Piezoelectric material having a perovskite structure for high operating temperature and its manufacturing process

Abstract

The present invention relates to a compound having a perovskite structure, which has a basic composition, the basic composition Ag x Bi y M z Fe v N w O3, where x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1, M is selected from Pb and / or Ba, N is selected from Ti and / or Zr, and it can be used as a basic raw material for the production of perovskite materials having piezoelectric properties at high temperatures and functional ceramics. Furthermore, a process for producing a material having piezoelectric functionality is described, which guarantees consistent high product quality, provides advantages regarding safety, and enables production without using organic solvents. Furthermore, a piezoelectric device comprising the aforementioned perovskite material or a compound having a perovskite structure is described.

Description

Technical Field

[0001] Description Technical Field The present invention relates to a composition having a perovskite structure that can be used as a starting material for manufacturing perovskite functional ceramics having piezoelectric properties at high temperatures.

[0002] In addition, a method for manufacturing a material containing a specific composition and a piezoelectric device containing the material are described.

Background Art

[0003] Background Art Piezoelectric materials are characterized in that their electric polarization changes as a result of a mechanical action (piezoelectric effect), or the application of a voltage causes a change in the dimensions of the material or its mechanical operation (inverse piezoelectric effect). Based on these functions, piezoelectric elements are widely used in many technical fields as both sensors and actuators, for example, in medical technology, sonar applications, ultrasonic technology, household appliances, mechanical engineering, the automotive industry, and aerospace.

[0004] The state of the art describes a number of materials suitable as base materials for piezoelectrically active components. For example, German Patent No. 102019135245 B9 discloses a piezoelectric composition containing silver and oxides, the oxides having a perovskite structure and being at least partially represented by the chemical formula x[Bi m FeO3]-y[Ba n TiO3].

[0005] The most common piezoelectric materials today are the ferroelectric crystal lead zirconate titanate Pb(Zr x Ti (1-x))It is manufactured based on O3(PZT), which usually has a perovskite structure like similar barium titanates. Perovskite refers to the general structural type of the closest-packed ionic structure ABX3, where A and B are cations and X is an anion. Distortion of the perovskite structure can cause polarization within the crystal lattice and thus dipole formation, which is the cause of the piezoelectric properties of many perovskites. For example, in lead zirconate titanate (PZT) below the Curie temperature (T c ), titanium ions within the ionic lattice move from their central positions, resulting in a dipole lattice with piezoelectric properties.

[0006] However, the temperature range for using PZT is very limited. Permanently, and with a sufficient piezoelectric coefficient exceeding 50 pC / N (accompanied by a change in length along the electric field and the poling axis (longitudinal effect)) d 33 While maintaining, the maximum temperature at which PZT can be used is usually about 250 °C.

[0007] To solve this problem, materials with improved piezoelectric functionality at high temperatures are described in International Publication No. WO 2019 / 243778 A1, US Patent Application Publication No. US 2013 / 0207020 A1, and US Patent Application Publication No. US 2018 / 0315916 A1, and perovskite materials (Bi a K 1-a )TiO 3-y BiFeO3 - PbTiO3 (or an alternative chemical formula notation where x + y + z = 1.0 and v + w = 1.0, K x Bi y Pb z Fe v Ti w O3) act as the material base raw materials.

[0008] In International Publication No. WO 2019 / 243778 A1, US Patent Application Publication No. US 2013 / 0207020 A1, and US Patent Application Publication No. US 2018 / 0315916 A1, (Bi a K 1-a )TiO 3-yAs part of the production of BiFeO3-PbTiO3, in addition to Bi2O3, Fe2O3, and TiO2, PbO is weighed and mixed as the lead component, and K2CO3 is mixed as the potassium component.

[0009] Potassium carbonate (K2CO3) is highly hygroscopic and has a water solubility of L = 1120 g / l at 25 °C, but alternative potassium compounds are also usually hygroscopic and water-soluble (e.g., at 25 °C each, KOH: L = 1130 g / l, KNO3: L = 316 g / l, K2C2O4: L = 360 g / l, K2CO3: L = 1120 g / l, KCl: L = 347 g / l). These properties pose significant challenges to the manufacturing process of piezoelectric ceramic materials from the following aspects.

