Conductive paste

Abstract

This suppresses Zn deposition in conductive paste containing PZT-Zn particles as a co-material. [Solution] The conductive paste disclosed herein comprises conductive particles, co-material particles, a binder, and an organic solvent. The co-material particles are perovskite-type oxides containing at least Pb, Zr, Ti, and Zn. In the conductive paste disclosed herein, a deposition inhibitor containing Ti and / or Zr is attached to the surface of the co-material particles. With a conductive paste of this configuration, it is possible to suppress the deposition of Zn after firing while suppressing the adverse effect of reduced piezoelectric properties due to the inclusion of impurity elements.

Description

Technical Field

[0001] The technology disclosed herein relates to a conductive paste for laminated piezoelectric components.

Background Art

[0002] Conventionally, laminated piezoelectric components have been widely used in capacitors, actuators, and the like. In such laminated piezoelectric components, piezoelectric layers and internal electrode layers are alternately laminated. Among these, the main component of the piezoelectric layer is a piezoelectric material such as lead zirconate titanate (PZT: Pb(Zr,Ti)O3). On the other hand, the main component of the internal electrode layer is a conductive material such as a metal. In the manufacture of laminated piezoelectric components, after applying a conductive paste containing a conductive material (conductive particles) to the surface of a green sheet (piezoelectric sheet) containing a piezoelectric material, these are fired simultaneously. When such simultaneous firing is performed, the conductive paste is more likely to thermally shrink than the piezoelectric sheet. This difference in thermal shrinkage behavior can cause cracks to occur in the internal electrode layer after firing. For this reason, a ceramic of the same type as the piezoelectric material that is the main component of the piezoelectric layer (such as PZT) is added as a co-material to the conductive paste for laminated piezoelectric components (see Patent Document 1). Thereby, cracks in the internal electrode layer after firing can be suppressed.

[0003] In addition, in the manufacture of laminated piezoelectric components in recent years, low-temperature firing at 1100°C or lower has been considered from the perspective of cost reduction. For example, Patent Document 2 describes that PZT particles containing zinc (Zn) (PZT-Zn particles) can be fired at a low temperature because they have a high mechanical quality factor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conductive pastes containing PZT-Zn particles as a co-material may experience Zn precipitation during firing. This Zn precipitation can induce compositional shifts in the piezoelectric layer, potentially leading to defects such as protrusions on the surface of the piezoelectric layer and a decrease in piezoelectric properties. The technology disclosed herein was developed to solve these problems and aims to provide a technology for suppressing Zn precipitation in conductive pastes containing PZT-Zn particles as a co-material. [Means for solving the problem]

[0006] The conductive paste disclosed herein is a conductive paste for multilayer piezoelectric components comprising conductive particles, co-material particles, a binder, and an organic solvent. The co-material particles of this conductive paste are perovskite-type oxides containing at least Pb, Zr, Ti, and Zn. The conductive paste disclosed herein is characterized in that a deposition inhibitor containing Ti and / or Zr is attached to the surface of the co-material particles.

[0007] The inventors, through various experiments and studies, discovered that attaching Group IV elements such as Ti and Zr to the surface of co-material particles can suppress the deposition of Zn from PZT-Zn particles. While not intended to limit the technology disclosed herein, it is presumed that this deposition suppression effect occurs for the following reasons. First, the deposition suppressing material containing Ti and Zr becomes a metal oxide such as TiO2 and ZrO2 during firing. This metal oxide suppresses excessive melting and sintering of the PZT-Zn particles, thereby suppressing the desorption of Zn from the PZT-Zn particles during firing. Furthermore, since TiO2 and ZrO2 have the characteristic of being highly reactive with Zn, the deposition of Zn that has desorbed from the PZT-Zn particles as a single element can also be suppressed. In the conductive paste disclosed herein, the deposition suppressing material containing Ti and Zr is directly attached to the PZT-Zn particles. This allows the above-mentioned deposition suppression effect to be fully exhibited.

