Piezoelectric assembly and method of forming a piezoelectric assembly

Abstract

A piezoelectric assembly comprising: a substrate of nickel, copper, or steel, a first orientation layer assembled on the substrate, and a piezoelectric layer on the orientation layer. The piezoelectric layer has a (100) degree of orientation of 90% or greater with respect to a local surface normal.

Description

[0001] Piezoelectric films and piezoelectric assemblies are used in many applications that utilize the direct or inverse piezoelectric effect.

[0002] For example, piezoelectric assemblies can be used in energy harvesting devices, where electrical energy is generated by the deformation of a piezoelectric active material or piezoelectric layer. Furthermore, piezoelectric assemblies can be applied in tactile detectors, where an electrical signal is generated upon tactile contact. Other examples are micromechanical applications or micromotors, where work is performed by applying a voltage to a piezoelectric element.

[0003] Due to their wide range of applications, there is a demand for inexpensive yet high-performance piezoelectric devices or assemblies. Furthermore, the assemblies should be robust and compatible with flexible applications.

[0004] However, piezoelectric assemblies or layers prior to this invention could not satisfactorily meet this requirement.

[0005] The preparation of crystalline piezoelectric active materials, particularly the solution-based preparation of piezoelectric perovskite materials, is described in detail throughout the literature. For example, a description can be found in US 4,946,710 A.

[0006] Perovskite piezoelectric films are typically formed on silicon wafer substrates. Silicon wafer substrates are expensive because they are usually made of single-crystal materials. Furthermore, silicon wafers are fragile and therefore can only withstand slight bending.

[0007] Nevertheless, piezoelectric layers with high voltage response values ​​have been produced on silicon wafer substrates, such as those disclosed in Non-Patent Document 1.

[0008] For example, high-performance piezoelectric films can be prepared from piezoelectric lead zirconate titanate (PZT) films. These PZT films exhibit the highest piezoelectric response along the direction (100) of the perovskite crystal cell. This means that with d 33 The longitudinal piezoelectric effect, represented by the value, is highest in films with a crystal orientation (100).

[0009] For example, for a PZT film on a flat substrate surface, the orientation (100) of the PZT microcrystals must be highly aligned with the surface normal in order to achieve a high voltage response.

[0010] Applying a seed layer to a substrate beneath the PZT film is a common method for forming highly oriented PZT films. The seed layer is typically a material grown in an orientation defined by synthesis and processing parameters. This defined orientation then serves as a template for the layers grown above. Typically, lanthanum nickelate films, strontium ruthenate films, lead titanate films, or titanium dioxide films have been used to form oriented PZT films.

[0011] The property of these seed layers is that they can be produced on silicon substrates with high quality and highly preferred orientation using solution-based techniques such as sol-gel deposition.

[0012] Due to the limitations of silicon wafer substrates, attempts have been made to fabricate piezoelectric films based on perovskite materials on inexpensive metal substrates, with several examples documented in the literature.

[0013] For example, WO 2017 / 202652 A1 discloses the sol-gel derivatization preparation of a transparent piezoelectric device. A transparent PZT film is deployed on a transparent substrate (e.g., glass or fused silica). A thin, transparent nucleation layer composed of metal oxides such as TiO2, ZrO2, Al2O3, etc., is arranged between the transparent substrate and the transparent PZT layer. Although the PZT film disclosed is crystalline, piezoelectric properties for inexpensive substrates have not been reported. Only the ferroelectric properties and low dielectric loss of the device have been reported.

[0014] For example, EP 1282901 B1 discloses the sol-gel derivatization preparation of PZT films on various metal foils (e.g., brass, platinum, titanium, and stainless steel). The application of a barrier layer between the substrate and the PZT film is reported. Although the PZT film disclosed is crystalline, its piezoelectric properties for inexpensive stainless steel substrates have not been reported. Only a low dielectric constant below 150 at zero DC field strength has been reported.

[0015] For example, WO 2020 / 084066 A1 discloses the inkjet printing derivative preparation of piezoelectric films composed of materials such as PZT, PLZT, and LNO. The PZT film is printed on a noble metal substrate, such as Pt, Au, or Pd, or on a substrate coated with a noble metal, such as platinum-plated silicon, glass, or steel. To avoid undesirable spreading of the piezoelectric film printing ink due to excessive wetting of the noble metal surface of the substrate, a SAM-layer composed of an organothiol (e.g., 1-dodecanethiol) is deployed between the noble metal substrate surface and the printed piezoelectric film. The SAM-layer is no longer present in the final device after heat treatment and is not intended to affect the piezoelectric film at all. Although the disclosed PZT film is crystalline, its piezoelectric properties have not been reported.

[0016] Non-Patent Document 2 describes the formation of a PZT film on a nickel-chromium-based austenitic steel foil, in which a lanthanum nickelate buffer layer is applied. However, the PZT film has a mixed crystallographic orientation.

[0017] Non-Patent Document 3 describes the formation of a PZT film on a hafnium-coated nickel substrate with a preferred orientation (100). The high degree of orientation is achieved by a highly oriented lanthanum nickelate film deposited on the hafnium-coated substrate prior to the formation of the PZT film.

[0018] Besides these methods, there is no known method in which highly oriented perovskite piezoelectric materials are formed on inexpensive metal substrates templated by seed layers of perovskite structures without any additional support layers or structures.

[0019] In addition, the different coefficients of thermal expansion between the piezoelectric perovskite film and the substrate are a problem, which is also important in the case of inexpensive metal substrates.

[0020] During the fabrication of piezoelectric films, this difference in thermal expansion coefficients can lead to high mechanical stress in the piezoelectric film, which may eventually cause the film to rupture or at least reduce the piezoelectric properties due to the clamping effect of the substrate.

[0021] In this context, Non-Patent Document 4 discloses the formation of a porous PZT film on a silicon substrate, which results in stress decoupling due to local elastic relaxation in the film stress.

[0022] However, prior to this application, there have been no reports of using porous structures on inexpensive metal substrates.

[0023] Non-patent literature:

[0024] Non-patent literature 1: Davide Balma, Andrea Mazzalai, Nachiappan Chidambaram, Cosmin S. Sandu, Antonia Neels, Alex Dommann, Peter Hess, Dieter Binz, Paul Muralt; Piezoelectric Longitudinal Coefficients in Sol–gel PZT Thin Film Multilayers Journal of the American Ceramic Society; 2014; Vol. 97; pp. 2069-2075.

[0025] Non-patent literature 2: Sung Sik Won, Hosung Seo, Masami Kawahara, SebastjanGlinsek, Jinkee Lee, Yunseok Kim, Chang Kyu Jeong, Angus I. Kingon, Seung-HyunKim; Flexible vibrational energy harvesting devices using strain-engineered perovskite piezoelectric thin films Nano Energy; 2019; Volume 55; pp. 182-192.

[0026] Non-Patent Literature 3: Hong Goo Yeo, Susan Trolier-McKinstry; {001} Oriented piezoelectric films prepared by chemical solution deposition on Ni foilsJournal of Applied Physics; 2014; Volume 116; Page 014105.

[0027] Non-patent literature 4: Aleksander Matavž, Andraž Bradeško, Tadej Rojac, Barbara Malič, Vid Bobnar; Self-assembled porous ferroelectric thin films with a greatly enhancedzoelectric response Applied Materials Today; 2019; Volume 16; pp. 83-89.

[0028] The aforementioned problems are addressed by the subject matter of claim 1 of this application. Further advantageous embodiments are described in the dependent claims. Furthermore, a method for forming a piezoelectric assembly that solves the aforementioned problems is claimed.

