Laminated piezoelectric ceramic component and device including the same

Abstract

To provide a laminated piezoelectric ceramic component capable of maintaining high insulation properties under high temperature and high electric field conditions.SOLUTION: A laminated piezoelectric ceramic component 10 includes a laminate 20 having a plurality of electrodes 12, 13 and piezoelectric ceramic layers 11 containing, as a main component, an alkali niobate-based perovskite-type oxide, the plurality of electrodes 12, 13 being laminated between the piezoelectric ceramic layers. In the piezoelectric ceramic layers 11 of the laminated piezoelectric ceramic component 10, a portion not sandwiched between the laminated electrodes 12, 13 is defined as an inactive layer 21. The thickness of the inactive layer 21 is 25 μm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer piezoelectric ceramic component and a device including the same. [Background technology]

[0002] In recent years, actuators equipped with multilayer piezoelectric ceramic components that are small and can be driven with high displacement even at low voltages have been attracting attention. Typical multilayer piezoelectric ceramic components include PZT-based (lead zirconate titanate) piezoelectric ceramics and internal electrodes containing, for example, Pt or Pd. However, PZT-based piezoelectric ceramics are problematic because they contain lead, which has a negative impact on the environment. Another drawback is that metal materials such as Pt and Pd are expensive.

[0003] Therefore, there is a growing demand for environmentally friendly and low-cost multilayer piezoelectric ceramic components. To address this, lead-free multilayer piezoelectric ceramics have been proposed, in which lead-free materials are used for the piezoelectric ceramic and the internal electrodes are made primarily of Ni, a base metal that is less expensive than Pt and Pd (see, for example, Patent Documents 1 and 2).

[0004] Patent Documents 1 and 2 propose a multilayer piezoelectric ceramic component in which internal electrodes containing Ni as a main component and piezoelectric ceramic layers containing alkali niobate perovskite oxide as a main component are alternately stacked. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5862983 [Patent Document 2] Patent No. 6094682 Summary of the Invention [Problem to be solved by the invention]

[0006] When multilayer piezoelectric ceramic components are used in actuators, they may be required to be used at high temperatures and high electric fields (for example, 100°C, 3 kV / mm). Therefore, multilayer piezoelectric ceramic components that have high insulation properties even under harsh conditions such as high temperatures and high electric fields are desired.

[0007] An object of the present invention is to provide a multilayer piezoelectric ceramic component that can maintain high insulation properties at high temperatures and in a high electric field, and a device including the same. [Means for solving the problem]

[0008] [1] A multilayer piezoelectric ceramic component according to one aspect of the present invention includes a laminate having a plurality of electrodes and piezoelectric ceramic layers containing an alkali niobate perovskite oxide as a main component, the plurality of electrodes being stacked between the piezoelectric ceramic layers, and a portion of the piezoelectric ceramic layer that is not sandwiched between the plurality of stacked electrodes is an inactive layer, and the thickness of the inactive layer is 25 μm or more.

[0009] According to the above arrangement, by setting the thickness of the inert layer to 25 μm or more, it is possible to obtain a multilayer piezoelectric ceramic component that has high insulating properties at high temperatures and in a strong electric field.

[0010] [2] In the multilayer piezoelectric ceramic part according to one aspect of the present invention described in [1], the electrodes may contain nickel as a main component.

[0011] According to the above-described configuration, the multilayer piezoelectric ceramic component can be manufactured at lower cost.

[0012] [3] In the multilayer piezoelectric ceramic part according to one aspect of the present invention described in [1] or [2], the inert layer may have a thickness of 100 μm or more.

[0013] According to the above arrangement, by setting the thickness of the inert layer to 100 μm or more, the insulating properties of the multilayer piezoelectric ceramic component can be further improved.

[0014] [4] In the multilayer piezoelectric ceramic part according to one aspect of the present invention described in [3], the inert layer may have a thickness of 200 μm or more and 2000 μm or less.

[0015] According to the above configuration, the insulating properties of the multilayer piezoelectric ceramic component can be further improved by setting the thickness of the inert layer to 200 μm or more, and the strength of the multilayer piezoelectric element can be prevented from decreasing by setting the thickness of the inert layer to 2000 μm or less.

[0016] [5] In the multilayer piezoelectric ceramic component according to one aspect of the present invention, as described in any one of [1] to [4], the piezoelectric ceramic layer may contain a main phase component containing the alkali niobate perovskite-type oxide and a subphase component containing oxides of manganese and titanium.

[0017] According to the above configuration, by adding oxides of manganese and titanium as subphase components to a piezoelectric ceramic layer having an alkali niobate perovskite oxide as a main phase component, a dense and highly reliable piezoelectric ceramic layer can be obtained.

[0018] [6] In the multilayer piezoelectric ceramic part according to one aspect of the present invention described in [5], the alkali niobate perovskite oxide may contain manganese and titanium.

[0019] According to the above configuration, the alkali niobate perovskite oxide contains manganese, thereby improving the insulating properties of the piezoelectric ceramic layer, and the alkali niobate perovskite oxide contains titanium, thereby improving the piezoelectric properties of the piezoelectric ceramic layer.

[0020] [7] In the multilayer piezoelectric ceramic part according to one aspect of the present invention described in [6], the alkali niobate perovskite oxide may further contain scandium.

[0021] According to the above-mentioned configuration, the alkali niobate perovskite oxide contains scandium, thereby further improving the insulating properties of the piezoelectric ceramic layer.