[0008] In addition, PZT-Zn particles are perovskite-type oxides containing Zr and Ti at the B site. If an impurity element different from that of the B site of the PZT-Zn particles is mixed into the conductive paste, the B site may be replaced by the impurity element, or the impurity element may be dissolved in the PZT-Zn particle. The inclusion of these impurity elements can cause a decrease in piezoelectric properties. In contrast, the conductive paste disclosed herein uses the same element as the B site of the PZT-Zn particles as a deposition inhibitor. This prevents a decrease in piezoelectric properties due to the inclusion of impurity elements. As described above, the conductive paste disclosed herein can suppress Zn deposition after firing while suppressing the adverse effect of decreased piezoelectric properties. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an SEM image (5000x magnification) of sample 1. [Figure 2] Figure 2 is an SEM image (5000x magnification) of sample 2. [Figure 3] Figure 3 is an SEM image (5000x magnification) of sample 3. [Figure 4] Figure 4 is an SEM image (5000x magnification) of sample 4. [Figure 5] Figure 5 is an SEM image (5000x magnification) of sample 5. [Figure 6] Figure 6 is an SEM image (5000x magnification) of sample 6. [Figure 7] Figure 7 is an SEM image (5000x magnification) of sample 7. [Figure 8] Figure 8 is an SEM image (5000x magnification) of sample 8. [Figure 9] Figure 9 is an SEM image (5000x magnification) of sample 9. [Figure 10] Figure 10 is an SEM image (5000x magnification) of sample 10. [Figure 11] Figure 11 is an SEM image (5000x magnification) of sample 11. [Modes for carrying out the invention]

[0010] Preferred embodiments of the technology disclosed herein will be described below. Matters other than those specifically mentioned herein that are necessary for carrying out the technology disclosed herein can be carried out based on the contents of this specification and the common technical knowledge of those skilled in the art to which the technology disclosed herein belongs.

[0011] [Conductive paste] The conductive paste disclosed herein comprises conductive particles, co-material particles, a binder, and an organic solvent as its main components. The components of the conductive paste disclosed herein will be described below.

[0012] 1. Conductive particles Conductive particles are inorganic particles with excellent electrical conductivity. Conductive particles become the main component of the internal electrode layer after firing. Conventionally known materials capable of forming the internal electrode layer of multilayer piezoelectric components can be used as conductive particles without particular limitations. Examples of conductive particle materials include nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), aluminum (Al), and tungsten (W). Furthermore, conductive particles may be composite materials (alloys, co-precipitated powders, core-shell particles, etc.) containing multiple of the above-mentioned metallic materials. A suitable example of conductive particles is Ag-Pd composite material. Ag-Pd composite material is particularly suitable as the main component of the internal conductive layer of multilayer piezoelectric components because it can be fired in air and is less expensive than gold, platinum, and palladium. In this context, "Ag-Pd composite material" refers to any material in which Ag and Pd are combined. Examples of Ag-Pd composite materials include alloys containing Ag and Pd, co-precipitated powders, and core-shell particles in which an Ag core is coated with a Pd shell. Furthermore, the conductive paste disclosed herein may contain only one of the aforementioned conductive particles, or it may contain two or more.

[0013] When the total mass of the conductive paste is 100 wt%, the content of the conductive particles is preferably 30 wt% or more, more preferably 35 wt% or more, and particularly preferably 40 wt% or more. As the content of the conductive particles increases, the continuity of the internal conductive layer after firing improves. As a result, high conductivity can be suitably realized. On the other hand, the upper limit value of the content of the conductive particles is preferably 65 wt% or less, more preferably 60 wt% or less, still more preferably 55 wt% or less, and particularly preferably 50 wt% or less. Thereby, the generation of cracks due to the deviation in the thermal shrinkage behavior from the piezoelectric layer can be suppressed. Also, as the content of the conductive particles decreases, the paste handling property and the workability during film formation are improved.

[0014] Also, the average particle diameter of the conductive particles may be 1.6 μm or less, may be 1.4 μm or less, is preferably 1.3 μm or less, more preferably 1.2 μm or less, still more preferably 1.1 μm or less, and particularly preferably 1 μm or less. By using conductive particles with a small average particle diameter, it is possible to contribute to thinning of the internal conductive layer. On the other hand, the lower limit value of the average particle diameter of the conductive particles may be 0.1 μm or more, may be 0.2 μm or more, is preferably 0.3 μm or more, more preferably 0.4 μm or more, still more preferably 0.5 μm or more, and particularly preferably 0.6 μm or more. Thereby, the generation of coarse particles due to aggregation of the conductive particles can be suppressed. In this specification, the "average particle diameter" refers to the particle diameter (D 50 particle diameter) corresponding to 50% cumulative from the small diameter side in the number-based particle size distribution based on the observation image of a scanning electron microscope (SEM).