[0029] As a first aspect, a piezoelectric assembly is provided, comprising a base metal substrate having a main substrate surface. A first orientation layer is disposed on the main substrate surface, wherein the first orientation layer comprises a first material with a crystalline perovskite structure, the first material constituting at least 90 wt% of the first orientation layer. Furthermore, a first piezoelectric layer is disposed on the first orientation layer, wherein the first piezoelectric layer comprises a lead-containing piezoelectric material with a crystalline perovskite structure, and the piezoelectric material has a longitudinal piezoelectric coefficient (d) along the direction (100). 33 The first material is greater than the first material of the first orientation layer. The orientation degree o of the crystalline perovskite structure of the first piezoelectric layer is 90% or greater. The orientation degree o is the average alignment between the orientation (100) of the unit cell of the crystalline piezoelectric material and the local surface normal N or the surface of the host substrate.

[0030] This assembly provides a high-performance piezoelectric film based on a lead-containing perovskite material on an inexpensive base metal substrate. Typically, these substrates do not have a preferred crystal orientation; that is, they can be polycrystalline or amorphous. The substrate can be, for example, a foil or sheet of material.

[0031] These bendable or flexible substrates allow for the fabrication of bendable or flexible piezoelectric assemblies, for example, assemblies that can withstand bending of up to 90° over a length of 20 mm.

[0032] The substrate of the assembly can be used as the first electrode, typically together with an orientation layer that can conduct electricity.

[0033] Preferably, the first material of the crystalline perovskite structure constitutes at least 95 wt%, more preferably 99 wt%, of the first orientation layer, and ideally, the first orientation layer is composed entirely of the first material.

[0034] Typically, the first orientation layer contributes little to the overall piezoelectric response of the piezoelectric assembly. For example, the first orientation layer can be piezoelectrically inert.

[0035] However, the first orientation layer can be a seed layer in the device manufacturing process. As a seed layer composed of perovskite material, the first orientation layer can be used as a template to transfer its orientation to the first piezoelectric layer disposed thereon. For example, the first orientation layer can be grown in a preferred orientation (100) for the transfer of perovskite material to the first piezoelectric layer.

[0036] Therefore, introducing a first orientation layer can enhance the piezoelectric response of a piezoelectric assembly by aligning the piezoelectric material with the crystalline perovskite structure of the first piezoelectric layer.

[0037] Furthermore, the first alignment layer can serve as a buffer layer to prevent ion fusion or chemical reactions between the substrate and the first piezoelectric layer. This prevents degradation of the piezoelectric layer due to chemical changes during heating processes (e.g., annealing).

[0038] Here and below, the orientation degree o is defined as the average alignment between the orientation (100) of the perovskite crystallite of the first piezoelectric layer and the local surface normal N of the host substrate surface. The local surface normal N is the surface normal of the tangent plane of the host substrate surface at a certain point on the host substrate surface.

[0039] In one embodiment, the substrate of the piezoelectric assembly has a second surface opposite to the surface of the main substrate, and a layered structure including a piezoelectric layer on an alignment layer is arranged on the surface of the second substrate, similar to a first piezoelectric layer on a first alignment layer assembled on the surface of the main substrate.

[0040] This means that in the case where the substrate is a flat film or sheet, a symmetrical structure is formed, in which the mirror is located between the surfaces of the main substrate and the second substrate.

[0041] When the substrate is uneven, symmetry is usually maintained along the direction of the local surface normal N of the main substrate surface.

[0042] In a further embodiment of the piezoelectric assembly, a second orientation layer comprising a first material with the same crystalline perovskite structure as the first orientation layer is disposed above the first piezoelectric layer. Furthermore, in this embodiment, the second piezoelectric layer is disposed on the second orientation layer, wherein the second piezoelectric layer comprises the same piezoelectric material as the first piezoelectric layer having the same degree of orientation α of 90% or greater.

[0043] This means that the second piezoelectric layer can be identical to the first piezoelectric layer. Typically, the second piezoelectric layer also has at least 90% orientation.

[0044] Arranging an additional piezoelectric layer on the substrate, on a second surface, or above the first piezoelectric layer has the advantage of enhancing the overall piezoelectric strength of the assembly without excessively increasing the thickness of a single piezoelectric layer. During the inverse or direct piezoelectric effect, a relatively thick piezoelectric layer tends to deform strongly.

[0045] Separating the piezoelectric material layer by using a non-piezoelectric active layer (in this case, an orientation layer) can help prevent this strong overall deformation of the device or piezoelectric assembly.

[0046] In such a structure, if the second orientation layer is conductive, the second orientation layer can be used as an internal electrode.

[0047] In principle, an additional layer of metal electrodes can also be arranged between the first piezoelectric layer and the second orientation layer.

[0048] In a further embodiment of the piezoelectric assembly, the first orientation layer includes a porous orientation sublayer having a porous structure with a relative porosity of up to 70%.

[0049] Porosity can be understood as follows: a porous oriented sublayer comprises a first material and pores, and the volume fraction of pores in the porous oriented sublayer can be up to 70%, meaning that up to 70% of the volume of the porous oriented sublayer can be composed of pores. Therefore, this definition can be considered similar to the definition of relative density of porous materials. For example, preferably, the porous oriented sublayer can have a porosity of up to 50%.

[0050] In principle, the entire first orientation layer can be composed of porous orientation sublayers.

[0051] By using porous oriented sublayers, compressive or tensile stresses arising from the different coefficients of thermal expansion between the first piezoelectric layer and the substrate can be compensated. Therefore, the degradation of the piezoelectric effect caused by the substrate clamping effect can be reduced.

[0052] This means that the orientation layer can have the effects of template, buffer, and stress relief.

[0053] In another embodiment of the piezoelectric assembly, the first orientation layer includes at least one dense orientation sublayer in addition to the porous orientation sublayer. In this embodiment, the porous orientation sublayer has a pore concentration that is at least twice that of the dense orientation sublayer.

[0054] In such a configuration, due to its dense morphology, the dense oriented sublayer can serve as an effective buffer to prevent ions from diffusing between the substrate and the first piezoelectric layer.

[0055] Porous oriented sublayers can provide stress relief.

[0056] Typically, dense oriented sublayers do not need to have 100% density, which can be achieved through preparation processes based on solution deposition techniques. However, the density of dense oriented sublayers is usually at least twice that of porous oriented sublayers.

[0057] In a further embodiment of the piezoelectric assembly, at least one dense orientation sublayer is disposed directly on the surface of the main substrate, and a porous orientation sublayer is disposed on the dense orientation sublayer.

[0058] Placing a dense, oriented sublayer directly on the surface of the substrate can prevent ions from diffusing directly from the substrate. Therefore, buffering can be effective.

[0059] In a further embodiment, an additional dense orientation sublayer is arranged on the porous orientation sublayer.

[0060] This means that porous orientation sublayers can be sandwiched between two dense orientation sublayers.

[0061] This offers the added advantage of allowing the dense, closed surface to directly contact the first piezoelectric layer. Therefore, the densely oriented sublayer can serve as an effective template for the first piezoelectric layer.

[0062] If an assembly includes more than one orientation layer, the structure of these additional orientation layers can be similar to that of the first orientation layer.

[0063] In one embodiment of the piezoelectric assembly, the average pore size of the porous orientation sublayer is 100 nm or less.

[0064] A pore size of less than 100 nm allows for the fabrication of a sealing layer on a porous orientation sublayer.

[0065] Preferably, the average pore size can be from 1 nm to 20 nm. In this case, it is more effective to prepare a closed and dense layer above the porous orientation sublayer.