[0010] The significant hygroscopicity of potassium compounds leads to a certain absorption of humidity, making it difficult to accurately and quantitatively weigh the reactants, which can particularly adversely affect the product quality and the reproducibility of the manufacturing process unless controlled ambient conditions are ensured at a significant cost and effort.

[0011] The high water solubility of potassium compounds also requires mixing with an anhydrous medium of an organic liquid. Each solvent such as isopropyl alcohol used in US Patent Application Publication No. 2013 / 0207020 A1 and US Patent Application Publication No. 2018 / 0315916 A1 is flammable. Therefore, particularly with regard to the upscaling of the manufacturing process, complex safety precautions are required. Nevertheless, it is desirable to minimize the use of organic solvents in the manufacturing process, especially for environmental reasons.

[0012] European Patent Application Publication No. 3331840 A1 describes a process in which starting materials are homogenized in an aqueous suspension and then subjected to spray freeze granulation in order to prevent water-soluble components such as alkalis from dissolving during subsequent processing and separating during drying. However, in addition to the need for additional process steps, this process cannot minimize the inaccuracy of weighing the starting materials.

[0013] WO 2019 / 243778 A1 describes a dry mixing without a liquid medium. However, this process is associated with significant drawbacks as the hygroscopic properties of the potassium compound during supply and actual dry mixing can lead to aggregation, which in turn can lead to an unfavorable non-uniform mixing distribution that may reduce the quality of the resulting material. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0014] In view of the above, the object of the present invention is, therefore, to provide compounds and materials that are characterized by excellent piezoelectric functionality at high temperatures and that can be provided in high quality and in large quantities using a simple, cost-effective, and environmentally friendly process. MEANS FOR SOLVING THE PROBLEM

[0015] SUMMARY OF THE INVENTION Accordingly, as a solution to the above problems, the present invention provides a compound having a perovskite structure, having a basic composition Ag x Bi y M z Fe v N w O3, where x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1, M is selected from Pb and / or Ba, and N is selected from Ti and / or Zr.

[0016] Furthermore, there is provided a material having piezoelectric functionality, characterized by including a perovskite material containing the aforementioned compound.

[0017] Furthermore, the present invention provides a method for manufacturing the aforementioned material having piezoelectric functionality. Furthermore, a piezoelectric device is described that preferably comprises a piezoelectric ceramic body having at least two electrodes, the piezoelectric device including the aforementioned compound having a perovskite structure or the aforementioned material having piezoelectric functionality.

[0018] Advantageous embodiments of the present invention can be understood from the dependent claims and the following description. The present invention will be described in more detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2A

Figure 2B

Modes for Carrying Out the Invention

[0020] Detailed Description of the Invention The present invention and its advantages will be described in more detail below with reference to the preferred embodiments.

[0021] x Bi y M z Fe v N w In one embodiment, the present invention relates to a compound having a perovskite structure, wherein the compound has a basic composition Ag

[0022] In a preferred embodiment, M includes both Pb and Ba, so the compound has a basic composition Ag x Bi y (Pb,Ba) z Fe v N w O3, and z is the total mass fraction of both metals in the basic composition.

[0023] In a further preferred embodiment, M represents Pb, so the compound has a basic composition Agx Bi y Pb z Fe v N w has O3.

[0024] Preferably, the sum of x, y, and z is 0.95 to 1.05, and the sum of v and w = 0.95 to 1.05. Particularly preferably, x + y + z = 1 and v + w = 1. Generally, x, y, z, v, and w are independent of each other and satisfy 0 < x < 1, 0 < y < 1, 0 < z < 1, 0 < v < 1, and 0 < w < 1.

[0025] Silver compounds characterized by relatively low water solubility and non-hygroscopic properties have been found to be easy to handle and enable the production of materials with excellent piezoelectric properties at high temperatures.