[0015] Also, the shape of the conductive particles is not particularly limited. For example, the shape of the conductive particles may be spherical or substantially spherical. The average aspect ratio of the conductive particles is typically 1 to 2, preferably 1 to 1.5. Thereby, the viscosity of the paste can be maintained low, and the handling property of the paste and the workability during film formation for forming the conductor film can be improved. Also, the homogeneity of the paste can be improved. In this specification, the "aspect ratio" can be calculated as the ratio of the long diameter to the short diameter of the fine particles observed in the SEM observation image described above. And, the arithmetic mean value of the aspect ratios of 100 or more (for example, 100 to 1000) fine particles can be defined as the "average aspect ratio".

[0016] 2. Co-material particles Co-material particles are added to adjust the thermal shrinkage behavior of the internal electrode layer. Typically, the co-material particles are particles containing the same kind of ceramic as the main component (piezoelectric material) of the piezoelectric layer. By such co-material particles, the generation of cracks due to the deviation of the thermal shrinkage behavior between the piezoelectric layer and the internal electrode layer can be suppressed. However, the component of the co-material particles of the conductive paste does not have to exactly match the piezoelectric material of the piezoelectric layer. That is, the co-material particles may be composed of a ceramic different from the piezoelectric material of the piezoelectric layer as long as the thermal shrinkage behaviors of the piezoelectric layer and the internal electrode layer can be approximated.

[0017] The co-material particles of the conductive paste disclosed herein are perovskite-type oxides containing at least Pb, Zr, Ti, and Zn. Specifically, the co-material particles have a perovskite-type crystal structure represented by the general formula ABO3. And, lead (Pb) is contained in the A site of the perovskite-type crystal structure. On the other hand, zirconia (Zr) and titanium (Ti) are contained as the first elements in the B site, and zinc (Zn) is contained as the second element. In this specification, the co-material particles having such a configuration are referred to as "PZT-Zn particles". Since the PZT-Zn particles contain Zn, they can be easily sintered even at a low firing temperature of 1100 °C or lower.

[0018] The detailed composition of the PZT-Zn particles (the ratios of Pb, Zr, Ti, and Zn) is not limited to the technology disclosed herein. In other words, the PZT-Zn particles used in the technology disclosed herein can be any conventionally known PZT-Zn particles disclosed in International Publication No. 2022 / 153680, etc., without any particular limitation, and therefore a detailed explanation is omitted in this specification.

[0019] Furthermore, when the total mass of the conductive paste is 100 wt%, the content of co-material particles is preferably 5 wt% or more, more preferably 7.5 wt% or more, even more preferably 10 wt% or more, and particularly preferably 12.5 wt% or more. This allows for more effective prevention of cracks in the internal electrode layer. In addition, by adding a certain amount or more of PZT-Zn particles, low-temperature firing of the conductive paste can be achieved more reliably. On the other hand, the upper limit of the content of co-material particles is preferably 25 wt% or less, more preferably 22.5 wt% or less, even more preferably 20 wt% or less, and particularly preferably 17.5 wt% or less. As the amount of PZT-Zn particles added decreases, Zn deposition after firing becomes easier to suppress.

[0020] Furthermore, the average particle size of the co-material particles is preferably 1.6 μm or less, more preferably 1.4 μm or less, even more preferably 1.2 μm or less, and particularly preferably 1.0 μm or less. As the size of the co-material particles decreases, it contributes to thinning the internal conductive layer. The lower limit of the average particle size of the co-material particles is preferably 0.01 μm or more, more preferably 0.02 μm or more, even more preferably 0.03 μm or more, and particularly preferably 0.04 μm or more. As the size of the co-material particles increases, aggregation of the co-material particles can be suppressed, thus preventing the generation of coarse secondary particles.

[0021] 3.Precipitation inhibitor The conductive paste disclosed herein is characterized in that a deposition inhibitor containing Ti and / or Zr is attached to the surface of the co-material particles. During firing, this deposition inhibitor becomes a metal oxide of a group 4 element such as TiO2 or ZrO2. This metal oxide suppresses excessive melting and sintering of the PZT-Zn particles, thereby suppressing the desorption of Zn from the PZT-Zn particles during firing. Furthermore, since TiO2 and ZrO2 have the property of being highly reactive with Zn, the deposition of Zn desorbed from the PZT-Zn particles as a single element can also be suppressed. In the conductive paste disclosed herein, the deposition inhibitor is directly attached to the PZT-Zn particles. This allows the effect of the deposition inhibitor to be suitably exhibited. This deposition inhibitor contains the same element (Ti or Zr) as the B site of the PZT-Zn particles. This prevents a decrease in piezoelectric properties due to the inclusion of impurity elements. As described above, the conductive paste disclosed herein can suppress the adverse effect of reduced piezoelectric properties while also suppressing Zn deposition after firing.