[0066] In a further embodiment of the piezoelectric assembly, the first material is selected from lanthanum nickelate (LaNiO3), strontium ruthenium ruthenium oxide (SrRuO3), and lead titanate (PbTiO3).

[0067] During chemical solution deposition-based manufacturing methods, these materials with high orientation can be prepared based on, for example, the concentration of the coating solution or processing parameters. Therefore, these materials can be effectively used as templates.

[0068] These materials allow for the fabrication of both dense and porous oriented sublayers. Furthermore, they effectively buffer the substrate and the first piezoelectric layer. They also allow for efficient templated orientations, particularly the orientation (100) of the piezoelectric material.

[0069] Among these first-line materials, lanthanum nickelate (LaNiO3) is particularly favored.

[0070] In a further embodiment of the piezoelectric assembly, the first material of the first orientation layer has an orientation degree of at least 90% or greater that is the same as the crystalline perovskite structure of the first piezoelectric layer.

[0071] With an orientation degree of greater than 90%, the first orientation layer can be an effective template that can promote the growth of microcrystals of the piezoelectric layer on the orientation (100), thereby obtaining a piezoelectric material in the first piezoelectric layer with an orientation degree of (100) of 90% or greater.

[0072] Even more advantageous is that the orientation degree of the first material in the first orientation layer is 95% or higher, or even better, 99% or higher.

[0073] In the case of layered orientation layers, typically all sublayers have an orientation degree of 90% or higher.

[0074] In a further embodiment of the piezoelectric assembly, the first orientation layer has a thickness of 10 nm to 500 nm.

[0075] Within this thickness range, the first alignment layer can serve as an effective buffer between the piezoelectric layer and the substrate. For thinner films, especially for thinner porous alignment layers, the buffer may be ineffective.

[0076] Furthermore, films of this thickness can be prepared with a high degree of orientation, and thicknesses within this range can also be effectively prepared using chemical solution deposition techniques.

[0077] Higher thicknesses than those mentioned above may require longer fabrication processes, leading to inefficiencies. Furthermore, film quality may degrade for films exceeding 500 nm in thickness.

[0078] In a further embodiment of the piezoelectric assembly, the substrate is titanium (Ti), aluminum (Al), nickel (Ni), copper (Cu), or preferably steel.

[0079] These materials are inexpensive and allow for the fabrication of the first orientation layer on them.

[0080] Nickel-chromium based austenitic steels are particularly favored as base materials because they are crystalline, inexpensive, and effectively resistant to oxidation. This can be important in the typical material processes for preparing orientation layers, which are usually carried out in an oxygen-containing atmosphere. This also allows for applications in corrosive environments.

[0081] In this sense, nickel-chromium-based austenitic steel is favored, especially over nickel-based or copper-based materials with lower oxygen resistance.

[0082] In addition, nickel-chromium-based austenitic steels are particularly suitable because they have reversible flexibility and bendability.

[0083] In a further embodiment of the piezoelectric assembly, the first piezoelectric layer is composed solely of [Pb] 1-y S 1 y [(Zr x Ti 1-x ) 1-z S 2 z O3 represents the composition of piezoelectric materials, where S 1 It is the first substituent and S 2 It is a second substituent. x is chosen between 0.40 and 0.95. y is less than 0.30, and z is less than 0.15. Preferably, y is less than 0.25. Preferably, at least one of y and z is greater than 0. Even more preferably, y and z are greater than 0.

[0084] In [Pb] 1-y S 1 y [(Zr x Ti 1-x ) 1-z S 2 z In O3, the first substituent S 1 It partially occupies the A-site of the perovskite unit cell (general formula ABO3) and partially substitutes for lead. The second substituent is S. 2 It occupies the B-site of the perovskite unit cell, partially replacing zirconium or titanium ions.

[0085] For example, S 1 It can be one or more selected from Na, K, Ag, Ba, La, Sr, Ca, Nd, Y, Eu, Gd, Tb and Dy.

[0086] For example, S 2 It can be one or more selected from Cu, Ni, Co, Hf, Mg, Mn, Fe, Nb, V and W.

[0087] Lead titanate doped materials are particularly advantageous perovskite piezoelectric materials.

[0088] Especially near quasi-isomorphic phase boundaries, these materials exhibit orders of magnitude higher in dielectric and piezoelectric constants, such as the longitudinal piezoelectric coefficient (d). 33 ).

[0089] Based on the degree of substitution and the properties of the substituents, quasi-isomorphic phase boundaries at room temperature can be identified, where the x value is 0.45 to 0.6, which is a preferred range.

[0090] The y value can preferably be below 0.10, for example below 0.05 or even 0.02 or lower. Particularly advantageous dopants are manganese, niobium or lanthanum.

[0091] According to a further embodiment of the piezoelectric assembly, the first piezoelectric layer may have a thickness of 0.1µm to 5µm.

[0092] This thickness range can be achieved using techniques based on chemical solution deposition.

[0093] As a further aspect, an apparatus including the piezoelectric assembly described above is provided, wherein the piezoelectric assembly is attached to a surface of the apparatus and configured to generate a tactile signal at that surface.

[0094] The described piezoelectric assembly can be advantageously used in devices for detecting tactile signals, such as touchscreen applications.

[0095] As a further aspect, an apparatus including the aforementioned piezoelectric assembly is provided, the apparatus further comprising an energy storage element, wherein the piezoelectric assembly is configured to collect electrical energy generated in the piezoelectric assembly during mechanical deformation of the piezoelectric assembly, and wherein the energy storage element is configured to store the electrical energy collected by the piezoelectric assembly.

[0096] As a further aspect, a micromirror comprising the piezoelectric assembly as described above is provided. The micromirror includes a mirror surface. The mirror surface may be a reflective surface of the piezoelectric assembly. In another embodiment, a mirror having a mirror surface and a back surface opposite the mirror surface is provided, and the piezoelectric assembly is attached to the back surface. In both cases, the piezoelectric assembly is configured to bend the micromirror when a voltage is applied to the piezoelectric assembly.

[0097] In particular, flexible and bendable piezoelectric assemblies are advantageous in such applications because they bend together with a bendable mirror. Therefore, the high precision of the piezoelectric device allows for the use of such micromirror setups to focus or defocus light.

[0098] As another aspect, a method for forming the aforementioned piezoelectric assembly is provided. This method includes providing a base metal substrate having a main substrate surface. Furthermore, the method includes forming a first seed layer on the main substrate surface comprising a first material containing a crystalline perovskite structure represented by the general formula ABO3, which includes depositing a first seed layer solution containing A ions and B ions on the main substrate surface and crystallizing the perovskite structure through a first annealing process. Additionally, the method includes forming a first piezoelectric layer of a lead-containing piezoelectric material containing a crystalline perovskite structure, which includes depositing a piezoelectric layer solution containing lead ions and other ions of the piezoelectric material and crystallizing the lead-containing perovskite structure through a second annealing process.

[0099] For example, lanthanum nickelate can be the first material. In this case, A is La in the ABO3 crystal structure, and B is Ni in the ABO3 crystal structure.

[0100] This chemical solution deposition technique is an easy-to-apply and cost-effective method for forming both seed layers and piezoelectric layers of perovskite.

[0101] Typically, the formation process of a seed layer can include several deposition steps. For example, it can include repeated deposition and annealing of thin sublayers, which together form the first seed layer of crystalline perovskite. The same principle applies to piezoelectric layers.

[0102] Typically, the preparation of the first seed layer and the first piezoelectric layer may further include drying and pyrolysis steps.