[0026] In a preferred embodiment, x, y, z, v, and w are 0.005 ≦ x ≦ 0.30 0.40 ≦ y ≦ 0.90 0.01 ≦ z ≦ 0.70 0.40 ≦ v ≦ 0.80 0.20 ≦ w ≦ 0.60 satisfy.

[0027] In a more preferred embodiment, x, y, z, v, and w are 0.01 ≦ x ≦ 0.20 0.50 ≦ y ≦ 0.80 0.05 ≦ z ≦ 0.50 0.50 ≦ v ≦ 0.70 0.30 ≦ w ≦ 0.50 satisfy.

[0028] In a particularly preferred embodiment regarding the piezoelectric properties in the high temperature range (e.g., determined by T c and d 33 ), x, y, z, v, and w are 0.02 ≦ x ≦ 0.14 0.56 ≦ y ≦ 0.76 0.10 ≦ z ≦ 0.42 0.54 ≤ v ≤ 0.62 0.38 ≤ w ≤ 0.46 satisfy the following conditions

[0029] Perovskite is characterized by the general structural type of the closest-packed ionic structure ABX3, where A and B represent cations and X represents an anion. In this regard, in the compounds according to the present invention, it is preferred that Ag and Bi (or Ag + and Bi 3+ ) occupy the position A in the perovskite basic structure ABO3 as a basis. Further, alternatively, in the compounds according to the present invention, it is preferred that Fe and Ti or Zr (or Fe 3+ and Ti 4+ or Zr 4+ ) occupy the position B in the perovskite basic structure ABO3 as a basis.

[0030] Generally, the compounds according to the present invention exhibit an orthorhombic / rhombohedral structure. The Goldschmidt tolerance factor t defines the lower limit of the tolerance error according to the ionic radii for forming the perovskite structure (see V.M. Goldschmidt: Die Gesetze der Krystallochemie. In: Die Naturwissenschaften, Vol. 14, No. 21, 1926, pages 477 - 485). This also makes it possible to estimate the degree of strain and to describe the ratio of bond lengths. The compounds according to the present invention preferably have a perovskite structure tolerance factor t according to Goldschmidt in the range of 0.820 - 0.880, more preferably in the range of 0.840 - 0.860. To calculate the Goldschmidt tolerance factor t according to the present invention, the effective ionic radii according to R.D. Shannon, "Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides", Acta Crystallography, A32, 1976, 751 - 767 are used.

[0031] In a further embodiment, the present invention provides a material having piezoelectric functionality, characterized by comprising a perovskite material containing the above-described compound having a perovskite structure.

[0032] Preferably, the total amount of the non-perovskite phase present in the material is less than 10% by weight, more preferably less than 8% by weight, more preferably less than 5% by weight, even more preferably less than 2% by weight, even more preferably less than 1% by weight, and most preferably less than 0.1% by weight. The amount of the non-perovskite phase present in the ceramic can be trace.

[0033] Particularly preferably, the material consists of a pure perovskite material with respect to X-rays without non-perovskite heterophases detectable by X-rays.

[0034] The perovskite material can also include one or more perovskite phases in addition to the basic composition Ag x Bi y M z Fe v N w O3 where x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1. The additional perovskite phase may have a rhombohedral crystal structure or a tetragonal crystal structure. The perovskite material preferably does not include a perovskite phase having the chemical formula (Bi a K 1-a )TiO3 with 0.4 ≦ a ≦ 0.6. In a more preferred embodiment, the perovskite material does not contain potassium ions.

[0035] In the perovskite material contained in the material, one or more of Ag, Bi, M, Fe, and N can be substituted by a dopant to modify, for example, the Curie temperature and / or the piezoelectric activity.

[0036] The dopant may be added in a suitable amount, for example, in an amount of up to 2 wt%, preferably up to 1 wt%, in embodiments up to 50 atomic%, or up to 20 atomic%. It is more preferable that the dopant is added in an amount of at least 0.001 wt%, more preferably at least 0.005 wt%. The numbers of wt% refer to the total weight of the perovskite material.