[0022] Furthermore, the precipitation inhibitor will exert its precipitation inhibitory effect on Zn if it adheres to the surface of the co-material particles (PZT-Zn particles). In other words, the precipitation inhibitor only needs to adhere to the particle surface and is not limited to any particular form. An example of the form of the precipitation inhibitor will be described below.

[0023] For example, the precipitation inhibitor may be a particulate material. Experiments have confirmed that this particulate precipitation inhibitor (hereinafter also referred to as "precipitation inhibitor particles") suppresses Zn precipitation after firing by adhering to the surface of the co-material particles. The method for adhering the precipitation inhibitor particles to the co-material particles is not particularly limited, and conventionally known methods can be used as appropriate. For example, the co-material particles and precipitation inhibitor particles can be mixed in the liquid phase before preparing the conductive paste. This causes the precipitation inhibitor particles to adhere to the surface of the co-material particles. As mentioned above, the precipitation inhibitor exerts its precipitation inhibitory effect on Zn by becoming a metal oxide (TiO2 or ZrO2) during firing. However, the precipitation inhibitor particles before firing do not have to be a metal oxide. That is, the precipitation inhibitor particles may be elemental metals such as Ti or Zr, or metal hydroxides such as Ti(OH)4 or Zr(OH)4. Since elemental metals and metal hydroxides become metal oxides by oxidation during firing, they can fully exert their precipitation inhibitory effect on Zn. However, from the viewpoint of more stably exhibiting the precipitation suppression effect, it is preferable that the precipitation suppression particles are metal oxide particles such as TiO2 or ZrO2.

[0024] Furthermore, the average particle size of the precipitation-inhibiting particles is preferably 1000 nm or less, more preferably 500 nm or less, even more preferably 100 nm or less, and particularly preferably 50 nm or less. Because precipitation-inhibiting particles with a small particle size tend to adhere to the surface of the co-material particles, they can stably exhibit a precipitation-inhibiting effect on Zn. On the other hand, the lower limit of the average particle size of the precipitation-inhibiting particles is preferably 1 nm or more, more preferably 5 nm or more, even more preferably 10 nm or more, and particularly preferably 15 nm or more. This suppresses the generation of coarse particles due to aggregation of precipitation-inhibiting particles.

[0025] Another example of a deposition inhibitor is a coating that covers the surface of the co-material particles (hereinafter also referred to as the "deposition inhibitor film"). This deposition inhibitor film has also been confirmed to suppress the deposition of Zn from the co-material particles. The deposition inhibitor film only needs to generate metal oxides (TiO2 or ZrO2) during firing, and the state before firing is not particularly limited. For example, the deposition inhibitor film may be an organometallic compound containing Ti or Zr (Ti resinate, Zr resinate). During firing, this organometallic compound decomposes, with the organic components being burned away and the metal components being oxidized. This allows it to exert a deposition inhibitory effect on Zn. When using an organometallic compound as the deposition inhibitor film, it is preferable to mix the co-material particles and the organometallic compound before preparing the conductive paste. This allows the surface of the co-material particles to be coated with a deposition inhibitor film made of the organometallic compound.

[0026] Furthermore, it is preferable to adjust the amount of precipitation inhibitor added by considering the relationship between the total number of moles of Ti and Zr in the precipitation inhibitor and the number of moles in the PZT-Zn particles. By attaching sufficient Ti and Zr to the Zn in the co-material particles, the precipitation of Zn can be more effectively suppressed. For example, the ratio X / Y of the number of moles of precipitation inhibitor X to the number of moles Y of Zn in the co-material particles may be 0.5 or more, 2 or more, 3 or more, preferably 4 or more, more preferably 4.5 or more, even more preferably 5 or more, and particularly preferably 5.5 or more. This allows for particularly effective suppression of Zn precipitation. On the other hand, the upper limit of the above ratio X / Y is not particularly limited and may be 10 or less, 8 or less, 7.5 or less, 7 or less, or 6.5 or less.

[0027] 4. Binder The binder is a component that binds conductive particles and co-material particles together, as well as the substrate, when the conductive paste is applied to the substrate. Preferably, the resin binder is a component that burns through during the firing of the conductive paste.

