Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/50—Piezoelectric or electrostrictive devices having a stacked or multilayer structure
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/80—Constructional details
  • H10N30/85—Piezoelectric or electrostrictive active materials
  • H10N30/853—Ceramic compositions
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/42—Piezoelectric device making

Definitions

• a piezoelectric component with an actuator body wherein the actuator body has a predetermined breaking point, which is designed such that a crack permitted by the predetermined breaking point divides the actuator body into at least two partial stacks.
• An object to be solved is to provide a piezoelectric multilayer component which remains functional under permanent mechanical stress.
• a piezoelectric multilayer component with a stack of piezoceramic layers and electrode layers arranged alternately one above the other is specified, wherein adjacent layers of the stack are under mutual, inclined in the lateral direction of mechanical stress.
• the layers of the stack are accordingly braced against each other, wherein the stresses or the clamping forces are perpendicular to the stacking direction.
• the mutual tension be present between adjacent piezoceramic layers.
• it can also arise between adjacent piezoceramic layers and electrode layers.
• the multilayer component can form cracks under certain mechanical loads during its operation, which run substantially parallel to the layers.
• the stack may be partly split in the lateral direction or it may burst in the lateral direction due to the existing mechanical stresses along at least one plane between the adjacent layers.
• adjacent layers begin to separate from one another, they slip away from each other in a substantially lateral direction.
• Such a piezoelectric multilayer component is associated with a reduced risk that cracks or gaps run uncontrolled and perpendicular to the layers and thus, for example, short circuits between electrode layers of the multilayer component arise. As a result, the multilayer component can remain functional for a prolonged period under continuous load.
• adjacent layers of the stack have, for example, different sintering shrinkage properties.
• the desired mechanical stress arises between the layers due to the different sintering shrinkage properties of the layers.
• different layers of the stator pels different sintering shrinkage properties.
• a first layer could have a higher sintering shrinkage at a first temperature than the adjacent layer at the same temperature.
• Sintered shrinkage is to be understood as meaning the change in the dimensions of a layer in relation to the passage of time. This means that within a time window at a certain temperature, where the time window can be very small, one layer contracts more than another layer. If the dimensions of a layer change due to the sintering shrinkage, this may be a volume change of the layer.
• adjacent piezoceramic layers may have different sintering shrinkage properties.
• Adjacent electrode layers and piezoceramic layers can also be clamped to one another, in which, for example, the electrode layers additionally contain, in addition to an electrically conductive electrode material, a material which has different sintering shrinkage properties than the adjacent piezoceramic layer.
• the adjacent layers have different lateral sintering shrinkage properties. They contract laterally differently during the sintering process.
• a combination of vertical and lateral sintering shrinkage properties also enables the achievement of the desired mechanical stress. It has been found experimentally that also different grain size distributions within the layers or different distributions of the sizes of the grains contained in the layers support the desired effect. These are ceramic grains, which may be contained not only in piezoceramic layers, but also in electrode layers.
• the materials of adjacent layers of the stack have different calcination temperatures. It has been found that this property helps achieve the desired mechanical stress. In particular, it has been observed that different calcination temperatures of the materials of adjacent layers affect their respective sintering shrinkage.
• adjacent layers contain different dopants that assist in achieving the desired mechanical stress between them.
• different dopants affect their respective sintering shrinkage properties.
• adjacent layers may contain different sintering aids.
• the layer could also contain, for example, a material comprising PbO or SnO and, for example, SiO 2 or a solidifiable liquid phase of one of these materials or combinations of materials.
• the ceramic mixtures are prepared with ceramic grains of different sizes. The particle sizes or the diameters of the grains differ from each other preferably several times. Thus, ceramic mixtures are created which have different particle size distributions.
• the ceramic mixtures may contain organic binders for ease of shaping in films, which may later be removed in a debinding process. Furthermore, different dopants or dopant concentrations can be added to the ceramic mixtures, as a result of which the sintering shrinkage properties of the ceramic mixtures can be further influenced.
• the ceramic mixtures are processed into green sheets. These are printed with electrode layers.
• a preferred electrode material is copper; Silver and palladium or an alloy of at least two of these materials can also be used as electrode material.
• the green sheets are then trimmed and stacked so that adjacent layers of the stack have different grain size distributions.
• a so prepared, still green multi-layer component is then debinded, wherein in the green sheets still existing binder is volatilized or the green sheets are decarburized.
• the multilayer component can be sintered to form a monolithic component.
• the layers of the multilayer component have different sintering shrinkage properties. Thus, they contract to varying degrees during the sintering process. This means that over a sintering period ST, in which, for example, a constant temperature TempO is maintained, the layers contract at different rates, so that this already mechanical stresses can arise.
• a constant temperature TempO is maintained, the layers contract at different rates, so that this already mechanical stresses can arise.
• this process can be further modulated.
• a first layer could lose x% of its pre-sintering volume, while a second adjacent layer could lose y% of its pre-sintered volume.
• ST t 2 + ⁇ t could lose the first layer u% of its pre-sintered volume at another temperature Temp2, while the second adjacent layer could lose w% of its pre-sintered volume.