[0037] Preferred dopants are metal dopants. For example, the metal dopant functions as a substituent at the A position within the basic perovskite basic structure ABO3 and can replace, for example, Ag and / or Bi. Preferably, the metal dopant for the A position is selected from the group consisting of Li, Na, Ca, Sr, Ba, and rare earth metals. Doping with Li, Na, Ca, Sr, or Ba at the A position can reduce dielectric loss, modify the Curie point (e.g., increase it), and / or have a beneficial effect on the phase composition, while substitution with rare earth metals (such as La or Nd) may improve the piezoelectric activity.

[0038] The metal dopant can be a metal dopant for the B position within the basic perovskite basic structure ABO3 and can replace, for example, Fe and / or Ti.

[0039] Preferred dopants for the B position can be selected, for example, from the group consisting of Ti, Zr, W, Nb, V, Ta, Mo, and Mn. Preferred metal dopants for the B position can have a valence higher than that of the substituted metal, thereby increasing the resistivity of the material and decreasing its conductivity. In a more preferred embodiment with respect to improving the reduction of insulation resistance and dielectric loss, the metal dopant for the B position is Mn.

[0040] As described above, the material according to the present invention is characterized by advantageous piezoelectric functionality within a high temperature range (i.e., at operating temperatures exceeding 250°C, usually up to at least 500°C).

[0041] Preferably, the material according to the invention has a piezoelectric constant d (associated with the change in length (longitudinal effect) along the electric field and the poling axis) which is greater than 50 pC / N, more preferably greater than 60 pC / N, particularly preferably greater than 70 pC / N, determined in each case according to EN50324. 33 has. Usually, the piezoelectric constant d 33 is between 50 pC / N and 110 pC / N, for example between 60 and 100 pC / N.

[0042] Furthermore, the material is preferably suitable for permanent use at a maximum operating temperature of at least 450 °C, more preferably at least 500 °C, particularly preferably at least 550 °C.

[0043] The Curie temperature T of the functional ceramic that can be determined according to EN50324 c is preferably at least 500 °C, more preferably between 550 °C and 640 °C.

[0044] The dielectric constant ε defined as the ratio of the absolute dielectric constant of the material to the dielectric constant in a vacuum (ε0 = 8.85·10 -12 F / m) is preferably between 100 and 500, for example between 180 and 340.

[0045] The dielectric loss factor tanδ of the material that can be determined by small-signal measurements is preferably 0.05 or less, more preferably 0.04 or less, for example between 0.01 and 0.03.

[0046] The invention also relates to a process for manufacturing the above-described material having piezoelectric functionality, (1) mixing a combination of raw materials containing Ag, Bi, Pb and / or Ba, Fe, Ti, and O, and optionally grinding the combination of raw materials; (2) heat-treating the mixed and optionally ground combination of raw materials so that x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1, and M is selected from Pb and / or Ba, with the basic composition Ag x Bi y M z Fe vTi w To provide a perovskite material having including

[0047] In a preferred embodiment, the combination of raw materials includes Ag, Bi, Pb, Ba, Fe, Ti, and O such that M in the basic composition includes both Pb and Ba. In a more preferred embodiment, M is only Pb.

[0048] The manufacturing process according to the present invention can include further process steps, for example, as shown in FIG. 1.

[0049] Generally, the process starts with the provision and weighing of raw materials (which may have dopants in some cases). The starting raw materials are not particularly limited and may include metal oxides, carbon chlorides, hydroxides, halides, or other salts. Preferably, the combination of raw materials includes one or more compounds selected from Bi2O3, Fe2O3, TiO2 and PbTiO3, and / or BaTiO3, and Ag2O, AgF, AgCl, AgBr, AgI, AgNO3, AgCNO, AgN3, Ag2S, and AgOH. Regarding the advantageously low water solubility of the individual raw materials, the combination of raw materials includes one or more compounds selected from Bi2O3, Fe2O3, TiO2 and PbTiO3, and / or BaTiO3, and Ag2O, AgCl, AgBr, AgI, AgCNO, AgN3, Ag2S, and AgOH. In a particularly preferred embodiment, Ag2O is used as the silver-containing raw material (solubility L in water at 25 °C = 0.025 g / l). Composition Ag with x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1 x Bi y M z Fe v N w Other raw materials (such as metal oxides, for example, WO3 or MoO3) can be added as needed, provided that they do not inhibit the formation of the perovskite structure having

[0050] In contrast to known processes that rely on the use of raw materials with significant hygroscopic properties (such as potassium compounds), the process according to the invention enables simple and constant accurate weighing of the raw materials and does not require any additional means (for example, preliminary drying and / or weighing in a protective gas atmosphere).