[0028] The type of binder is not particularly limited, and one or more conventionally known organic compounds that can be used as binders can be used alone or in appropriate combinations. The binder is typically a thermoplastic resin. However, it may also be a thermosetting resin. Examples of binders include organic polymer compounds such as cellulose resins, polyvinyl acetal resins, polyvinyl alcohol resins, acrylic resins, urethane resins, epoxy resins, phenolic resins, rosin resins, polyester resins, and ethylene resins. Among these, cellulose resins are preferred from the viewpoint of improving burnability during firing and surface smoothness of the internal electrode layer after firing. Cellulose resins encompass linear polymers (cellulose) containing β-glucose as repeating units, and their derivatives in general. Examples of cellulose resins include methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, carboxyethylcellulose, and nitrocellulose. Methylcellulose and ethylcellulose are particularly preferred.

[0029] Furthermore, the binder content, when the total mass of the conductive paste is 100 wt%, is preferably 10 wt% or less, more preferably 7.5 wt% or less, and particularly preferably 5 wt% or less. This suppresses the generation of firing residue. On the other hand, the lower limit of the binder content is preferably 0.5 wt% or more, more preferably 1 wt% or more, and particularly preferably 2.5 wt% or more. This allows the binder's effects (such as improved adhesion and shape stability) to be optimally exhibited.

[0030] 5. Organic solvents Organic solvents are liquid media used to disperse inorganic powders. Organic solvents evaporate upon heating. The type of solvent is not particularly limited, and one or more solvents from among those conventionally known can be used individually or in appropriate combinations. Examples include alcohol-based solvents, ether-based solvents, ester-based solvents, and hydrocarbon-based solvents. Among these, alcohol-based solvents are preferred. Examples of alcohol-based solvents include methanol, sclareol, citronellol, phytol, geranyl linalool, texanol, benzyl alcohol, phenoxyethanol, 1-phenoxy-2-propanol, terpineol, dihydroterpineol, isoborneol, butyl carbitol, and diethylene glycol.

[0031] Furthermore, the organic solvent content of the conductive paste, when the total mass is 100 wt%, is preferably 20 wt% or more, more preferably 25 wt% or more, even more preferably 30 wt% or more, and particularly preferably 35 wt% or more. This imparts appropriate fluidity to the conductive paste, improving workability in forming the internal electrode layer. On the other hand, the upper limit of the organic solvent content is preferably 60 wt% or less, more preferably 50 wt% or less, and particularly preferably 40 wt% or less. This reduces the amount of components removed during firing, thereby suppressing porosity in the internal electrode layer after firing.

[0032] 6. Other additives The conductive paste may contain various additives, provided that they do not significantly impair the effects of the technology disclosed herein. Examples of such additives include dispersants, thickeners, sintering aids, plasticizers, pH adjusters, stabilizers, leveling agents, defoamers, antioxidants, preservatives, and colorants (pigments, dyes).

[0033] For example, dispersants adsorb onto the surface of inorganic particles (conductive particles, co-material particles) and stabilize the solid-liquid interface between the inorganic particles and the organic solvent. This inhibits contact between inorganic particles and prevents the formation of coarse particles due to aggregation. As a result, it can contribute to improved workability during film formation and thinning of the internal electrode layer. Examples of dispersants include anionic dispersants such as carboxylic acid-based dispersants, phosphoric acid-based dispersants, and sulfonic acid-based dispersants. The amount of dispersant added when the total mass of the conductive paste is 100 wt% is preferably 0.1 wt% or more, more preferably 0.25 wt% or more, even more preferably 0.5 wt% or more, and particularly preferably 0.75 wt% or more. This allows for more effective prevention of aggregation of inorganic particles. On the other hand, the upper limit of the amount of dispersant added is preferably 1.5 wt% or less, more preferably 1.25 wt% or less, and particularly preferably 1 wt% or less. Since dispersants are organic components that are burned away during firing, reducing the amount added can contribute to densifying the internal electrode layer.

[0034] Furthermore, as mentioned above, if the melting and sintering of PZT-Zn particles proceeds excessively during firing, Zn will detach from the PZT-Zn particles, making Zn deposition more likely after firing. Considering this, it is preferable that the conductive paste disclosed herein substantially does not contain sintering aids. This allows for more reliable suppression of Zn deposition. Examples of sintering aids here include metal oxides containing alkali metals and alkaline earth metals (such as Ba).

[0035] In this context, "substantially free of sintering aids" means that no additives have been made for the purpose of promoting Zn deposition by sintering of the co-material particles (PZT-Zn particles). Therefore, if a very small amount of a component that could be interpreted as a sintering aid is present, it is included in the concept of "substantially free of sintering aids" as specified herein. For example, if the content of sintering aids is 0.1 wt% or less (preferably 0.05 wt% or less, more preferably 0.01 wt% or less, even more preferably 0.005 wt% or less, and especially preferably 0.001 wt% or less) when the total mass of the conductive paste is 100 wt%, it can be said that it "substantially free of sintering aids."