[0022] [8] Another aspect of the present invention relates to a device including the multilayer piezoelectric ceramic component according to any one of [1] to [7].

[0023] [9] The device described in [8] may be any of an actuator, a haptic, a buzzer, and an ultrasonic sensor.

[0024] A device according to another aspect of the present invention includes a laminated piezoelectric ceramic component that can maintain high insulation properties at high temperatures and high electric fields, and can therefore maintain good performance even in harsh environments such as high temperatures and high electric fields. [Effects of the Invention]

[0025] According to one aspect of the present invention, it is possible to obtain a multilayer piezoelectric ceramic component that can maintain high insulation properties at high temperatures and under high electric fields. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing a cross-sectional configuration of a multilayer piezoelectric ceramic component according to one embodiment. [Figure 2] FIG. 2 is a perspective view showing a schematic configuration of the multilayer piezoelectric ceramic part shown in FIG. [Figure 3] 2 is a schematic diagram for explaining dimensions of a laminate constituting a multilayer piezoelectric ceramic component. FIG. [Figure 4]1 is a schematic diagram showing the configuration of a vertical cross section (a surface cut along the thickness direction) of a multilayer piezoelectric ceramic component fabricated in an example. [Figure 5] FIG. 1 is a schematic diagram showing an actuator as an example of a device. [Figure 6] FIG. 1 is a schematic diagram showing a tablet terminal equipped with haptics as an example of a device. [Figure 7] FIG. 1 is a schematic diagram illustrating a buzzer as an example of a device. [Figure 8] FIG. 1 is a schematic diagram illustrating an ultrasonic sensor as an example of a device. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a multilayer piezoelectric ceramic component 10, which is an example of a multilayer piezoelectric ceramic component, will be described. The multilayer piezoelectric ceramic component 10 is used as a piezoelectric element in devices such as actuators, haptics, buzzers, and ultrasonic sensors.

[0028] (Structure of multilayer piezoelectric ceramic components) Fig. 1 shows a cross-sectional structure of a multilayer piezoelectric ceramic component 10. Fig. 2 shows a schematic external structure of the multilayer piezoelectric ceramic component 10. Fig. 3 shows a schematic structure of a laminate 20 that constitutes the multilayer piezoelectric ceramic component 10.

[0029] The multilayer piezoelectric ceramic component 10 includes a piezoelectric layer (piezoelectric ceramic layer) 11, a plurality of internal electrodes (electrodes) 12 and 13 disposed within the piezoelectric layer 11, and external electrodes 14 and 15. The internal electrodes (electrodes) 12 and 13 are disposed in a stacked state between the piezoelectric layers 11 to form a laminate 20. The surfaces of the internal electrodes 12 and 13 are in contact with the piezoelectric layers 11.

[0030] The piezoelectric layer 11 contains an alkali niobate perovskite oxide as a main component. Here, "containing as a main component" refers to the component that is contained in the largest proportion when the composition of the piezoelectric layer 11 is viewed in terms of volume % (volume ratio).

[0031] The internal electrodes 12 and 13 contain a base metal as a main component. Specifically, the internal electrodes 12 and 13 contain Ni (nickel) as a main component. Here, "containing as a main component" refers to the component that has the largest content when the composition of the internal electrodes 12 and 13 is viewed in terms of volume percent (volume ratio). By having the internal electrodes 12 and 13 contain Ni as a main component, it is possible to manufacture a multilayer piezoelectric ceramic component more cheaply than electrodes that contain other metals (for example, precious metals such as Pt (platinum)).

[0032] The piezoelectric layers 11 and the internal electrodes 12 and 13 are alternately stacked. More specifically, the piezoelectric layers 11 and the internal electrodes 12 and 13 are stacked in the following order: piezoelectric layer 11, internal electrode 12, piezoelectric layer 11, internal electrode 13, piezoelectric layer 11.... One piezoelectric layer 11 (referred to as a single layer 11a) is sandwiched between two internal electrodes 12 and 13 (see FIG. 1).

[0033] The external electrodes 14 and 15 are arranged on the outer surface of the laminate 20 formed by the piezoelectric layer 11 and the internal electrodes 12 and 13. For example, the external electrode 14 is arranged on one side of the laminate 20, which has a substantially rectangular parallelepiped shape. Moreover, the external electrode 15 is arranged on one side of the laminate 20 opposite to the side on which the external electrode 14 is arranged.

[0034] Of the two internal electrodes 12 and 13 in contact with the single layer 11a, one end of one internal electrode (internal electrode 12 in the example shown in FIG. 1) is connected to one external electrode 14, and one end of the other internal electrode (internal electrode 13 in the example shown in FIG. 1) is connected to the other external electrode 15. When a voltage is applied between the two external electrodes 14 and 15, each single layer 11a expands and contracts, causing the entire multilayer piezoelectric ceramic component 10 to expand and contract.

[0035] In this embodiment, in the piezoelectric layer 11 forming the laminate 20, the portion that is not sandwiched between the stacked internal electrodes 12 and 13 is called an inactive layer 21, and the portion that is sandwiched between the stacked internal electrodes 12 and 13 is called an active layer 22. In this embodiment, the inactive layer 21 is provided in each of the uppermost and lowermost layers of the laminate 20 (see FIG. 3). However, in another embodiment, the inactive layer 21 may be provided in only one of the uppermost and lowermost layers of the laminate 20.