[0103] A seed layer with a high degree of orientation o of 90% or higher can be prepared. Therefore, by preparing a first piezoelectric layer on the first seed layer, the orientation seed layer can promote the crystallization of perovskite crystals in the direction (100).

[0104] After the piezoelectric assembly, including this process, is completed, the first seed layer can be identified as the first orientation layer.

[0105] As one embodiment of the method for forming a piezoelectric assembly, a first seed layer can be prepared as a layered structure. This may include the steps of depositing a first seed layer solution containing A ions and B ions and subsequently forming a dense seed layer, the step of forming the dense seed layer including a first pyrolysis process. This first pyrolysis process can be characterized by a first pyrolysis temperature T1 and a first holding time t1 at the first pyrolysis temperature T1. Furthermore, the process includes depositing a second seed layer solution containing A ions and B ions and forming a porous seed layer through a second pyrolysis process. The second pyrolysis process is characterized by a second pyrolysis temperature T2 and a second holding time t2 at the second pyrolysis temperature T2.

[0106] This means that the first seed layer is prepared as a layered structure, and the layered structure includes a dense seed layer and a porous seed layer. The dense seed layer can be prepared by directly depositing the first seed layer solution onto the surface of the host substrate. This means that the dense seed layer is directly prepared on the surface of the host substrate. In this case, a porous seed layer can then be prepared on top of the dense seed layer. Therefore, as described above, the dense oriented seed layer is directly formed on the surface of the host substrate, with the porous oriented seed layer on top. This achieves an effective buffering effect.

[0107] However, in principle, the order can be reversed and a porous crystal seed layer that is in direct contact with the surface of the main substrate can be prepared.

[0108] Furthermore, it can be noted that a pyrolysis procedure is typically applied before the annealing procedure. For example, organic components that may be present in the seed layer solution are at least partially removed by the pyrolysis procedure. Thus, an amorphous primary seed layer can be formed. During annealing, the material can crystallize and a crystalline seed layer can be formed.

[0109] As a further aspect of the method of forming a piezoelectric assembly, the following relationship can be defined: T2 is less than T1 and / or t2 is less than t1.

[0110] In cases where the second pyrolysis temperature T2 is lower than the first pyrolysis temperature T1, organic components that may typically be present in the second seed layer solution tend to not completely decompose and dissipate completely from the formed layer. Thus, partially solid but mainly gaseous residues can result in a porous seed layer having a higher porosity than a dense seed layer.

[0111] A pyrolysis hold time t2 that is shorter than t1 can have a similar effect. The mere short flash for the hold time t2 at the second pyrolysis temperature T2 results in a less efficient dissipation and removal of residues and decomposition products of the organic components than at the relatively longer first hold time t1.

[0112] In cases where t2 < t1, T1 and T2 can be the same, which can support a less refined process management than in cases where T1 and T2 are set to different values.

[0113] If simultaneously T2 < T1 and t2 < t1, the effect can be increased and the porosity of the porous seed layer can be increased compared to a dense seed layer.

[0114] Both the dense seed layer and the porous seed layer can be formed by repeated deposition, drying, pyrolysis, and annealing cycles in order to achieve the desired thickness of the sublayer or the entire first seed layer.

[0115] In a further embodiment of the method of forming a piezoelectric assembly, the second seed layer solution can contain a polymer. Furthermore, a second pyrolysis procedure can be carried out to incompletely decompose and dissipate the polymer.

[0116] Typically, the polymer can be regarded as an organic component that is more difficult to decompose than other smaller organic molecules that are typically present in the seed layer solution.

[0117] This method allows for the formation of a porous seed layer even if the first pyrolysis procedure and the second annealing procedure are the same.

[0118] When forming a porous seed layer from a second seed layer solution containing a polymer, two effects can lead to the formation of pores. First, the polymer preoccupies space, which can become pores after pyrolysis and annealing. Second, and perhaps more importantly, in the second annealing process, gaseous decomposition products can be formed from the polymer, which are trapped in the formed porous seed layer and can thus form pores.

[0119] Generally, using a solution containing a polymer supports the formation of a porous seed layer with a higher porosity than in the absence of a polymer.

[0120] However, an even higher porosity can be achieved by additionally having T2 < T1 and / or t2 < t1.

[0121] Generally, if the second pyrolysis temperature is too high and / or the second holding time is too long, complete decomposition and dissipation of the polymer can occur, which typically inhibits pore formation.

[0122] In one embodiment of the method for forming a piezoelectric assembly, at least the first seed layer solution or the piezoelectric layer solution is deposited by a spin coating method.

[0123] The spin coating method is a routinely applied technique by which various substrates can be easily coated with a perovskite film. They allow adjustment of the thickness of the deposited layer or sublayer by the rotation speed. Thus, a highly uniform and highly oriented perovskite film can be formed.

[0124] In another aspect of the method for forming a piezoelectric assembly, the first seed layer solution is deposited on at least the piezoelectric layer solution by a printing method such as inkjet printing.

[0125] Precise deposition of the above solutions is possible by allowing a highly spatially defined printing method. Thus, structures or structured films can be produced on a large scale.

[0126] The present invention will be explained in more detail below based on exemplary embodiments and the associated drawings.

[0127] The drawings are only for clarifying the present invention and are therefore shown schematically and not in a true scale manner. Each component can be shown in an enlarged manner or in a distorted manner in terms of size. Therefore, absolute or relative dimensional specifications cannot be inferred from the drawings. Components that are the same or have the same function are provided with the same reference numerals.

[0128] In the figures:

[0129] Figure 1 A first exemplary embodiment of a piezoelectric assembly is shown in a schematic cross-section;

[0130] Figure 2A second exemplary embodiment of the piezoelectric assembly is shown in schematic cross-section;

[0131] Figure 3 A third exemplary embodiment of the piezoelectric assembly is shown in schematic cross-section;

[0132] Figure 4 A scanning electron microscope image showing a cross-section of a portion of a third exemplary embodiment of the piezoelectric assembly;

[0133] Figure 5 A fourth exemplary embodiment of the piezoelectric assembly is shown in schematic cross-section;

[0134] Figure 6 A fourth exemplary embodiment of a piezoelectric assembly in a bent state is shown in schematic cross-section;

[0135] Figure 7 A fifth exemplary embodiment of the piezoelectric assembly is shown in schematic cross-section;

[0136] Figure 8 A sixth exemplary embodiment of the piezoelectric assembly is shown in schematic cross-section;

[0137] Figure 9 X-ray diffraction patterns of piezoelectric assemblies on 20µm and 500µm thick substrates are shown.

[0138] Figure 10 The electric field dependence of the polarization of the piezoelectric assembly with a 20µm thick stainless steel substrate is shown. Figure 10 A) and the real part of the dielectric constant under different DC bias fields ( Figure 10 B); and

[0139] Figure 11 A 500µm thick substrate is shown. Figure 11 A) and a 20µm thick substrate ( Figure 11 The electric field dependence of relative strain (S) and 500µm thick substrate (C) Figure 11 B) and 20µm thick substrate ( Figure 11 The longitudinal piezoelectric coefficient (d) of the piezoelectric film on D) under different DC bias fields 33 ).

[0140] Figure 1 A schematic cross-section of a first exemplary embodiment of the piezoelectric assembly 1 is shown.

[0141] The piezoelectric assembly 1 comprises a nickel-chromium-based austenitic steel substrate 2. The substrate 2 can be, for example, steel such as EN 1.4310, EN 1.4404, EN 1.4541, or EN 1.4845. These steels preferably have oxidation resistance. The substrate 2 includes a main substrate surface 21, which preferably has an arithmetic mean deviation of a surface roughness (Ra) of 200 nm or less.