[0036] The conductive paste disclosed herein has been described above. In this conductive paste, a deposition inhibitor containing Ti and / or Zr is attached to the surface of PZT-Zn particles (common material particles). This deposition inhibitor suppresses the desorption of Zn due to excessive sintering of the PZT-Zn particles and also suppresses the deposition of Zn as a single element after desorption. Furthermore, in the conductive paste disclosed herein, since the deposition inhibitor is attached to the surface of the PZT-Zn particles, the deposition inhibitory effect on Zn can be exerted more effectively. In addition, since the deposition inhibitor is the same element (Ti and / or Zr) as the B site of the PZT-Zn particles, it can prevent a decrease in piezoelectric properties due to the inclusion of impurity elements. Therefore, the conductive paste disclosed herein can suppress Zn deposition after firing while suppressing the drawback of a decrease in piezoelectric properties.

[0037] [Preparation of conductive paste] The means for preparing the conductive paste disclosed herein are not particularly limited, and conventionally known means can be used as appropriate. For example, the conductive paste can be prepared by weighing conductive particles, co-material particles, precipitation inhibitor, binder, organic solvent, and other additives in predetermined proportions (mass ratios) and stirring and mixing them homogenously. Conventionally known mixing and stirring devices can be used without particular limitation for paste preparation. Examples of such stirring and dispersion devices include ball mills, bead mills, roll mills, magnetic stirrers, planetary mixers, dispersers, high-pressure dispersers, mortars, and the like.

[0038] As stated above, the method for attaching the precipitation inhibitor to the surface of the co-material particles is not particularly limited, and conventionally known methods can be appropriately selected according to the form of the precipitation inhibitor. For example, when using particulate precipitation inhibitor, the following procedure can be adopted. First, a vehicle is prepared by mixing organic components such as organic solvents and binders. The co-material particles and the precipitation inhibitor are added to this vehicle and mixed and stirred. This causes the precipitation inhibitor to adhere to the surface of the co-material particles. Then, by adding conductive particles to this vehicle, the conductive paste disclosed herein can be prepared. Furthermore, when using metal organic compounds containing Ti or Zr as precipitation inhibitors, it is preferable to pre-mix the co-material particles and the precipitation inhibitor. This allows the surface of the co-material particles to be coated with the precipitation inhibitor. However, the technology disclosed herein is not limited to the form in which the co-material particles and the precipitation inhibitor are pre-mixed. For example, if a composite material (such as core-shell particles) is pre-formed with a deposition inhibitor attached to the surface of the co-material particles, the conductive particles, co-material particles, and deposition inhibitor can be mixed simultaneously.

[0039] [Uses of conductive paste] As described above, the conductive paste disclosed herein is used in the manufacture of multilayer piezoelectric components. In the manufacture of these multilayer piezoelectric components, first, a piezoelectric sheet containing piezoelectric material is arranged. Next, a conductive paste is applied to the surface of this piezoelectric sheet. The means for applying the conductive paste can be any conventionally known method without particular limitation. Examples of application methods include printing methods such as screen printing, gravure printing, offset printing, and inkjet printing, as well as spray coating and dip coating methods. Then, in the manufacture of the multilayer piezoelectric component, a laminate is created by repeatedly arranging piezoelectric sheets and applying conductive paste. By drying and firing this laminate, a multilayer piezoelectric component is manufactured in which multiple piezoelectric layers and internal electrode layers are alternately laminated.

[0040] The conductive paste disclosed herein uses PZT-Zn particles as co-material particles, enabling the suitable manufacture of multilayer piezoelectric components even at low temperatures of 1100°C or below. Furthermore, because a deposition inhibitor (Ti or Zr) is attached to the surface of the PZT-Zn particles, the deposition of Zn in the internal electrode layer after firing can be suppressed. In other words, the conductive paste disclosed herein enables the manufacture of high-quality multilayer piezoelectric components at low temperatures.

[0041] [Example Test] The following describes test examples relating to the technology disclosed herein. However, the following description is not intended to limit the technology disclosed herein to those shown in the test examples.

[0042] <First Exam> In this study, we conducted experiments to investigate elements that can suppress Zn deposition after firing in conductive paste containing PZT-Zn particles. To emphasize the effectiveness of the technology disclosed herein, the experiments were also conducted using a co-material paste without conductive particles.