[0036] (Composition of piezoelectric layer) Next, we will explain the composition of the piezoelectric layer 11. As described above, the piezoelectric layer 11 contains alkali niobate perovskite oxide as a main component.

[0037] More specifically, the piezoelectric layer 11 contains a main phase component containing an alkali niobate perovskite oxide and a subphase component containing oxides of manganese and titanium. The main phase component forms a main phase in the piezoelectric layer 11. The subphase component forms a subphase in the piezoelectric layer 11. Within the piezoelectric layer 11, a small amount of the subphase exists mixed in the main phase, which serves as the base.

[0038] The detailed structure of the alkali niobate perovskite oxide, which is the main phase component, is described below. The piezoelectric layer 11 contains, as its main component, an alkali niobate perovskite oxide having piezoelectric properties. The alkali niobate perovskite oxide has a perovskite structure. Metal oxides with a perovskite structure are generally represented by the composition formula ABO3 and are composed of a metal element located at the A site, a metal element located at the B site, and oxygen. In an ideal perovskite structure, 12 oxygen atoms are coordinated around the metal element at the A site, and 6 oxygen atoms are coordinated around the metal element at the B site, with this structure repeating periodically to form a crystal.

[0039] The alkali niobate perovskite oxide of this embodiment preferably contains at least one alkali metal (potassium (K), sodium (Na), lithium (Li), etc.) as an alkaline component at the A site, and particularly preferably contains at least one of potassium (K) and sodium (Na). It also preferably contains niobium (Nb) at the B site. It may also contain an alkaline earth metal (at least one of calcium (Ca), strontium (Sr), barium (Ba), etc.) as an alkaline component at the A site. The effects of the present invention can also be achieved even if some of the alkaline component is located at the B site or niobium is located at the A site.

[0040] It should be noted that the piezoelectric layer 11 does not contain lead (Pb), and therefore the above-described composition forming the piezoelectric layer 11 is also called a lead-free piezoelectric composition.

[0041] Preferably, the alkali niobate perovskite oxide is represented by the following composition formula (1).

[0042] (A1aM1b)c(Nbd1Mnd2Tid3Zrd4Scd5)O3+e ···(1)

[0043] In composition formula (1), the element Nb is niobium. In composition formula (1), the element A1 is at least one of alkali metals Li (lithium), Na (sodium), and K (potassium). In composition formula (2), the element M1 is at least one of alkaline earth metals Ba (barium), Ca (calcium), and Sr (strontium).

[0044] In the above composition formula (1), the elements A1 and M1 are arranged at the A site of the perovskite structure, and Nb (niobium), Mn (manganese), Ti (titanium), and Zr (zirconium) are arranged at the B site.

[0045] As the values of the coefficients a to e in the above compositional formula (1), among the values for which the perovskite structure is established, values preferable from the viewpoints of the electrical properties or piezoelectric properties of the lead-free piezoelectric composition are selected.

[0046] Specifically, the coefficients a and b satisfy 0 < a < 1, 0 < b < 1, and a + b = 1, and a = 0 (i.e., a composition containing no alkali metal) and b = 0 (i.e., a composition containing neither Ba, Ca, nor Sr) are excluded.

[0047] The coefficient c with respect to the entire A site satisfies 0.80 < c < 1.10, and preferably 0.90 ≤ c ≤ 1.05.

[0048] The coefficients d1, d2, d3, d4, and d5 satisfy 0 < d1 < 1, 0 < d2 < 1, 0 < d3 < 1, 0 ≤ d4 < 1, and 0 ≤ d5 < 1. Compositions with d1 = 0 (composition containing no Nb), d2 = 0 (composition containing no Mn), and d3 = 0 (composition containing no Ti) are excluded. The coefficient d4 of Zr may be zero (i.e., a composition containing no Zr). The coefficient d5 of Sc may be zero (i.e., a composition containing no Sc).

[0049] Incidentally, the coefficient d1 of Nb is preferably 0.830 ≤ d1 ≤ 0.959. The coefficient d2 of Mn is preferably 0.001 ≤ d2 ≤ 0.10. The coefficient d3 of Ti is preferably 0.005 ≤ d3 ≤ 0.10. The coefficient d4 of Zr is preferably 0 ≤ d4 ≤ 0.20. Also, it is preferable that d1 + d2 + d3 + d4 + d5 = 1. Among the coefficient 3 + e of oxygen, the coefficient e is a positive or negative value indicating oxygen deficiency or excess with respect to the coefficient of oxygen which is usually 3. The coefficient 3 + e of oxygen can take a value for which the main phase constitutes a perovskite oxide. A typical value of the coefficient e is e = 0, and preferably 0 ≤ e ≤ 0.1. The value of the coefficient e can be calculated from the electrical neutrality condition of the composition of the main phase. However, as the composition of the main phase, a composition slightly deviated from the electrical neutrality condition can also be tolerated.

[0050] The piezoelectric layer 11 can obtain higher piezoelectric properties and insulation properties by containing the alkali niobate perovskite oxide represented by the above compositional formula (1).

[0051] Specifically, the alkali niobate perovskite-type oxide preferably contains Mn and Ti. When a predetermined amount of Mn is added, Mn solid-solves in the Nb site as an acceptor and can form oxygen vacancies, thus improving the insulation property. Also, when a predetermined amount of Ti is added, the crystal structure changes and the piezoelectric properties are considered to be improved.