[0142] The first orientation layer 3 is disposed directly on the surface 21 of the main substrate. The first orientation layer 3 contains lanthanum nickelate (LaNiO3) as the first material of the first orientation layer 3. The perovskite microcrystals of the first material have an orientation degree of 90% or greater, preferably 95% or greater, and most preferably 99% or greater.

[0143] like Figure 1 As shown, the surface of the main substrate can be flat, so all local surface normals are in the same direction.

[0144] The higher the orientation degree of the templated first orientation layer 3, the higher the orientation degree o of the first piezoelectric layer 4 assembled on the first orientation layer 3 will be.

[0145] The total thickness of the first orientation layer 3 can be from 10 nm to 500 nm. For example, the thickness of the orientation layer can be 100-200 nm, such as 150 nm.

[0146] The first piezoelectric layer 4 is composed of a piezoelectric material with a crystalline perovskite structure. In this exemplary embodiment, the piezoelectric material is a lead zirconate titanate-based material, such as lanthanum-doped lead zirconate titanate, for example (La... 0.02 Pb 0.98 (Zr) 0.52 Ti 0.48 )O3.

[0147] The piezoelectric material of the first piezoelectric layer 4 has an orientation degree of 90% or greater. Even more preferably, the orientation degree of the piezoelectric material of the first piezoelectric layer 4 is 95% or greater, or even better, 99% or greater.

[0148] The higher the orientation degree o, the higher the longitudinal piezoelectric coefficient d of the entire layer. 33 The higher the value, the better. With an orientation degree of o within a 99% range, a d value up to 300 pm / V can be achieved. 33 value.

[0149] The thickness of the first piezoelectric layer can be from 100 nm to 5 µm, for example, it can be 600-900 nm.

[0150] The top electrode 5 is disposed on top of the first piezoelectric layer. The top electrode 5 can be composed of any suitable conductive material, such as metal, conductive oxide, or ceramic material. For example, the top electrode can be composed of copper, nickel, gold, silver, platinum, or lanthanum nickelate, or a layered electrode such as Cr / Ni / Ag, Cr / Ni / Au, Ni / Au, Cr / Au, or Ti / Au.

[0151] When in electrical contact with the outside, the substrate 2 and the conductive first orientation layer 3 can be used together as a base.

[0152] A first exemplary embodiment of the piezoelectric assembly 1 can be manufactured by any suitable method. For example, it can be manufactured by the following methods.

[0153] First, an austenitic steel substrate 2 is provided. The surface 21 of the substrate is cleaned by ultrasonic cleaning in acetone, isopropanol, and deionized water. It is then dried in a nitrogen stream. Subsequently, it is treated under ultraviolet light and ozone to remove organic components. Other cleaning methods can be applied. It is important to obtain a near-atomic clean surface that exhibits suitable wettability for the seed layer solution.

[0154] Then, a first seed layer 3 is prepared on the surface 21 of the main substrate, for example by spin coating or screen printing. In the fully processed assembly, the resulting layer can be identified as the first orientation layer 3.

[0155] The first seed layer 3 can be formed through repeated deposition, drying, pyrolysis and annealing processes.

[0156] For example, a 150 nm thick seed layer can be prepared as follows: First, lanthanum acetate and nickel nitrate are dissolved in 2-ethoxyethanol to form a solution with a La-ion and Ni-ion concentration of 0.5 mol / L. The mixture is heated under reflux at 80 °C for 2 hours to obtain a clear solution. After cooling to room temperature, a first seed layer solution with a concentration of 0.2 mol / L is formed by adding solvent.

[0157] To prepare a first seed layer 3 with a thickness of approximately 150 nm, a spin-coating deposition, drying, pyrolysis, and annealing process can be performed six times. One preparation cycle includes: depositing the first seed layer solution onto the surface 21 of the main substrate by spin-coating at a speed of 3000 rpm for 30 s. Subsequently, the solvent is removed by drying at approximately 100°C to 200°C. A pyrolysis step (first pyrolysis process) is then performed at a first pyrolysis temperature of 300°C to 450°C to remove other organic components. The first holding time at the first pyrolysis temperature can be from 0.1 min to 10 min, typically from 0.5 min to 5 min. This forms an amorphous primary seed layer. Subsequently, the film is annealed at a temperature of 600-750°C to crystallize it. The first heating rate is typically 10 K / s or higher, for example, 30 K / s, preferably, as it facilitates the growth of the first seed layer with a crystal orientation 100. Annealing can be performed in a nitrogen-oxygen mixture with a nitrogen-oxygen ratio of 4:1 to ensure the stoichiometric oxygen content in the seed layer.

[0158] The thickness of the first seed layer 3 can be changed by adjusting the number of deposition cycles.

[0159] A highly oriented first piezoelectric layer 4 can be fabricated on the highly oriented seed layer 3.

[0160] The preparation of the first piezoelectric layer 4 is in principle very similar to the preparation of the first seed layer 3. It can also be based on a process of repeated deposition, drying, pyrolysis, and annealing of the piezoelectric layer solution.

[0161] The piezoelectric layer solution can be prepared by first preparing a solution containing ions of lead zirconate titanate piezoelectric material. For example, for a composition of (La... 0.02 Pb 0.98 ) (Zr 0.52 Ti 0.48 A piezoelectric material based on O3 was prepared by dissolving zirconium propoxide (0.52 mol / L), titanium isopropoxide (0.48 mol / L), anhydrous lead acetate (1.127 mol / L), and anhydrous lanthanum acetate (0.02 mol / L) in 2-methoxyethanol. In this solution, lead was present in excess at 15 mol% relative to the required stoichiometry for the piezoelectric material to compensate for lead loss during the heating steps in the preparation process. A clear solution was obtained by heating under reflux to approximately 120 °C for 2 hours and then distilling. The piezoelectric material was prepared by adding a solvent to obtain a solution containing (La) 0.02 Pb 0.98 ) (Zr 0.52 Ti 0.48 A piezoelectric layer solution with an O3 concentration of 0.5 mol / L and a lead excess of 15 mol%.

[0162] Piezoelectric layers can be produced through a repetitive deposition, drying, pyrolysis, and annealing process. For example, for a layer thickness on the order of 780 nm, the following procedure can be applied: First, a piezoelectric layer solution is deposited by spin coating at 3000 rpm for 30 seconds. Then, the deposited solution is dried at 100-200 °C. Next, a pyrolysis step is performed at 300-450 °C to remove organic components. This produces an amorphous primary piezoelectric layer. This process can be repeated up to three times. This means that three amorphous sublayers can be assembled one after another. Subsequently, an annealing process is performed at 500-700 °C in a nitrogen-oxygen mixture with a nitrogen-oxygen ratio of 4:1 for less than 15 minutes. For example, the annealing time can be 1-5 minutes. This process can be repeated four times, meaning that the entire 780 nm first piezoelectric layer is formed from 12 primary sublayers.

[0163] The thickness of the first piezoelectric layer 4 can be changed by adjusting the number of deposition cycles.

[0164] The external electrode 5 can be deposited using any suitable technique, such as sputtering or burn-in procedures.

[0165] Figure 2 A schematic cross-section of a second exemplary embodiment of the piezoelectric assembly 1 is shown.

[0166] Apart from the first orientation layer 3 having a layered structure, the second exemplary embodiment may be the same as the first exemplary embodiment.

[0167] The first orientation layer 3 consists of a dense orientation sublayer 31 and a porous orientation sublayer 32. Both are composed of the same first material as the first orientation layer 3 in the first exemplary embodiment.