[0043] 1. Preparation of the joint material paste (1) Sample 1 In Sample 1, a co-material paste was prepared by mixing co-material particles, a binder, a dispersant, and an organic solvent. PZT-Zn particles with an average particle size of 0.05 μm were used as the co-material particles. Ethyl cellulose was used as the binder. A carboxylic acid-based dispersant was used as the dispersant. Dihydroterpineol was used as the organic solvent. In preparing the co-material paste, the organic components of the organic solvent, binder, and dispersant were pre-mixed to prepare a vehicle, after which the co-material particles were added and stirred. The content of each component is shown in Table 1 below. Note that the content in Table 1 represents the amount added when the co-material particles are considered as 100%.

[0044] (2) Sample 2 In Sample 2, the co-material paste was prepared under the same conditions as in Sample 1, except that a Ti resinate (titanium resin salt) was attached to the surface of the co-material particles. Specifically, in the preparation of Sample 2, the surface of the co-material particles was coated with Ti resinate by adding and mixing the co-material particles and Ti resinate in a vehicle. Note that the amount of attached material in Table 1 is expressed as the ratio X / Y of the number of moles of the precipitation-inhibiting element (Ti in Sample 2) to the number of moles of Zn Y in the co-material particles (PZT-Zn particles).

[0045] (3) Sample 3 In Sample 3, the co-material paste was prepared under the same conditions as in Sample 2, except that the Ti resinate was replaced with Ba resinate (barium resin salt).

[0046] (4) Sample 4 In Sample 4, the co-material paste was prepared under the same conditions as in Sample 2, except that the Ti resinate was replaced with Zr resinate (zirconium resin salt).

[0047] 2. Evaluation Test (1) Preparation of evaluation samples In this test, the test material paste was first applied to the surface of a PET film to a thickness of 250 μm. Next, it was dried at 100°C for approximately 30 minutes, then crushed and pressed to form pellets. These pressed pellets were then fired at 1050°C for 1 hour to produce fired specimens for evaluation.

[0048] (2) Sintering progress The fired bodies of each sample were observed using a scanning electron microscope (SEM) (magnification: 5000x). SEM images of samples 1-4 are shown in Figures 1-4. In this study, the degree of sintering progress was evaluated based on the SEM images of each sample. The evaluation of the degree of sintering progress was carried out according to the following criteria. The evaluation results are shown in Table 1. ○: The structure of inorganic particles after firing is uniform. △: Precipitation and growth of inorganic particles are observed after firing. ×: The sintering of inorganic particles has progressed to a state of oversintering.

[0049] (2) Zn precipitation state Needle-shaped Zn particles were observed in the calcined films where Zn deposition occurred. In this evaluation, the average number of deposited Zn particles across three fields of view was measured and evaluated according to the following criteria. The evaluation results are shown in Table 1. ◎: No precipitation of Zn particles was observed. ○: The average number of precipitated Zn particles is lower than "△", and the size is also smaller. △: The number of precipitated Zn particles is less than that of "×", but the size is the same. ×: More than 40 Zn particles are observed in a field of view of 11 μm × 15 μm. -: A large amount of Zn particles and other inorganic particles sintered together, making it impossible to measure the average number of precipitates.

[0050] [Table 1]

[0051] As shown in Table 1 and Figures 1-4, the precipitation growth of Zn particles was prevented in samples 2 and 4. This indicates that Ti and Zr function as precipitation inhibitors that suppress Zn precipitation from PZT-Zn particles. On the other hand, in sample 3, the precipitation of Zn particles was greatly promoted. In addition, very coarse Zn particles were observed in sample 3. This indicates that coating the surface of the co-material particles with a sintering aid such as Ba promotes the precipitation of Zn particles.

[0052] <Second Exam> In the second test, the relationship between the amount of precipitation inhibitor added and its precipitation inhibitory effect on Zn was investigated. Specifically, for samples 5 to 7, the co-material paste was prepared using the same procedure as for sample 2 in the first test, except that the amount of precipitation inhibitor (Ti resinate) added was different. The amount of precipitation inhibitor added (amount of Ti) for each sample is shown in Table 2.

[0053] In the second test, fired bodies were prepared using the same procedure as in the first test, and observed using a scanning electron microscope (SEM). SEM images of samples 5-7 are shown in Figures 5-7. The degree of sintering and the state of Zn deposition were also evaluated using the same procedure as in the first test. The evaluation results are shown in Table 2.