[0052] In the above compositional formula (1), more preferably, d5 = 0 (a composition not containing Sc) is excluded. That is, it is more preferable that 0 < d5 < 1. Even more preferably, the coefficient d5 of Sc is 0.0002 ≦ d5 ≦ 0.10.

[0053] Thus, in the compositional formula (1), when Sc is added, Sc acts as an acceptor and the generation of carriers is suppressed, so it is considered that the insulation property can be further improved.

[0054] Even more preferably, the alkali niobate perovskite oxide is represented by the following compositional formula (2).

[0055] (Ka1Naa2Lia3Bab1Cab2Srb3)c(Nbd1Mnd2Tid3Zrd4Scd5)O3+e ···(2)

[0056] Compositional formula (2) is equivalent to compositional formula (1), where a1 + a2 + a3 = a and b1 + b2 + b3 = b. The coefficient a1 of K is 0 < a1 ≤ 0.7 (preferably, 0.095 ≤ a1 ≤ 0.665), the coefficient a2 of Na is 0 < a2 ≤ 0.9 (preferably, 0.285 ≤ a2 ≤ 0.855), and the coefficient a3 of Li is 0 ≤ a3 ≤ 0.2 (preferably, 0 ≤ a3 ≤ 0.1). Also, the coefficient b1 of Ba is 0 ≤ b1 ≤ 0.2 (preferably, 0 ≤ b1 ≤ 0.1), the coefficient b2 of Ca is 0 ≤ b2 ≤ 0.2 (preferably, 0 ≤ b2 ≤ 0.1), and the coefficient b3 of Sr is 0 ≤ b3 ≤ 0.2 (preferably, 0 ≤ b3 ≤ 0.1). By setting the coefficients a and b within such ranges, it is considered that the crystal structure can be further optimized and the piezoelectric properties can be further improved.

[0057] Furthermore, in the alkali niobate perovskite-type oxide represented by the above compositional formula (1) or compositional formula (2), the content ratio of Sc to Ti (Sc / Ti) is preferably 0.004 or more and 8 or less in terms of molar ratio. When the content ratio of Sc to Ti is within such a range, it is considered that a piezoelectric layer 11 excellent in piezoelectric properties and insulation properties under high-temperature conditions can be obtained.

[0058] Also, the alkali niobate perovskite oxide according to the present embodiment may contain other elements as needed. For the purposes of improving piezoelectric and insulation properties, controlling sintering temperature, suppressing crystal grain growth, etc., for example, a composition containing at least one of Ta, Ni, Cu, V, Cr, Fe, Co, Zn, Y, Mo, Ru, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, W, Re, Os, Ir, Ag, Si may be added.

[0059] Next, the detailed structure of the subphase component contained in the piezoelectric layer 11 will be described. The alkali niobate perovskite oxide, which is the main component of the piezoelectric layer 11, has a cubic particle shape, which makes it easy for voids to form in the layer, making it difficult to densify the piezoelectric layer. Therefore, it is preferable that the piezoelectric layer 11 contains metal oxide particles as the subphase component. By including metal oxide particles as the subphase component in the piezoelectric layer 11, which is mainly composed of alkali niobate perovskite oxide, the subphase component fills the voids in the main component of the piezoelectric ceramic layer, resulting in a denser and more reliable piezoelectric layer 11.

[0060] The subphase component is preferably contained in the piezoelectric layer 11 at a ratio of 0.1 volume % to 20 volume %, and more preferably at a ratio of 0.5 volume % to 5 volume %.

[0061] The metal oxide particles serving as the subphase component are preferably oxides containing Mn (manganese), for example (manganese-containing oxides). This allows for a denser and more reliable piezoelectric ceramic layer to be obtained. The manganese-containing oxide may be an MnOx oxide such as MnO, MnO2, or Mn3O4, or may contain elements other than manganese, such as an Mn-Ti-O-based oxide (e.g., MnTi2O4, Mn2TiO4, or MnTiO3-based oxide) or an Mn-Nb-O-based oxide (e.g., Mn4Nb2O9 or MnNb2O6-based oxide). Among these, an Mn-Ti-O-based oxide is preferred. The Mn-Ti-O-based oxide has a good affinity with the alkali niobate-based perovskite oxide serving as the main phase component, allowing for a highly reliable piezoelectric layer 11 to be obtained. Therefore, by including Mn-Ti-O-based oxide as a subphase component in the piezoelectric layer 11 whose main component is alkali niobate-based perovskite oxide, it is possible to obtain a denser and more reliable piezoelectric layer 11.

[0062] The Mn—Ti—O-based oxide is represented by the following composition formula (3), for example.

[0063] MnTiOy (3)

[0064] In the above compositional formula (3), the coefficient y satisfies 2 ≤ y ≤ 8. The Mn-Ti-O-based oxide preferably has a spinel-type structure or an inverse spinel-type structure. For example, as the Mn-Ti-O-based oxide, MnTi2O4 and Mn2TiO4 are preferable.

[0065] Also, as long as the structure can be maintained and the change in the properties of the compound is within an acceptable range, it may deviate from the above standard numerical range. For example, the Mn-Ti-O-based oxide may have a structure represented by the following compositional formula (A) or compositional formula (B).

[0066] Mn f Ti 2g O 4±j (A) Mn 2h Ti i O 4±j (B) In the above compositional formulas (A) and (B), the coefficients f, g, h, and i are respectively 0.80 < f < 1.2, 0.8 < g < 1.2, 0.8 < h < 1.2, and 0.8 < i < 1.2, and the coefficient j is a value indicating oxygen deficiency or excess.

