JP2010225911A - Laminated piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated piezoelectric element that is prevented more securely from decreasing in insulating resistance and is therefore superior in durability. <P>SOLUTION: The laminated piezoelectric element 1 includes a ceramic laminate 15 formed by laminating a piezoelectric ceramic layer 10 and internal electrode layers 13 and 14 alternately, and a pair of side electrodes 17 and 18. The ceramic laminate 15 has a stress relaxation portion 11 which is recessed inward from a side surface 151. When the piezoelectric layer 10 including the stress relaxation portion 11 is defined as a stress relaxation layer 10a, an internal electrode layer electrically connected to a side electrode 17 on a negative electrode side out of two internal electrode layers 13a and 14a adjoining each other across the stress relaxation portion 10a is defined as a reference electrode layer 13a, and the piezoelectric ceramic layer which is not the stress relaxation layer 10a out of the two piezoelectric ceramic layers 10a and 10b adjoining each other across the reference electrode layer is defined as an insulating decrease layer 10b, the stress relaxation layer 10a and/or insulating decrease layer 10b is made principally of a PZT-based material having a larger A-site/B-site ratio than the other piezoelectric ceramic layer 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention has a ceramic laminate formed by alternately laminating a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers, and a pair of side electrodes formed on the side surfaces of the ceramic laminate, The present invention relates to a multilayer piezoelectric element in which a slit-like stress relaxation portion that is recessed inward from a side surface of a body is formed.

Conventionally, a laminated piezoelectric element has been used as a drive source for a fuel injection valve. For example, a multilayer piezoelectric element is formed by bonding a pair of side electrodes that are alternately electrically connected to the internal electrode layer to the side surface of a ceramic laminate in which a plurality of internal electrode layers and piezoelectric ceramic layers are alternately stacked. It becomes.
The laminated piezoelectric element is used over a long period under severe conditions, particularly in applications such as fuel injection valves. Therefore, for example, in order to improve the electrical insulation of the side surface, a ceramic laminated body having an internal electrode non-formation region in which a part of the end portion of the internal electrode recedes inward is widely used.
However, when the internal electrode non-formation region is formed as described above in order to improve the insulation, when a voltage is applied to the ceramic laminate, a deformed portion and a hard-to-deform portion are generated, and the boundary portion is formed. There was a risk of stress concentration and cracking in the device.

In order to avoid the occurrence of cracks due to stress concentration, a multilayer piezoelectric element having grooves (stress relaxation portions) formed at predetermined intervals in the stacking direction on the side surface of the ceramic laminate has been developed (patent) Reference 1).
In addition, in order to avoid the occurrence of cracks, a multilayer piezoelectric element has been developed in which internal electrodes sandwiching a stress relaxation portion have the same polarity (see Patent Document 2).

JP 62-271478 A JP 2006-216850 A

  However, even when the stress relaxation part is formed as in Patent Document 1, when a voltage is applied to the stress relaxation part, there is a possibility that a crack may occur from the tip of the stress relaxation part. In order to avoid this, it is necessary to make the depth of the stress relaxation portion (groove portion) in the direction perpendicular to the stacking direction larger than the receding distance from the side surface of the internal electrode non-formation region. However, with such a configuration, there is a problem that when a large voltage is applied to the stress relaxation portion (groove portion), sufficient insulation cannot be secured, and the life of the multilayer piezoelectric element is shortened.

Further, as in Patent Document 2, when the internal electrodes sandwiching the stress relaxation portion are made the same pole, the piezoelectric layer including the stress relaxation portion becomes a piezoelectric inactive layer. Therefore, when the piezoelectric element expands and contracts, stress can be concentrated on the piezoelectric inactive layer. As a result, even if a crack occurs, it is possible to reliably prevent a crack from selectively (preferentially) entering the stress relaxation part and to generate a crack in the piezoelectric active layer of the laminate, thereby improving durability. It was thought that it could be made.
However, in practice, even if there is no crack in the stress relaxation part, sufficient insulation cannot be obtained, and there is still a problem that the insulation resistance is lowered and a short circuit occurs. . In addition, an electric field is not applied to the ceramic layer including the stress relaxation portion sandwiched between the internal electrode layers having the same polarity, and the ceramic layer is hardly displaced. Therefore, there has been a problem that the amount of displacement of the multilayer piezoelectric element is reduced.

  As described above, in the conventional multilayer piezoelectric element, the piezoelectric ceramic layer including the stress relaxation portion is used as a driving layer in order to improve the amount of displacement, but a sufficient life cannot be ensured.

  The present invention has been made in view of such a conventional problem, and intends to provide a laminated piezoelectric element excellent in durability by preventing a decrease in insulation resistance more reliably without impairing displacement performance. Is.

