ultrasonic transducer 11 Resonance chamber 20 Micropump 21 Chamber 22 Pipeline 23 Valve

Claims

1. 1. A piezoelectric component (1), comprising: a piezoelectric layer (4) having a polycrystalline piezoelectric ceramic material with a coercive force of at least 1.8 kV / mm; and a carrier element (2) on which the piezoelectric layer (4) is arranged and mechanically coupled to the piezoelectric layer (4).

2. The piezoelectric component (1) according to claim 1, wherein the piezoelectric ceramic material has an electromechanical coupling coefficient k31 of 0.2 to 0.

3.

3. The dielectric constant ε of the piezoelectric ceramic material r 3. The piezoelectric component (1) according to claim 1, wherein:

4. The dielectric constant ε of the piezoelectric ceramic material r The piezoelectric component (1) according to claim 3, wherein M is in the range of 900-1000, preferably in the range of 910-950.

5. The piezoelectric component (1) according to any one of the preceding claims, wherein the piezoelectric ceramic material has a piezoelectric constant d31 of at least 50 pm / V and at most 100 pm / V.

6. The piezoelectric component (1) according to any one of the preceding claims, wherein the Curie temperature of the piezoelectric ceramic material is in the range of 400°C to 500°C.

7. The piezoelectric component (1) according to any one of the preceding claims, wherein the mechanical quality Qm of the piezoelectric ceramic material is in the range of 50-100.

8. The density of the piezoelectric ceramic material is 7000 kg / m 3 ~7500kg / m 3 A piezoelectric component (1) according to any one of claims 1 to 7, in the range

9. The coercive force, electromechanical coupling coefficient k31, and dielectric constant coefficient ε of the piezoelectric layer (4) r , the piezoelectric constant d31, the Curie temperature, the mechanical quality Qm, the density, or some of the aforementioned variables correspond to corresponding variables of the polycrystalline piezoelectric ceramic material.

10. Piezoelectric component (1) according to any one of the preceding claims, wherein the modulus of elasticity E of the carrier element (2) is in the range of 0.1 Gpa to 1000 Gpa.

11. The piezoelectric layer (4) is made of (Bi x FeO 3 ) 1-a (Ba y TiO 3 ) a 11. The piezoelectric component (1) according to any one of the preceding claims, comprising a ceramic material having a composition: where 0.20≦a≦0.50, and 0.90≦x≦1.10, and 0.90≦y≦1.

01.

12. The piezoelectric component (1) according to any one of the preceding claims, wherein the thickness of the piezoelectric layer (4) is at least 40 μm, and the ratio of the thickness of the piezoelectric layer (4) to the thickness of the carrier element (2) is preferably between 0.127 and 1.

3.

13. The piezoelectric component (1) according to any one of claims 1 to 12, wherein the piezoelectric layer (4) and the carrier element (2) are each disk-shaped, and the ratio of the diameter of the piezoelectric layer (4) to the diameter of the carrier element (2) is preferably 0.55 to 0.

73.

14. A piezoelectric component (1) according to any one of claims 1 to 13, wherein the neutral phase of a composite component consisting of a carrier element (2) and a piezoelectric layer (4) is located within the piezoelectric layer (4), where the neutral phase refers to an imaginary line in which there is no deformation.

15. A piezoelectric component (1) according to any one of the preceding claims, comprising exactly one said piezoelectric layer (4).

16. 16. A piezoelectric component (1) according to any one of the preceding claims, designed to be used as a tactile actuator suitable for generating a mechanical deformation of the carrier element (2) from an electrical signal applied to the piezoelectric layer (4).

17. 17. The piezoelectric component (1) according to claim 16, wherein the piezoelectric layer (4) is suitable for being subjected to a DC voltage of at least 50 Volts and a peak-to-peak voltage of at least 700 Volts.

18. 18. A piezoelectric component (1) according to any one of the preceding claims, designed to be used as a tactile sensor suitable for generating an electrical signal that can be picked up on the piezoelectric layer (4) from a mechanical deformation of the carrier element (2).