• the temperatures to which the multilayer component is exposed are controlled in such a way over a sintering period that preferably each layer has reached its desired shape in the sintered and cooled state of the multilayer component, regardless of how it reaches this.
• the shapes or lateral dimensions of the layers of the stack in the final state are comparable with one another in such a way that a multilayer component is produced which has outer surfaces which are as flat as possible. In the case of rectangular layers, for example, a parallelepiped stack with flat side surfaces should arise.
• FIG. 1 shows a piezoelectric multilayer component
• FIG. 2 shows the sintering shrinkage of different ceramic mixtures as a function of temperature
• FIG. 3 shows the geometric relationship of adjacent layers at a first temperature
• FIG. 4 shows the geometric relationship and the different sintering shrinkage behavior of adjacent layers at a second temperature
• FIG. 5 shows the geometric relationship and the different sintering shrinkage behavior of adjacent layers at a second temperature.
• FIG. 1 shows a piezoelectric multilayer component 1 with a basic body 2 which comprises a stack of piezoceramic layers 3 and electrode layers 4 arranged one above the other. On two outer surfaces of the main body 2 are longitudinally extending electrical external contacts 5 and 6 are applied, which serve the electrical contacting of the device.
• the electrode layers 3 may contain copper, palladium and / or silver or an alloy of several of these materials.
• Adjacent piezoceramic layers 3 have different sintering shrinkage properties by means of different material compositions M1 and M2. They are piezoceramic Layers 3 alternately stacked, ie in the order Ml, M2, Ml, M2, with different material compositions. For example, it has proved to be favorable if the material compositions of adjacent piezoceramic layers are chosen such that their calcination temperatures differ by between 120 and 80 ° C., in particular around 100 ° C. Additionally or alternatively, the particle sizes or diameters of the piezoceramic grains of adjacent layers could differ by between 1.1 to 1.6 ⁇ m, yet each layer could have its own particle size distribution with a variance of a few tenths of a ⁇ m.
• the grains of a layer M1 could have diameters between 0.4 and 0.6 ⁇ m and the grains of an adjacent layer M2 could have diameters between 1.5 and 2.2 ⁇ m.
• a layer M2 may have a grain size distribution with larger grains than a layer Ml adjacent to it.
• FIG. 2 shows a graph with two curves ml and m2, which in each case represents the temperature-dependent sintering shrinkage property of piezoceramic layers 3 with a material composition M1 or M2.
• the curve ml shows how the lateral dimension 1 of a piezoceramic layer 3 with material composition M1 decreases as a function of increasing temperature.
• Ti a temperature
• T S 2 a maximum sintering shrinkage of the piezoceramic layer 3 with the material composition M1 at temperature T S 2 is achieved.
• T S 2 the change in the lateral dimension 1 in relation to the temperature reaches its peak.
• the curve m2 shows how the lateral dimension 1 of a piezo-ceramic layer 3 with material composition M2 decreases as a function of increasing temperature.
• FIG. 3 shows a stack of schematically illustrated 3 piezoceramic layers before a sintering process.
• the topmost layer and the bottommost layer, as shown, have the same material compositions M2.
• a piezoceramic layer arranged between these layers has a different material composition M1, which differs in its sintering shrinkage properties from that of the adjacent layers.
• the illustration indicates the state of the layers when they are not exposed to a temperature Ti leading to a sintering shrinkage.
• FIG. 4 shows the stack of FIG. 3 at a different temperature T 2 (see also FIG. 2), the layers having the material compositions M 2 having a higher sintering shrinkage than the layer having the material composition M 1 lying between them. Therefore, the layers M2 are shown with a smaller lateral dimension than the layer M1.
• the arrows shown in the layers indicate tensile or compressive loads. Due to the slower sintering shrinkage of the middle layer Ml compared to their adjacent layers have a tensile force on the adjacent layers of material composition M2. This is shown with arrows pointing outwards. The opposite is true for the middle layer: due to the higher sintering shrinkage of its adjacent layers, the middle layer M1 is entrained by it, or an inwardly acting compressive force acts on the middle layer.
• FIG. 5 shows the stack of FIGS. 3 and 4 at a different temperature T 3 (see also FIG. 2), whereby up to this point in time a reverse effect has already occurred compared to FIG. Since the exposure of the stack of the preceding temperature T 2 up to and including the temperature T 3 , the layers with the material compositions M2 have a lower sintering shrinkage than the layer with the material composition M 1 lying between them. Due to the faster sintering shrinkage of the middle layer M1 compared to its adjacent layers, a compressive force acts on the adjacent layers of material composition M2. This is shown with inward pointing arrows.
• the middle layer M1 due to the slower sintering shrinkage of its adjacent layers, the middle layer M1 is slowed down by the layer adjacent to it in its tendency to pull inward, or an outward pressure force acts on the middle layer M1 , Up to a temperature T 3 as explained above, the mutual effects of the different lateral contractions of the layers have resulted in creating a stack which is flat from its outer surface, ie a stack having a uniform contour extending over the height of the stack , However, material-weakened boundary surfaces or boundary regions between the individual layers of the piezoelectric actuator have arisen up to this time, which permit a controlled formation of cracks running parallel to the layers in the case of certain tensile loads of a piezoelectric actuator put into operation.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Fuel-Injection Apparatus (AREA)
• Compositions Of Oxide Ceramics (AREA)
• General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)

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• 2007
  • 2007-05-11 DE DE102007022093A patent/DE102007022093A1/de not_active Withdrawn
• 2008
  • 2008-05-09 EP EP08759507A patent/EP2147469B1/de not_active Not-in-force
  • 2008-05-09 CN CN2008800156671A patent/CN101730944B/zh not_active Expired - Fee Related
  • 2008-05-09 WO PCT/EP2008/055783 patent/WO2008138906A1/de not_active Ceased
  • 2008-05-09 JP JP2010506954A patent/JP5666901B2/ja not_active Expired - Fee Related
• 2009
  • 2009-11-10 US US12/615,579 patent/US7960899B2/en not_active Expired - Fee Related

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