[0051] Subsequently, the combination of raw materials is mixed in a dry state or in a liquid medium and, if necessary, ground, whereby an aqueous medium (such as water) can advantageously be used as the liquid mixing and / or grinding medium. By minimizing or eliminating the use of organic solvents, it is possible to improve the consideration for the process environment, particularly in the upscaling of the manufacturing process, and to reduce the requirements for labor safety and laboratory safety without impairing the product quality and consistency.

[0052] The firing of the combined raw materials that have been mixed and optionally ground enables the provision of a perovskite material having the composition Ag x Bi y M z Fe v N w O3, where x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1, M is selected from Pb and / or Ba, and N is selected from Ti and / or Zr. It should be noted that the firing can be carried out either before or after grinding, and a coarse grinding step and an ultrafine grinding step can also be interposed. The firing conditions are not particularly limited and can be appropriately adjusted by those skilled in the art. The firing is usually carried out at a temperature above 600 °C to about 900 °C.

[0053] Subsequent further treatment of the obtained fired product may be carried out according to known methods. For example, the fired product can be slurried in a liquid (preferably aqueous) medium and formed into a foil, which can then be supplied to a multi-layer process (including, for example, printing, laminating, laminating, and / or separating) before sintering of the material. Alternatively, the fired product can be subjected to a "simultaneous sintering" process in which, as described in, for example, German Patent Application Publication No. 10234787 C1, a green electrode is provided on the foil, laminated to form a piezoelectric element, and then sintered with the internal electrode in a single process step. Another processing option is that the fired product is slurried or plasticized in a liquid, preferably aqueous medium, homogenized with a suitable binder, and then processed by spray granulation and subsequent compression molding before the molding material is sintered. Alternatively, the fired product may be finely pulverized (as shown in FIG. 1) and then granulated and compression molded.

[0054] The sintering conditions are not particularly limited and may be appropriately selected by those skilled in the art. Sintering is usually carried out at a temperature of at least 850 °C, preferably 950 °C or higher.

[0055] The sintered material may be subjected to mechanical treatment (including, for example, grinding and / or cutting), contact, poling (for example, by applying a DC electric field of about 2 to 10 kV / mm at a temperature of 20 to 150 °C), and electrical measurement in order to provide a piezoelectric ceramic material according to known methods.

[0056] A further embodiment of the present invention relates to a piezoelectric device comprising a compound having the perovskite structure described above or a material having the piezoelectric functionality described above.

[0057] The piezoelectric device can be a piezoelectric actuator, a piezoelectric sensor, or a piezoelectric transformer. Typically, the piezoelectric device includes a compound according to the present invention having a perovskite structure, or a material according to the present invention having piezoelectric functionality in a piezoelectric ceramic body, and at least two electrodes.

[0058] Piezoelectric ceramic bodies may be designed as shaped bodies (usually mechanically hydraulically pressed) in the form of, for example, disks, plates, rods, hemispheres, or rings.

[0059] The piezoelectric material and / or electrodes may be formed as a laminated structure. A laminated piezoelectric device may have a plurality of internal electrode layers and a plurality of piezoelectric layers, each electrode layer being laminated or layered alternately with each respective piezoelectric layer, and at least one of the plurality of piezoelectric layers comprising a compound having a perovskite structure according to the present invention or a material having piezoelectric functionality according to the present invention. Further, such a laminated structure may optionally include additional layers such as one or more buffer layers, substrate layers, conductive portions, and / or insulating layers. The thickness and area of the piezoelectric layers, as well as the number of layers, may be selected according to the intended use of the laminated piezoelectric device.