[0054] [Table 2]

[0055] As shown in Table 2, it was confirmed that the precipitation inhibition effect on Zn improved as the amount of Ti increased. In particular, the conductive paste used in this test contained 0.01 mol of Zn in the PZT-Zn particles. Considering this, it can be concluded that the precipitation inhibition effect on Zn is significantly improved when the number of moles of Ti in the precipitation inhibitor is greater than or equal to the number of moles of Zn in the co-material particles.

[0056] <The Third Test> In the third test, a co-material paste using a particulate precipitation inhibitor was evaluated. Specifically, in Sample 8, a co-material paste with the same composition as Sample 7 (Ti content: 0.02 mol) was prepared, except that TiO2 particles (average particle size: 15 nm) were used as the precipitation inhibitor instead of Ti resinate. In the preparation of Sample 8, the co-material particles and TiO2 particles were added to a vehicle and stirred to adhere the TiO2 particles to the surface of the co-material particles.

[0057] Next, for samples 9 and 10, the co-material paste was prepared using the same procedure as for sample 8, except that the Ti content was changed. Similarly, for sample 11, the co-material paste was prepared using the same procedure as for sample 10, except that the average particle size of the TiO2 particles was changed. The detailed compositions of samples 8 to 11 are shown in Table 3.

[0058] In the third test, the same procedure as in the first test was used to prepare the fired body, and observation was performed using a scanning electron microscope (SEM). SEM images of samples 8-11 are shown in Figures 8-11. The evaluation results for the degree of sintering and the state of Zn deposition are shown in Table 3.

[0059] [Table 3]

[0060] As shown in Table 3 and Figures 8-11, Zn deposition was suppressed in all of samples 8-11. This indicates that deposition inhibitors are not limited to metal-organic compounds (resinates), and particulate deposition inhibitors can also be used. Furthermore, it was found that a higher amount of particulate deposition inhibitor is preferable to that of metal-organic compounds to produce an appropriate deposition inhibitory effect. In addition, comparing sample 10 and sample 11, Zn deposition was more suppressed in sample 10. This indicates that Zn deposition is more easily suppressed as the average particle size of TiO2 particles decreases.

[0061] The technologies disclosed herein have been described in detail above, but these are merely illustrative examples and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. Furthermore, the technologies disclosed herein encompass the forms described in the following sections.

[0062] <Item 1> A conductive paste for a multilayer piezoelectric component comprising conductive particles, co-material particles, a binder, and an organic solvent, The aforementioned co-material particles are perovskite-type oxides containing at least Pb, Zr, Ti, and Zn. A conductive paste characterized in that a deposition inhibitor containing Ti and / or Zr is attached to the surface of the aforementioned co-material particles.

[0063] <Item 2> The conductive paste according to item 1, wherein the precipitation inhibitor is precipitation inhibitor particles attached to the surface of the co-material particles.

[0064] <Item 3> The conductive paste described in item 2, wherein the average particle size of the precipitate-suppressing particles is 300 nm or less.

[0065] <Item 4> The conductive paste according to item 2 or 3, wherein the ratio X / Y of the total number of moles of Ti and Zr in the deposition-suppressing particles to the number of moles of Zn in the co-material particles Y is 0.5 or more and 10 or less.

[0066] <Item 5> The conductive paste according to item 1, wherein the precipitation inhibitor is a precipitation inhibitor film that covers the surface of the co-material particles.

[0067] <Item 6> The conductive paste according to any one of items 1 to 5, wherein the conductive particles comprise at least Ag and Pd.

Claims

1. A conductive paste for a multilayer piezoelectric component comprising conductive particles, co-material particles, a binder, and an organic solvent, The aforementioned co-material particles are perovskite-type oxides containing at least Pb, Zr, Ti, and Zn. A conductive paste characterized in that a deposition inhibitor containing Ti and / or Zr is attached to the surface of the aforementioned co-material particles.

2. The conductive paste according to claim 1, wherein the precipitation inhibitor is precipitation inhibitor particles attached to the surface of the co-material particles.

3. The conductive paste according to claim 2, wherein the average particle size of the precipitate-suppressing particles is 300 nm or less.

4. The conductive paste according to claim 2 or 3, wherein the ratio X / Y of the total number of moles of Ti and Zr in the precipitation-suppressing particles to the number of moles of Zn in the co-material particles Y is 0.5 or more and 10 or less.

5. The conductive paste according to claim 1, wherein the precipitation inhibitor is a precipitation inhibitor film that covers the surface of the co-material particles.

6. The conductive paste according to claim 1, wherein the conductive particles comprise at least Ag and Pd.

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