19. 16. A piezoelectric component (1) according to any one of claims 1 to 15, designed to be used as a buzzer (10) suitable for converting a periodic electrical signal applied to the piezoelectric layer (4) into a mechanical vibration of the carrier element (2) in the audible range.

20. The piezoelectric layer (4) has a maximum voltage of 3 volts and an electrical frequency of 4.0×10 3 20. The piezoelectric component (1) of claim 19, wherein the buzzer (10) is designed to reach a maximum sound pressure when excited by an electrical signal in Hertz.

21. A piezoelectric component (1) according to any one of claims 1 to 15, designed to be used as an ultrasonic transducer (10) suitable for converting a periodic electrical signal applied to the piezoelectric layer (4) into a mechanical vibration of the carrier element (2) in the ultrasonic range, or vice versa.

22. A piezoelectric component (1) according to any one of the preceding claims, designed for use as a micropump (20) for fluids.

23. A piezoelectric component (1) according to any one of the preceding claims, designed for use as a particle detector.

24. Piezoelectric component (1) according to any one of the preceding claims, wherein the carrier element (2) is electrically conductive and is an electrode (3) arranged on a surface of the piezoelectric layer (4).

25. The piezoelectric component (1) according to any one of the preceding claims, wherein the carrier element (2) is materially connected to the piezoelectric layer (4) by soldering, fusion welding, gluing with an adhesive material or by co-sintering.

26. 26. The piezoelectric component (1) according to claim 25, wherein the adhesive material is non-conductive, or anisotropically conductive, or conductive.

27. The piezoelectric component (1) according to any one of the preceding claims, wherein the piezoelectric component is a radial oscillator and the ratio of diameter to thickness of the piezoelectric layer (4) is at least 10 or more.

28. The piezoelectric component (1) according to any one of the preceding claims, wherein the piezoelectric layer (4) comprises a piezoelectric plastic.

29. 29. The piezoelectric component (1) according to claim 28, wherein the piezoelectric layer (4) comprises polyvinylidene fluoride.

30. 30. Piezoelectric component (1) according to claim 28 or 29, wherein the piezoelectric layer (4) comprises a composite material made of piezoelectric ceramics and piezoelectric plastics.

31. Piezoelectric component (1) according to any one of claims 28 to 30, wherein the coercivity of the piezoelectric layer (4) is at most 125 kV / mm.

32. The dielectric constant ε of the piezoelectric layer (4) r The piezoelectric component (1) according to any one of claims 28 to 31, wherein is greater than 8.

33. Piezoelectric component (1) according to any of the preceding claims, wherein the ratio of the modulus of elasticity of the carrier element (2) to the modulus of elasticity of the piezoelectric layer (4) is in the range of 0.0004 to 3000.

34. A method for manufacturing a piezoelectric component (1) comprising a piezoelectric layer (4), comprising the steps of: Providing at least one green film having a layer thickness of at least 50 μm and at most 150 μm to produce a green layer; sintering the green layer at a temperature of up to 1050° C. to obtain the piezoelectric layer (4); - arranging said piezoelectric layer (4) on a carrier element (2) and connecting said layer (4) to said carrier element (2) in the manner of a material bond such that said layer (4) and said carrier element (2) are mechanically coupled; A method comprising:

35. 35. The method of claim 34, wherein the sintering temperature is maintained for up to 4 hours.

36. 36. A method according to claim 34 or 35, wherein the sintering temperature is up to 1000°C, preferably at least 900°C.

37. The method according to any one of claims 34 to 36, wherein the green layer is arranged on a carrier element (2) before sintering and sintered together with the carrier element (2).

38. The method according to any one of claims 34 to 37, wherein a plurality of said green films are vertically stacked and pressed to produce said green layer.

39. A method according to any one of claims 34 to 38, wherein the sintered layer is poled with an external electric field to obtain the piezoelectric layer (4).

40. The method according to any one of claims 34 to 39, wherein the carrier element and the piezoelectric layer are materially connected by an adhesive layer, a solder layer or a metal layer.

41. 41. The method of claim 40, wherein the adhesive layer is non-conductive, or anisotropically conductive, or conductive.

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