[0168] However, the dense oriented sublayer 31 has a density that is at least twice that of the porous oriented sublayer 32, or in other words, a porosity that is at most half that of the porous oriented sublayer 32.

[0169] The porous orientation sublayer 32 is composed of a porous material with an average pore size of less than 100 nm, preferably 1 nm to 20 nm.

[0170] The advantage of this assembly is that the dense oriented sublayer 31, which is directly assembled on the austenitic steel substrate 2, can be an effective buffer layer that prevents mutual diffusion between the first piezoelectric layer 4 and the substrate 2.

[0171] The porous orientation sublayer 32 can provide stress relaxation between the substrate 2 and the first piezoelectric layer 4, thereby reducing the substrate clamping effect.

[0172] In such assemblies, the relative strain S of the piezoelectric material can exceed 0.7%. This is a value comparable to that of piezoelectric films achieved on expensive silicon wafer substrates.

[0173] The preparation procedure of the second exemplary embodiment can be the same as that of the first exemplary embodiment, but the first seed layer 3 is adjusted.

[0174] Typically, the dense seed layer 31 can be prepared by a deposition, drying, pyrolysis, and annealing process described for preparing the entire first seed layer 3 of the first exemplary embodiment. This process can be repeated, for example, three times.

[0175] For the porous seed layer 32, two main preparation techniques can be applied. In the first option, a second seed layer solution is first prepared, identical to the first seed layer solution, except for a lower concentration of Ni- and La- ions of 0.1-0.15 mol / L. Deposition, drying, and annealing can be the same as those used for the preparation of the dense seed layer 31. For the porous seed layer 32, a second pyrolysis procedure is applied. The second pyrolysis procedure is characterized by a second pyrolysis temperature T2 and a second holding time t2. To ensure that the porosity of the porous seed layer 32 is higher than that of the dense seed layer 31, either the second pyrolysis temperature T2 must be lower than the first pyrolysis temperature, or the second holding time t2 must be shorter than the first holding time. For example, where T1 = T2, t2 can be less than 2 min, e.g., 0.5 min, and t1 can be greater than 2 min, e.g., 5 min.

[0176] The procedure can be repeated to achieve the desired thickness of the porous crystal seed layer 32.

[0177] A second option for producing the porous seed layer 32 is based on the use of a polymer. A polymer can be added to the aforementioned second seed layer solution. The polymer can be, for example, polyvinylpyrrolidone, which can be added at a rate of 1 g / 5 ml. The prepared solution can be stirred for 24 hours and filtered through a 0.2 µm filter. In principle, other polymers, such as polymethyl methacrylate or polyethylene glycol, can also be used, depending on, for example, their solubility in the solvent and the conditions of the pyrolysis step.

[0178] Similar to the first seed layer solution, a porous seed layer 32 can be formed using a second seed layer solution containing a polymer. However, the temperature of the pyrolysis step must be selected to prevent complete decomposition and dissipation of the polymer. Polymer residues remain in the formed amorphous porous seed layer. These residues prevent the formation of a closed and dense seed layer. Only in the third annealing process does the polymer completely dissociate and dissipate. At these temperatures, the perovskite material can crystallize effectively. However, almost no sintering occurs under these conditions.

[0179] In the completed piezoelectric assembly, the dense crystal seed layer 31 can be identified as the dense oriented sublayer 31, and the porous crystal seed layer 32 can be identified as the porous oriented sublayer 32.

[0180] Figure 3 A third exemplary embodiment of the piezoelectric assembly 1 is shown. It is identical to the first exemplary embodiment of the piezoelectric assembly, except for the first orientation layer 3.

[0181] The first orientation layer 3 includes a dense orientation sublayer 31 directly attached to the surface 21 of the main substrate. It includes a porous orientation sublayer 32 directly above the dense orientation sublayer 31. Furthermore, it includes another dense orientation sublayer 33 disposed directly on the porous orientation sublayer 32. The fabrication process of the porous and dense orientation sublayers can be similar to that of the first orientation layer 31. Figure 2 It is performed as described in the second exemplary embodiment shown.

[0182] Preferably, the dense orientation sublayers 31 and 33 are thinner than the porous orientation sublayer 32. This allows for chemical buffering through the lower dense orientation sublayer 31. Furthermore, the upper dense orientation sublayer 33 forms a smooth, continuous surface on which a high-quality piezoelectric film can be formed. Additionally, the thicker porous orientation sublayer 32 allows for effective stress release between the substrate 2 and the first piezoelectric layer 4. For example, the thickness ratio between the lower dense orientation sublayer 31, the porous orientation sublayer 32, and the upper dense orientation sublayer 33 can be 1:4:1. For example, the total thickness can be 150 nm.

[0183] Figure 4 As shown Figure 3 The cross-sectional scanning electron microscope (SEM) image of the piezoelectric assembly 1 shown shows the external electrode 5, which is not present in the sample in the SEM image.

[0184] exist Figure 4 In the SEM images, the layers of the piezoelectric assembly 1 can be clearly identified and marked accordingly. Interestingly, a chromium-rich layer 22 has formed near the surface 21 of the main substrate, and it is visible as a darkening layer in the piezoelectric assembly 1. It is believed that the chromium enrichment occurs during a pyrolysis or annealing process. Energy-dispersive X-ray spectroscopy (EDX) confirmed the absence of Cr or other elements that form the substrate in the first piezoelectric layer. Therefore, EDX can demonstrate that the provided first orientation layer can exhibit an effective buffering function.

[0185] Figure 5 A schematic cross-section of a fourth exemplary embodiment of the piezoelectric assembly 1 is shown.

[0186] The layer assembled on the surface 21 of the main substrate 2 can be with Figure 1The first exemplary embodiment shown is identical. Furthermore, in principle, the orientation layer 3 can also be implemented similarly to the second or third exemplary embodiment.

[0187] In this fourth exemplary embodiment, the substrate 2 includes a second substrate surface 21' opposite to the main substrate surface 21. An alignment layer 3', which may be the same as the first alignment layer 3, is assembled on the second substrate surface 21'. Furthermore, a piezoelectric layer 4', which may be the same as the first piezoelectric layer 4, is assembled on the alignment layer 3'. In addition, a second external electrode 5' is assembled on the piezoelectric layer 4'.

[0188] This means that symmetrical stacking is achieved on the surface 21 of the main substrate and the surface 21' of the second substrate.

[0189] In this arrangement, the substrate 2 and the alignment layers 3 and 3' can form internal electrodes.

[0190] The preparation process can be similar to that for Figure 1 The preparation process described in the first exemplary embodiment shown.

[0191] Figure 6 A fourth exemplary embodiment of a piezoelectric assembly in a bent state is shown. It can be implemented on a bent substrate, or it can be arranged in an application where it becomes bent. This means that for... Figure 5 The symmetry described in the embodiment shown is maintained only along the local surface normal of the main substrate surface, which means that for each point along the local surface normal direction, each layer is mirror equivalent on both sides of the substrate 2.

[0192] Figure 7 A fifth exemplary embodiment of the piezoelectric assembly is shown in schematic cross-section.

[0193] It is based on, for example Figure 1 The first exemplary embodiment of the piezoelectric assembly shown is illustrated. However, in the first exemplary embodiment, an additional layer is arranged on the electrode 5, which is the outer electrode 5.