[0067] Also, other elements may be contained as necessary. For example, it is possible to contain elements such as Na, K, Zr, Ba, Ca, Sr, Ni, Cu, Ag, and Sc.

[0068] Also, the Mn oxide in the Mn-Ti-O-based oxide can further improve the insulating property of the secondary phase by containing Sc (scandium) in a proportion of 0.05 mol% or more and 5 mol% or less in addition to Mn (manganese).

[0069] Also, there may be a plurality of types of manganese-containing oxides in the manganese-containing oxide. Further, the secondary-phase oxide may contain an oxide other than the manganese-containing oxide.

[0070] (Regarding the dimensions of the multilayer piezoelectric ceramic component) Next, a description will be given of an example of the dimensions of the multilayer piezoelectric ceramic component 10. The overall dimensions of the multilayer piezoelectric ceramic component 10 can be set appropriately by the manufacturer based on the application of the multilayer piezoelectric ceramic component 10, the dimensions and specifications of the device that includes the multilayer piezoelectric ceramic component 10, and the like.

[0071] Fig. 3 shows the schematic configuration and dimensions of a laminate 20 according to one embodiment. Fig. 4 shows the schematic configuration and dimensions of a multilayer piezoelectric ceramic component 10 according to one embodiment. The dimensions shown in Figs. 3 and 4 are examples and are not intended to be limiting.

[0072] The laminate 20 has, for example, a rectangular parallelepiped shape having a length L, a width W, and a height H. For example, the length L may be in the range of 5 mm to 120 mm, and the width W may be in the range of 5 mm to 120 mm. The height H is determined appropriately depending on the thickness t1 of the inactive layer 21, the thickness t2 of the monolayer 11a, and the number of monolayers 11a stacked.

[0073] The thickness t1 of the inactive layer 21 is 25 μm or more. By setting the thickness t1 of the inactive layer 21 in this manner, a multilayer piezoelectric ceramic component 10 having high insulating properties at high temperatures and high electric fields can be obtained. Specifically, as confirmed in the examples described later, the component exhibits excellent insulating properties at high temperatures of, for example, about 100°C and high electric fields of, for example, about 3 kV / mm. Furthermore, the component exhibits excellent piezoelectric properties at high electric fields of, for example, about 3 kV / mm.

[0074] The thickness t1 of the inert layer 21 is preferably 100 μm or more. By setting the thickness t1 of the inert layer 21 in this manner, the insulating properties of the multilayer piezoelectric ceramic component 10 can be further improved.

[0075] The thickness t1 of the inactive layer 21 is more preferably in the range of 200 μm to 2000 μm. By making the thickness t1 of the inactive layer 21 200 μm or more, the insulating properties of the multilayer piezoelectric ceramic component 10 can be further improved. Furthermore, if the inactive layer 21 is too thick, residual stress generated after firing increases, reducing strength, so the thickness t1 is preferably 2000 μm or less.

[0076] The thickness t2 of the monolayer 11a forming the active layer 22 can be, for example, within a range of 5 μm to 300 μm. By setting the thickness t2 of the monolayer 11a in this manner, a laminate having both insulating and piezoelectric properties can be obtained. The thickness of the monolayer 11a can also be considered the distance between the adjacent internal electrodes 12 and 13. In other words, the thickness t2 of the monolayer 11a can also be considered the distance between the electrodes.

[0077] The number of single layers 11a (number of layers stacked) can be, for example, 2 to 200 (i.e., 2 to 200 layers). By setting the number of single layers 11a stacked in this manner, a laminate having both insulating properties and piezoelectric properties can be obtained.

[0078] The thickness of the internal electrodes 12 and 13 can be set within the range of 0.5 μm to 5 μm, for example. By setting the thickness in this manner, a laminate having both insulating properties and piezoelectric properties can be obtained.

[0079] (Manufacturing method for multilayer piezoelectric ceramic components) Here, an example of a method for manufacturing the multilayer piezoelectric ceramic component 10 will be described.

[0080] First, multiple raw material powders (e.g., K2CO3 powder, Na2CO3 powder, Nb2O5 powder, TiO2 powder, ZrO2 powder, MnCO3 powder, BaCO3 powder, and Sc2O3 powder) necessary for forming the main phase are prepared, and the necessary raw material powders are selected from these and weighed to achieve the desired composition. The raw material powders may be oxides, carbonates, or hydroxides of the elements contained in the main phase components. Ethanol is added to the weighed mixture of the raw material powders, and the mixture is wet-mixed in a ball mill, preferably for 15 hours or more, to obtain a slurry. The resulting slurry is dried, and the resulting mixed powder is calcined, for example, in air at a temperature of 600 to 1100°C for 1 to 10 hours, to obtain a powdered calcined main phase.

[0081] Next, a dispersant, a binder, and an organic solvent (e.g., toluene) are added to the obtained main phase calcined product and subphase calcined product, and the mixture is pulverized and mixed to obtain a slurry. The slurry is then processed into a sheet shape using a doctor blade method or the like to produce a ceramic green sheet. The thickness of the ceramic sheet can be controlled by the blade height of the doctor blade device, and the thickness of the ceramic green sheet that will become the inactive layer 21 and the thickness of each ceramic green sheet that will form the single layer 11a of the active layer 22 can be adjusted.