[0060] In a further embodiment, the piezoelectric device may include, for example, a driver circuit, a current monitoring circuit, and switching means, as disclosed in, for example, German Patent Application Publication No. 102015101817 A1.

[0061] The fields of application of the piezoelectric device according to the present invention are by no means limited and include ultrasonic cleaning, ultrasonic processing, sonar technology, sensor technology, actuator technology, material testing, medical diagnosis and treatment, the automotive industry, aerospace, mechanical engineering, building services, ignition systems, household appliances, and audio applications.

Example

[0062] Example According to the process steps schematically depicted in FIG. 1, a perovskite composition Ag where x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1 x Bi y Pb z Fe v Ti wVarious exemplary piezoelectric functional ceramics based on O3 were manufactured as test piece disks having dimensions of 6.5 mm × 1.0 mm (see Table 2). The individual compositions are shown in Table 1 below.

[0063]

Table 1

[0064] For this purpose, the raw materials Ag2O, Bi2O3, PbTiO3, Fe2O3, and TiO2 were weighed, mixed, and milled in a 1 l drum for 4 hours (mixed 4:1 in demineralized water, ZrO2 milling beads). The particle size after milling was determined using a laser particle size analyzer at d 10 = 0.7 μm, d 50 = 1.5 μm, and d 90 = 3.5 μm. The samples were dried at 120 °C for 24 hours and granulated using a mesh sieve (500 μm). For firing, the samples were filled into an Al2O3 crucible and fired in air in a resistance furnace (60 minutes at 200 °C, 600 minutes at 750 °C, and 180 minutes at 950 °C). The cooled samples were subjected to phase analysis via XRD, by which the presence of non-perovskite heterophases could be excluded. The fired product was finely milled in a 1 l drum (d 10 = 0.7 μm, d 50 = 1.5 μm, and d 90 = 3.5 μm) for 4 hours, dried at 120 °C for 24 hours, sieved using a mesh sieve (500 μm), and then granulated after the addition of 0.8 wt% of PAF (bulk density d Bulk = 2.5 g / cm 3 ). By uniaxial dry pressing (pressing force 34 kN), a diameter of 12 mm, a height of 30 mm, and a bulk density of 5.2 g / cm 3A round cylinder with a bulk density of was obtained. Subsequently, the compacts were sintered according to the conditions listed in Table 1, ground into a round shape (d = 6.5 mm), and cut into disks (d = 6.5 mm, h = 1.0 mm) with a saw. For ceramographic analysis, the sintered disks were ground, polished, and heat-treated at 950 °C for 2 hours in a resistance furnace. The particle sizes in the ceramic microstructure were imaged by an optical microscope and quantified by cross-sectional line measurements and Saltykov analysis (see Table 2).

[0065]

Table 2

[0066] Figures 2a and 2b show examples of ceramographic images of sintered samples B and C. Subsequently, the samples were coated with Ag paste, fired at 850 °C, cooled to room temperature, and then subjected to a poling process (6.5 kV / mm for 15 minutes at 25 °C in oil).

[0067] Polarization materials (cylinders with dimensions d = 6.5 mm, h = 7.0 mm) were investigated for their piezoelectric and dielectric properties using an impedance analyzer. The results are summarized in Table 3.

[0068]

Table 3

[0069] The data shows that the materials according to the present invention advantageously have a high Curie temperature T c (550 °C to 650 °C) and, in combination, a high piezoelectric constant d 33 (higher than 70 pC / N).

[0070] To estimate the maximum operating temperature, the thermal aging stability of an exemplary ceramic was tested in a further series of tests. For this purpose, the samples were aged at different temperature levels starting from 300 °C for 20 hours in each case, and for each aging temperature T AUp to the piezoelectric constant d of the sample (a cylinder having dimensions d = 6.5 mm and h = 7.0 mm) 33 was determined to be at least 60% of the initial value (determined at room temperature). The results of these aging tests are listed in Table 4.