[0194] The second orientation layer 6 is disposed directly on the electrode 5, thus making the electrode 5 an internal electrode. In principle, the second orientation layer 6 can be identical to the first orientation layer 3. A second piezoelectric layer 7 is disposed on the second orientation layer 6, which can be identical to the first piezoelectric layer 4. This specifically means that the composition and orientation degree α of the second orientation layer 6 and the second piezoelectric layer 7 can be identical to those of the first orientation layer 3 and the first piezoelectric layer 4, respectively. An external electrode 8 is disposed on the second piezoelectric layer 7.

[0195] The preparation process can be similar to that for Figure 1 The preparation process described in the first exemplary embodiment shown.

[0196] In such an assembly, the substrate 2 having the first alignment layer 3 can be used as the base electrode. The electrode 5, together with the second alignment layer 6, can be used as an internal electrode.

[0197] Figure 8 A sixth exemplary embodiment of the piezoelectric assembly 1 is shown. It is related to... Figure 7 The fifth exemplary embodiment of the piezoelectric assembly shown is the same as that in the sixth exemplary embodiment, except that the internal electrode 5 is absent. Instead, the second orientation layer 6 is disposed directly on the first piezoelectric layer 4.

[0198] In this arrangement, the second orientation layer 6 can be used as an internal electrode when in electrical contact.

[0199] Figure 9 Showing something similar Figure 4 The image shows an X-ray diffraction pattern of the piezoelectric layer assembly. Both samples contain a nickel-chromium-based austenitic steel substrate, one with a thickness of 20 µm and the other with a thickness of 500 µm.

[0200] The intensities of the (100) and (200) diffraction peaks of the two samples were compared with the intensities of the (110) and (111) peaks, and based on the Lotgering factor (LF) found to be higher than 99% for both samples... 100 The evaluation was conducted. This is equivalent to an orientation degree of 99% or higher for the crystalline perovskite structure of the first piezoelectric layer.

[0201] This proves that highly oriented piezoelectric films can be prepared through the above procedure.

[0202] Figure 10 Provided for Figure 9 The analysis of the electrical properties of the assembly with a 20µm thick substrate is discussed in the paper. For measurement, a sputtered gold electrode 5 with a diameter of 500µm was formed on the first piezoelectric layer 3.

[0203] Measurements were performed using an Aixacct TF2000FE with a 100Hz sinusoidal test signal.

[0204] Figure 10 A shows the electric field dependence of polarization under different DC bias fields.

[0205] Typical ferroelectric square hysteresis loops were observed in polarization electric field measurements, with saturation polarization exceeding 40 µC / cm. 2 The coercive field was observed to be 50 kV / cm.

[0206] Figure 10 B shows the dependence of the real part of the dielectric constant on the DC bias field.

[0207] The real part of the complex permittivity is close to 600 in a 0 DC field and close to 700 in a coercive field.

[0208] For piezoelectric thin films prepared on metal foils, these values ​​are much larger than previously reported, for example, compared to the film of EP1282901 B1, where only about 150 dielectric constant was measured. This indicates that excellent piezoelectric assemblies can be formed using the methods described above.

[0209] Figure 11 Showing the Figure 9 The results of two-beam laser interferometry measurements recorded at a frequency of 1 kHz for the two samples mentioned in the context. Both the 20 µm and 500 µm substrate samples have a 500 µm diameter gold electrode disposed on the first piezoelectric layer.

[0210] Figure 11 A shows the electric field dependence of the relative strain (S) of a piezoelectric assembly with a 500µm thick substrate. Figure 11 B shows the longitudinal piezoelectric coefficient d of the piezoelectric assembly on a 500µm thick substrate. 33 It depends on the electric field.

[0211] The equivalent curves of the sample with a 20µm thick substrate are respectively at Figure 11 As shown in C and 11D.

[0212] Relative strain (S) can be understood as relative displacement, perpendicular to the membrane normal and induced by the electric field in the piezoelectric assembly. S is measured using a sinusoidal test signal at 100 Hz. The longitudinal piezoelectric coefficient d... 33 It is extracted from field-induced displacement measurement using a 0.5V AC signal at 1kHz.

[0213] For assemblies with a substrate thickness of 500µm, the S value exceeds 0.15%. This is equivalent to a longitudinal piezoelectric coefficient d exceeding 70pm / V. 33 The peak value.

[0214] For assemblies on a 20µm thick substrate, even higher values ​​can be obtained, exceeding 0.7% relative strain S. This is equivalent to approximately 300 pm / V d. 33 value.

[0215] Please note that, for Figure 11 The fluctuations in the hysteresis curve of D for measurements at low or high electric fields may be caused by minute deviations in the substrate thickness, which in turn affect the measurement during the piezoelectric bending of the substrate.

[0216] To the best of the author's knowledge, these values ​​are the highest reported for piezoelectric thin films on steel substrates. Non-Patent Literature 2 is compared, for example, in this paper. The achieved values ​​are even comparable to those of piezoelectric thin film elements fabricated on standard silicon wafer substrates containing noble metal electrode materials. Non-Patent Literature 1 is compared, for example, in this paper.

[0217] Reference list:

[0218] 1. Piezoelectric assembly

[0219] 2. Substrate

[0220] 21 Main substrate surface

[0221] 21' Second substrate surface

[0222] 3 First Orientation Layer

[0223] 3' Orientation layer

[0224] 31 Dense Oriented Sublayer

[0225] 32 Porous Oriented Sublayer

[0226] 33 Dense Oriented Sublayer

[0227] 4 First piezoelectric layer

[0228] 4' piezoelectric layer

[0229] 5 electrodes

[0230] 5' electrode

[0231] 6 Second Orientation Layer

[0232] 7 Second piezoelectric layer

[0233] 8 electrodes.

Claims

1. A piezoelectric assembly (1), comprising: - Base metal substrate (2), which has a main substrate surface (21), - A first orientation layer (3) is disposed on the surface (21) of the main substrate, wherein - The first orientation layer (3) comprises a first material with a crystalline perovskite structure, wherein the first material constitutes at least 90 wt% of the first orientation layer. - A first piezoelectric layer (4) is disposed on the first alignment layer (3), wherein - The first piezoelectric layer (4) comprises a lead-containing piezoelectric material with a crystalline perovskite structure, and the piezoelectric material has a larger longitudinal piezoelectric coefficient (d) along the direction (100) than the first material of the first orientation layer (3). 33 ), - The orientation degree o of the piezoelectric material in the first piezoelectric layer (4) is 90% or greater, wherein the orientation degree o is the average alignment degree between the orientation (100) of the cell of the crystalline piezoelectric material and the local surface normal N of the surface (21) of the main substrate. - Wherein the first orientation layer includes a porous orientation sublayer, the porous orientation sublayer having a porous structure with a relative porosity of up to 70%. - Wherein the first orientation layer includes a dense orientation sublayer, and the porous orientation sublayer has a pore concentration at least twice that of the dense orientation sublayer. The dense orientation sublayer is disposed directly on the surface of the main substrate, and the porous orientation sublayer is disposed on the dense orientation sublayer.

2. The piezoelectric assembly (1) according to claim 1, wherein - The substrate (2) has a second substrate surface (21') opposite to the surface of the main substrate (21), and - A layered structure including a piezoelectric layer (4') on an alignment layer (3') is arranged on the surface (21') of the second substrate, similar to the first piezoelectric layer (4) on the first alignment layer (3) on the surface (21) of the main substrate.

3. The piezoelectric assembly (1) according to claim 1, wherein - A second orientation layer (6) made of the first material is disposed above the first piezoelectric layer (4). - A second piezoelectric layer (7) is disposed on the second alignment layer (6), wherein - The second piezoelectric layer (7) contains the same piezoelectric material as the first piezoelectric layer (4) having the same orientation degree o of 90% or greater.