[0082] Next, an electrode layer that will become the internal electrodes 12 and 13 is formed on one side of the ceramic green sheet using a conductive paste for the internal electrodes, for example, by screen printing. The electrode layer is mainly composed of a base metal such as nickel (Ni). In this embodiment, Ni is used as the main component of the base metal, but other base metals besides Ni (nickel), such as Cu (copper), can also be used as the main component of the base metal, and an alloy of Ni and Cu can also be used. Furthermore, other elements such as Ag (silver), Pd (palladium), and Pt (platinum) can also be included in addition to the main component.

[0083] Then, the plurality of ceramic green sheets with electrode layers formed thereon are stacked so that the electrode layers are exposed alternately from both sides. Ceramic green sheets without electrode layers are stacked on both the front and back sides of the laminate thus obtained, respectively, to obtain a laminate. The resulting laminate is then pressure-bonded to obtain a laminate in which the ceramic green sheets and the electrode layers are alternately stacked.

[0084] In the process of obtaining this laminate, the thickness of the ceramic green sheet that becomes the inactive layer 21 and the thickness and number of each ceramic green sheet that forms the single layer 11a of the active layer 22 can be adjusted to desired values, thereby changing the thickness of the inactive layer 21 and the active layer 22. For example, in Example 5, by using green sheets that will be 100 μm thick for the inactive layer and 50 μm thick for the active layer after firing, the thicknesses can be adjusted to any desired thickness.

[0085] The obtained laminate is cut into a desired shape, and then subjected to a binder removal treatment, for example, by holding it in an N2 atmosphere at a temperature of 200 to 400° C. for 2 to 10 hours.

[0086] The laminate after binder removal is sandwiched between alumina setters and fired for 2 to 10 hours at a temperature of, for example, 1000 to 1200°C in a reducing atmosphere where the pressure is controlled to be one order of magnitude or more reduction-side above the equilibrium oxygen partial pressure of Ni / NO. Then, annealing is performed by holding the laminate in a N2 atmosphere at a temperature of, for example, 600 to 1000°C (specifically, 800°C) for 1 to 10 hours (for example, 5 hours). By sandwiching the laminate between alumina setters and performing annealing after firing, a stable laminate can be obtained.

[0087] After the fired laminate has been polished appropriately, a pair of external electrodes 14 and 15 containing Au are formed on the side surfaces of the laminate by, for example, sputtering. Alternatively, a conductive paste containing Ag, Cu, etc. may be applied and baked at about 600°C to 900°C.

[0088] A pair of external electrodes 14 and 15 are formed facing each other with the laminate interposed therebetween. The laminate with the external electrodes formed thereon is subjected to a polarization process to obtain the multilayer piezoelectric ceramic component 10.

[0089] The above manufacturing method is merely an example, and various other steps and processing conditions can be adopted for manufacturing the multilayer piezoelectric ceramic component 10. For example, if the piezoelectric layer 11 contains a subphase, multiple types of raw material powders necessary for forming the subphase may be prepared, and these raw material powders may be used to appropriately produce powdered subphase calcined powder. The obtained subphase calcined powder may then be appropriately mixed with the main phase calcined powder in a predetermined ratio to form the desired multilayer piezoelectric ceramic component 10.

[0090] (Devices with multilayer piezoelectric ceramic components) The multilayer piezoelectric ceramic component according to this embodiment can be used in various devices that use piezoelectric elements, such as, but not limited to, actuators (see FIG. 5), haptics (see FIG. 6), buzzers (see FIG. 7), and ultrasonic sensors (see FIG. 8).

[0091] The actuator may be configured using a conventional piezoelectric actuator. A more specific configuration of the actuator may be, for example, the configuration described in Patent Document 3 (JP 2023-109208 A). Fig. 5 shows a schematic configuration of an actuator 101 having a multilayer piezoelectric ceramic component 10.

[0092] The haptics configuration can be a conventionally known haptics configuration including a piezoelectric element. Fig. 6 shows a schematic configuration of a tablet terminal 201 having a haptics 102. The haptics 102 includes a multilayer piezoelectric ceramic component 10.

[0093] The buzzer may be configured using a conventionally known piezoelectric buzzer. As a more specific configuration of the sound generating body, for example, the configuration described in Patent Document 4 (JP 2023-90233 A) may be used. FIG. 7 shows a schematic configuration of a buzzer 103 having a multilayer piezoelectric ceramic component 10. The buzzer 103 has a case 110. The multilayer piezoelectric ceramic component 10 (not shown in FIG. 7) that functions as a sound generating body is disposed inside the case 110.

[0094] The ultrasonic sensor can be configured using a conventionally known ultrasonic sensor including a piezoelectric element. Fig. 8 shows a schematic configuration of an ultrasonic sensor 104 having a multilayer piezoelectric ceramic component 10. The ultrasonic sensor 104 has a hollow exterior body 120. The exterior body 120 contains a multilayer piezoelectric ceramic component 10 (not shown in Fig. 8) that functions as a piezoelectric vibrator.

[0095] The device according to this embodiment includes a multilayer piezoelectric ceramic component 10. Specific examples of the device according to this embodiment include an actuator (see FIG. 5), a haptic (see FIG. 6), a buzzer (see FIG. 7), and an ultrasonic sensor (see FIG. 8).

[0096] The device of this embodiment is equipped with a multilayer piezoelectric ceramic component 10 that can maintain high insulation properties at high temperatures and high electric fields, and therefore can maintain good performance even in harsh environments such as high temperatures and high electric fields.