[0071]

Table 4

[0072] The data obtained indicate that the perovskite compound according to the present invention enables the provision of a functional ceramic having excellent piezoelectric and dielectric properties at high temperatures.

Claims

1. Basic composition Ag x Bi y M z Fe v N w O ３ A compound having a perovskite structure, characterized in that it has x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1, M is selected from Pb and / or Ba, and N is selected from Ti and / or Zr.

2. A compound having a perovskite structure according to claim 1, wherein x, y, z, v, and w satisfy ０．０１≦x≦０．２０ ０．５０≦y≦０．８０ ０．０５≦z≦０．５０ ０．５０≦v≦０．７０ ０．３０≦w≦０．５０

3. A compound having a perovskite structure according to any one of claims 1 or 2, wherein x, y, z, v, and w satisfy ０．０２≦x≦０．１４ ０．５６≦y≦０．７６ ０．１０≦z≦０．４２ ０．５４≦v≦０．６２ ０．３８≦w≦０．４６

4. The compound having a perovskite structure according to any one of claims 1 to 3, wherein the compound has a Goldschmidt perovskite structure tolerance factor t in the range of 0.820 to 0.880, preferably in the range of 0.840 to 0.

860.

5. Ag ＋ and Bi ３＋ occupy the position A within the underlying perovskite basic structure ABO ３ A compound having the perovskite structure according to any one of claims 1 to 4, wherein the compound occupies the position A within the underlying perovskite basic structure ABO

6. Fe ３＋ and Ti ４＋ occupy the position B in the underlying perovskite basic structure ABO ３ A compound having the perovskite structure according to any one of claims 1 to 5.

7. A material having piezoelectric functionality, characterized in that the material comprises a perovskite material containing the compound according to any one of claims 1 to 6.

8. The material according to claim 7, wherein the material consists of a pure perovskite material with respect to X-rays without X-ray detectable non-perovskite heterophases.

9. The perovskite material does not contain a perovskite phase having a chemical formula (Bi a K １－a )TiO ３ with 0.4 ≤ a ≤ 0.6, and the perovskite material preferably does not contain potassium ions. The material according to any one of claims 7 or 8.

10. The material according to any one of claims 7 to 9, wherein the perovskite material is doped with manganese (Mn).

11. The material has a piezoelectric functionality at an operating temperature of up to 500 °C, preferably greater than 50 pC / N, more preferably greater than 60 pC / N (for a change in length along the electric field and the poling axis (longitudinal effect)) at an operating temperature of up to 500 °C piezoelectric constant d ３３ The material according to any one of claims 7 to 10, having

12. A method for manufacturing a material having piezoelectric functionality according to any one of claims 7 to 11, comprising: (1) mixing a combination of raw materials containing Ag, Bi, Pb and / or Ba, Fe, Ti and / or Zr, and O, and optionally grinding the combination of raw materials; (2) Heat-treat the combined and optionally ground raw materials to obtain the composition Ag x Bi y M z Fe v N w O ３ To provide a perovskite material having the formula, where x + y + z = 0.9 to 1.1 and v + w = 0.9 to 1.1, M is selected from Pb and / or Ba, and N is selected from Ti and / or Zr

13. The method according to claim 12, wherein in step (1), an aqueous medium, preferably water, is used as a mixing and / or grinding medium.

14. wherein the combination of the raw materials is Bi ２ O ３ , Fe ２ O ３ TiO ２ and / or ZrO ２ , and PbTiO ３ and / or BaTiO ３ , and one or more compounds selected from Ag ２ O, AgF, AgCl, AgBr, AgI, AgNO ３ , AgCNO, AgN ３ , Ag ２ S, and AgOH, preferably one or more compounds selected from Ag ２ O, AgCl, AgBr, AgI, AgCNO, AgN ３ , Ag ２ S, and AgOH, particularly preferably Ag ２ O; the method according to any one of claims 12 or 13.

15. A piezoelectric device further comprising a piezoelectric ceramic body containing the compound having a perovskite structure according to any one of claims 1 to 6, or the material having piezoelectric functionality according to any one of claims 7 to 11, and preferably having at least two electrodes.

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