4. The piezoelectric assembly according to claim 3, wherein a further dense orientation sublayer (33) is arranged on the porous orientation sublayer (32).

5. The piezoelectric assembly (1) according to claim 1, wherein the average pore size of the porous orientation sublayer (32) is 100 nm or less.

6. The piezoelectric assembly (1) according to claim 1, wherein the first material of the first orientation layer (3) is selected from LaNiO3, SrRuO3 and PbTiO3.

7. The piezoelectric assembly (1) according to claim 1, wherein the first material of the first orientation layer (3) has an orientation degree of at least 90% or greater than that of the crystalline perovskite structure of the first piezoelectric layer (4).

8. The piezoelectric assembly according to claim 1, wherein the first orientation layer (3) has a thickness of 10 nm to 500 nm.

9. The piezoelectric assembly (1) according to claim 1, wherein the substrate (2) is titanium (Ti), aluminum (Al), nickel (Ni), copper (Cu) or steel.

10. The piezoelectric assembly (1) according to claim 1, wherein the piezoelectric material is composed of the formula [Pb] 1-y S 1 y ][(Zr x Ti 1-x ) 1-z S 2 z O3 indicates that, among which - S 1 It is the first substituent. - S 2 It is the second substituent. - 0.40≤x≤0.95， - y < 0.3, and - z<0.15。 11. The piezoelectric assembly (1) according to claim 1, wherein the first piezoelectric layer (4) has a thickness of 0.1 μm to 5 μm.

12. An apparatus comprising a piezoelectric assembly (1) according to claim 1, wherein the piezoelectric assembly (1) is attached to a surface of the apparatus and configured to generate a tactile signal at the surface.

13. An apparatus comprising a piezoelectric assembly (1) according to claim 1 and an energy storage element, The piezoelectric assembly (1) is configured to collect electrical energy generated in the piezoelectric assembly (1) during mechanical deformation, and The energy storage element is configured to store electrical energy collected by the piezoelectric assembly (1).

14. A micromirror comprising the piezoelectric assembly (1) according to claim 1, wherein - The micromirror includes a mirror surface on a piezoelectric assembly, and - The piezoelectric assembly (1) is configured to bend the micromirror when a voltage is applied to the piezoelectric assembly (1).

15. A method for forming a piezoelectric assembly (1), comprising: - Provide a base metal substrate (2) having a main substrate surface (21), - Forming a first seed layer (3) on the surface (21) of the main substrate, comprising a first material containing a crystalline perovskite structure represented by the general formula ABO3, including the following steps: - A first seed layer solution containing A ions and B ions is deposited on the surface (21) of the main substrate. - The first seed layer (3) is prepared as a layered structure, which includes the following steps: - Deposit a first seed layer solution containing A and B ions. - Forming a dense seed layer (31), which includes a first pyrolysis process characterized by a first pyrolysis temperature T1 and a first holding time t1 at the first pyrolysis temperature T1. - Deposit a second seed layer solution containing A and B ions. - Forming a porous seed layer (32), which includes a second pyrolysis process characterized by a second pyrolysis temperature T2 and a second holding time t2 at the second pyrolysis temperature T2. - The perovskite structure is crystallized through a first annealing process. - Forming a first piezoelectric layer (4), the first piezoelectric layer (4) comprising a lead-containing piezoelectric material with a crystalline perovskite structure, comprising the following steps: - Deposit a piezoelectric layer solution containing lead ions and other ions of the piezoelectric material. - The lead-containing perovskite structure is crystallized through a second annealing process. The dense crystal seed layer (31) is directly prepared on the surface (21) of the main substrate, and the porous crystal seed layer (32) is prepared on top of the dense crystal seed layer (31).

16. The method of forming a piezoelectric assembly (1) according to claim 15, wherein T2 < T1, and / or t2 < t1.

17. The method for forming a piezoelectric assembly (1) according to claim 15, wherein - The second seed layer solution contains a polymer, and - Perform the second pyrolysis procedure to cause the polymer to decompose and dissipate incompletely.

18. The method of forming a piezoelectric assembly (1) according to claim 15, wherein at least the first seed layer solution or the piezoelectric layer solution is deposited by spin coating.

19. The method of forming a piezoelectric assembly (1) according to claim 15, wherein at least the first seed layer solution or the piezoelectric layer solution is deposited by a printing method.

20. A piezoelectric assembly (1), comprising: - Base metal substrate (2), which has a main substrate surface (21), - A first orientation layer (3) is disposed on the surface (21) of the main substrate, wherein - The first orientation layer (3) comprises a first material with a crystalline perovskite structure, the first material constituting at least 90 wt% of the first orientation layer. - A first piezoelectric layer (4) is disposed on the first alignment layer (3), wherein - The first piezoelectric layer (4) comprises a lead-containing piezoelectric material with a crystalline perovskite structure, and the piezoelectric material has a larger longitudinal piezoelectric coefficient (d) along the direction (100) than the first material of the first orientation layer (3). 33 ), - The orientation degree o of the piezoelectric material in the first piezoelectric layer (4) is 90% or greater, wherein the orientation degree o is the average alignment degree between the orientation (100) of the unit cell of the crystalline piezoelectric material and the local surface normal N of the surface (21) of the main substrate. - The substrate (2) has a second substrate surface (21') opposite to the surface of the main substrate (21), and - A layered structure including a piezoelectric layer (4') on an alignment layer (3') is arranged on the surface (21') of the second substrate, similar to the first piezoelectric layer (4) on the first alignment layer (3) on the surface (21) of the main substrate. - Wherein the first orientation layer includes a porous orientation sublayer, the porous orientation sublayer having a porous structure with a relative porosity of up to 70%. - Wherein the first orientation layer comprises at least one dense orientation sublayer, and the porous orientation sublayer has a pore concentration at least twice that of the dense orientation sublayer. - The dense orientation sublayer is disposed directly on the surface of the main substrate, and the porous orientation sublayer is disposed on the dense orientation sublayer.

21. A piezoelectric assembly (1), comprising: - Base metal substrate (2), which has a main substrate surface (21), - A first orientation layer (3) is disposed on the surface (21) of the main substrate, wherein - The first orientation layer (3) comprises a first material with a crystalline perovskite structure, the first material constituting at least 90 wt% of the first orientation layer. - A first piezoelectric layer (4) is disposed on the first alignment layer (3), wherein - The first piezoelectric layer (4) comprises a lead-containing piezoelectric material with a crystalline perovskite structure, and the piezoelectric material has a larger longitudinal piezoelectric coefficient (d) along the direction (100) than the first material of the first orientation layer (3). 33 ), - The orientation degree o of the piezoelectric material in the first piezoelectric layer (4) is 90% or greater, wherein the orientation degree o is the average alignment degree between the orientation (100) of the unit cell of the crystalline piezoelectric material and the local surface normal N of the surface (21) of the main substrate. - A second orientation layer (6) composed of the first material is disposed above the first piezoelectric layer (4). - A second piezoelectric layer (7) is disposed on the second orientation layer (6), wherein the second piezoelectric layer (7) comprises the same piezoelectric material as the first piezoelectric layer (4) having the same degree of orientation o of 90% or greater. - Wherein the first orientation layer includes a porous orientation sublayer, the porous orientation sublayer having a porous structure with a relative porosity of up to 70%. - Wherein the first orientation layer comprises at least one dense orientation sublayer, and the porous orientation sublayer has a pore concentration at least twice that of the dense orientation sublayer. - The dense orientation sublayer is disposed directly on the surface of the main substrate, and the porous orientation sublayer is disposed on the dense orientation sublayer.

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