[0097] [Example] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0098] In this example, a plurality of multilayer piezoelectric ceramic components 10 were manufactured with different thicknesses of the inactive layer 21 and the single layer 11a forming the piezoelectric layer 11, and the insulating properties and piezoelectric properties of these components were evaluated.

[0099] (Manufacturing of multilayer piezoelectric ceramic parts) The multilayer piezoelectric ceramic component was manufactured by the following method. The raw material powders for forming the main phase were K2CO3 powder, Na2CO3 powder, Nb2O5 powder, TiO2 powder, ZrO2 powder, MnCO3 powder, BaCO3 powder, and Sc2O3 powder. Each raw material powder was weighed to obtain the composition shown in Table 1. An appropriate amount of ethanol was added to the weighed mixture of raw material powders, and the mixture was wet-mixed in a ball mill for 15 hours to obtain a slurry. The resulting slurry was dried, and the mixed powder obtained after drying was calcined in air at 900°C for 5 hours to obtain a powdered calcined main phase.

[0100] [Table 1]

[0101] MnCO3 powder and TiO2 powder were prepared as raw material powders for forming the subphase. These raw material powders were weighed so that the target composition would be Mn2TiO4. An appropriate amount of ethanol was added to the weighed mixture of raw material powders, and the mixture was wet-mixed in a ball mill for 15 hours to obtain a slurry. The resulting slurry was dried, and the mixed powder obtained after drying was calcined in air at a temperature of 1200°C for 5 hours to obtain a powdered calcined subphase.

[0102] A dispersant, acrylic binder, and toluene were added to the obtained main phase and subphase calcined products, and the mixture was pulverized and mixed to obtain a slurry. The subphase calcined product was added so that the subphase component, Mn2TiO4, was 1.5% by volume relative to 97.5% by volume of alkali niobate perovskite oxide. The slurry was then processed into sheets using a doctor blade method or other methods to produce ceramic green sheets. Ceramic green sheets with various film thicknesses were produced by adjusting the blade height of the doctor blade device.

[0103] Next, an electrode layer that would become the internal electrodes 12 and 13 was formed on the ceramic green sheet by screen printing using a conductive paste for the internal electrodes containing Ni. The thickness of the electrode layer was adjusted so that the thickness of the internal electrodes 12 and 13 after firing would be approximately 2 μm.

[0104] Then, multiple ceramic green sheets with electrode layers formed thereon were stacked so that the electrode layers were exposed alternately from both sides. Ceramic green sheets without electrode layers were further stacked on both the front and back sides of the resulting laminate to obtain a laminate. Thirty-one single layers 11a were stacked. The resulting laminate was then thermocompression bonded to obtain a laminate in which ceramic green sheets and electrode layers were alternately stacked. Green sheets were selected and stacked so that the thickness of the green sheets after firing would be the same as that of each comparative example and each example.

[0105] The obtained laminate was cut into a predetermined shape and then subjected to a binder removal treatment by being held in a nitrogen atmosphere at a temperature of 300°C for 5 hours. The laminate after binder removal treatment was sandwiched between alumina setters and heated at a temperature of 1050°C with an oxygen partial pressure of 10 -12 The sample was fired for 5 hours in a reducing atmosphere of 800°C, and then annealed for 10 hours in a N2 atmosphere at 800°C.

[0106] After the fired laminate 20 had its sides polished appropriately, a pair of external electrodes 14 and 15 containing Au were formed on the sides of the laminate, for example by sputtering, and then the laminate was polarized for 10 minutes at a DC voltage of 4 kV / mm and a temperature of 50°C to obtain a laminated piezoelectric ceramic component 10.

[0107] Figure 3 shows the schematic configuration and dimensions of the fabricated laminate 20. Figure 4 shows the schematic configuration and dimensions of the fabricated multilayer piezoelectric ceramic component 10. The laminate 20 has a roughly rectangular parallelepiped shape with a length L of 8 mm, a width W of 8 mm, and a height H.

[0108] In each example and comparative example, the thickness t1 of the inactive layer 21 and the thickness t2 of the monolayer 11a were varied. In addition, in all examples and comparative examples, the number of monolayers 11a was 31. As a result, the height H of the laminate 20 varied in each example and comparative example.

[0109] Table 2 shows the thickness t1 of the inactive layer 21 and the thickness t2 of the monolayer 11a in each example and each comparative example.

[0110] (Composition analysis of the main phase) The piezoelectric layer 11 of the laminate 20 of each example and comparative example was analyzed using an electron probe microanalyzer (EPMA). Specifically, an image of each laminate 20 was taken at 5000x magnification, and quantitative analysis was performed on three arbitrary crystal grains from the obtained image. The composition of the main phase of each example and comparative example was then determined from the average of the quantitative values ​​of each element in the crystal grains at the three points. As a result, it was confirmed that the compositions were as shown in Table 1.

[0111] (Thickness measurement of single layer and inactive layer) The cross section of the laminate 20 of each example and comparative example was mirror-polished, and a backscattered electron image was taken at 100x magnification using a scanning electron microscope (SEM). The inactive layer 21 was imaged in a 500 μm × 500 μm area, with the center at the center of the top and bottom layers of the laminate 20, and the single layer 11a was imaged in a 500 μm × 500 μm area, with the center at the center of the 1st, 16th, and 31st layers of the 31-layer structure of the single layer 11a. The contrast in the backscattered electron image allows easy distinction between the piezoelectric ceramic layers (single layers and inactive layers) and the internal electrodes.

[0112] The thickness t1 of the inactive layer 21 was determined as the average value of the thickness of the top layer and the thickness of the bottom layer at the center. The thickness t2 of the single layer 11a was determined as the average value of the distance between the internal electrode 12 and the internal electrode 13 at the center, measured for the 1st, 16th, and 31st layers of the single layer 11a. Table 2 shows the thicknesses t1 and t2 obtained by this calculation method for each example and comparative example.

[0113] (Evaluation of piezoelectric properties) For the multilayer piezoelectric ceramic parts 10 of each example and each comparative example, a laser Doppler vibrometer was used to measure the longitudinal displacement S of the laminate using unipolar driving (specifically, a positive electric field with a maximum electric field Emax of +3 kV / mm was applied to the sample at room temperature as a sine wave with a frequency of 0.1 Hz), and the S / E value for each electric field was calculated by dividing the displacement S by the electric field E. The results are shown in Table 2.

[0114] The obtained S / E value is an index of the displacement characteristics (piezoelectric characteristics). A larger S / E value indicates better piezoelectric characteristics. It was confirmed that the comparative example in which the thickness t1 of the inactive layer 21 was smaller (i.e., t1 = 16 μm) had a smaller S / E value than the examples. Furthermore, it was confirmed that the S / E value was 300 pm / V or more in Examples 1-12 in which the thickness t1 of the inactive layer 21 was 28 μm or more.

[0115] (insulation resistance measurement) The insulation resistance (Ω m) of the multilayer piezoelectric ceramic component 10 of each example and comparative example was measured. Specifically, the multilayer piezoelectric ceramic component 10 was placed in silicone oil at 100°C, a DC voltage of 3 kV / mm was applied, and the insulation resistance (Ω m) was measured after 1 minute. The results are shown in Table 2.

[0116] The insulation resistance measurement was judged according to the following criteria. Table 2 shows the judgement results as "Good" or "Poor." 〇 (Good): Insulation resistance (Ω m) is 1×10 5 (Ω m) or more × (indicates failure): Insulation resistance (Ω m) is 1×10 5 Less than (Ω·m)

[0117] It was confirmed that Examples 1-12, in which the thickness t1 of the inactive layer 21 was 28 μm or more, exhibited good insulating properties. It was also confirmed that Examples 4-7, in which the thickness t1 of the inactive layer 21 was 100 μm or more, exhibited improved insulating properties compared to Examples 1-3. It was also confirmed that Examples 8-10, in which the thickness t1 of the inactive layer 21 was 200 μm or more, exhibited improved insulating properties compared to Examples 4-7.

[0118] The results of Examples 4-6 suggest that the thickness t2 of the single layer 11a does not have a significant effect on the insulation resistance value.

[0119] Table 2 shows whether Sc was added in each example and comparative example, and the Sc content (mol%) in the piezoelectric layer when Sc was added. It was confirmed that Examples 11 and 12, in which Sc was added, had higher insulation resistance values ​​than Example 3, in which the thickness t1 of the inactive layer 21 and the thickness t2 of the monolayer 11a were similar. This result suggests that adding Sc to the main phase of the piezoelectric layer 11 can further improve the insulation properties.

[0120] [Table 2]

[0121] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, configurations obtained by combining the configurations of different embodiments described in this specification are also included in the scope of the present invention. [Explanation of symbols]

[0122] 10: Multilayer piezoelectric ceramic parts 11: Piezoelectric layer (piezoelectric ceramic layer) 11a: Single layer 12: Internal electrode (electrode) 13: Internal electrode (electrode) 14:External electrode 15: External electrode 20: Laminate 21 :Inactive layer 22:Active layer 101: Actuator 102: Haptics 103: Buzzer 104: Ultrasonic sensor

Claims

1. The piezoelectric ceramic layer has a plurality of electrodes and contains an alkali niobate perovskite oxide as a main component. a multilayer piezoelectric ceramic component including a laminate in which the plurality of electrodes are stacked between the piezoelectric ceramic layers, a portion of the piezoelectric ceramic layer that is not sandwiched between the plurality of stacked electrodes is an inactive layer; The thickness of the inert layer is 25 μm or more.

2. 2. The multilayer piezoelectric ceramic part according to claim 1, wherein the electrodes contain nickel as a main component.

3. 2. The multilayer piezoelectric ceramic part according to claim 1, wherein the inert layer has a thickness of 100 [mu]m or more.

4. 4. The multilayer piezoelectric ceramic part according to claim 3, wherein the thickness of the inert layer is 200 μm or more and 2000 μm or less.

5. The piezoelectric ceramic layer is a main phase component containing the alkali niobate perovskite oxide; a subphase component containing oxides of manganese and titanium; 2. The multilayer piezoelectric ceramic component according to claim 1, comprising:

6. 6. The multilayer piezoelectric ceramic component according to claim 5, wherein the alkali niobate perovskite oxide contains manganese and titanium.

7. 7. The multilayer piezoelectric ceramic component according to claim 6, wherein the alkali niobate perovskite oxide further contains scandium.

8. A device comprising the multilayer piezoelectric ceramic component according to any one of claims 1 to 7.

9. The device of claim 8 , wherein the device is one of an actuator, a haptic, a buzzer, and an ultrasonic sensor.

Images