According to a first aspect of the present invention, there is provided a ceramic laminate formed by alternately laminating a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers mainly composed of a PZT material represented by a basic composition formula ABO ₃ , and the ceramic laminate In a laminated piezoelectric element having a pair of side electrodes formed on side surfaces in a direction perpendicular to the laminating direction of the body,
The internal electrode layer includes a conductive internal electrode portion, and an internal electrode non-formation region in which an outer peripheral end portion of the internal electrode portion recedes inward from the outer peripheral surface of the ceramic laminate by a predetermined receding distance. And alternately electrically connected to any one of the side electrodes in the internal electrode portion,
The ceramic laminate has a slit-like stress relaxation portion that is recessed inward from the side surface of the ceramic laminate at a predetermined depth,
The piezoelectric ceramic layer including the stress relaxation portion is used as a stress relaxation layer, and is electrically connected to the side electrode on the negative electrode side of two internal electrode layers adjacent to each other with the stress relaxation layer sandwiched in the stacking direction of the ceramic laminate. When the internal electrode layer connected to the reference electrode layer is used as a reference electrode layer, and the two piezoelectric ceramic layers adjacent to each other with the reference electrode layer sandwiched between them are non-stress relaxation layers, the stress reduction layer And / or the insulation lowering layer is a laminated piezoelectric element characterized in that a PZT-based material having a larger A-site / B-site ratio than the other piezoelectric ceramic layers is a main component. .

According to a second aspect of the present invention, there is provided a ceramic laminate formed by alternately laminating a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers mainly composed of a PZT-based material represented by the basic composition formula ABO ₃ , and the ceramic laminate In a laminated piezoelectric element having a pair of side electrodes formed on side surfaces in a direction perpendicular to the laminating direction of the body,
The internal electrode layer includes a conductive internal electrode portion, and an internal electrode non-formation region in which an outer peripheral end portion of the internal electrode portion recedes inward from the outer peripheral surface of the ceramic laminate by a predetermined receding distance. And alternately electrically connected to any one of the side electrodes in the internal electrode portion,
The ceramic laminate has a slit-like stress relaxation portion that is recessed inward from the side surface of the ceramic laminate at a predetermined depth,
The stress relaxation part is a multilayer piezoelectric element obtained by firing a relaxation part forming material containing a disappearing material and a Pb oxide that disappear during firing.

Next, the effect of the present invention will be described.
The inventors of the present application have conducted intensive research on problems in forming a stress relaxation portion such as a groove of a multilayer piezoelectric element, and as a result, a piezoelectric ceramic layer (stress relaxation layer) including a stress relaxation portion in the stacking direction of the multilayer piezoelectric element. A negative electrode layer (an internal electrode layer electrically connected to the negative electrode side electrode) and a positive electrode layer adjacent to the negative electrode layer (an internal electrode layer electrically connected to the positive electrode side electrode) It has been found that the insulation resistance of the sandwiched piezoelectric ceramic layer (the insulation lowering layer) is the earliest.
Regarding this detail, first, a decrease in insulation resistance of a general multilayer piezoelectric element will be described.

  In general, when a high electric field is continuously applied to a multilayer piezoelectric element at a high temperature, a phenomenon in which a low resistance region spreads from the negative electrode layer (internal electrode portion) to the surrounding piezoelectric ceramic layer appears. This is because, for example, when a laminated piezoelectric element is fabricated by integral firing of piezoelectric ceramics and an internal electrode layer, conductive metal ions existing in an ionic state diffused from the internal electrode layer to the piezoelectric ceramic layer at the time of integral firing. This is because the low resistance region is formed by being metallized by electrons emitted from the negative electrode layer during driving, and this low resistance region grows toward the positive electrode side. Due to this phenomenon, the electric field strength between the + electrode layer and the − electrode layer is substantially increased, and the decrease in insulation resistance is accelerated. The spread of the low resistance region is accelerated by the presence of moisture.

Specifically, for example, during integral firing, Ag ⁺ ions diffused from the internal electrode portion made of AgPd electrode or the like to the piezoelectric ceramic layer made of PZT or the like are metallized by electrons emitted from the internal electrode portion on the negative electrode side during driving. As a result, a low resistance region is formed, and the phenomenon that the low resistance region grows toward the positive electrode side occurs (Ag ⁺ + e ⁻ → Ag metal).
In particular, in the case of a multilayer piezoelectric element having a slit-like stress relief portion that is recessed from the side surface, the stress relief portion can be a passage leading to the outside where moisture exists, so that the internal electrode layer on the negative electrode side closest to the stress relief portion ( In the reference electrode layer), the above-described spreading phenomenon of the low resistance region becomes particularly remarkable. Further, when a large voltage is applied to the stress relaxation portion, discharge occurs in the stress relaxation portion, element degradation occurs, and the spread of the low resistance region is accelerated.

Therefore, as shown in FIG. 31, among the plurality of piezoelectric ceramic layers 90 in the multilayer piezoelectric element 9, the piezoelectric ceramic layer including the stress relaxation portion 91 is used as the stress relaxation layer 90a, and the stress relaxation layer 90a is sandwiched in the stacking direction. When the internal electrode layer electrically connected to the negative side electrode 97 is the reference electrode layer 93a, the two piezoelectric ceramic layers adjacent to each other with the reference electrode layer 93a interposed therebetween. Of 90, the insulation resistance of the piezoelectric ceramic layer (insulation lowering layer 90b) which is not the stress relaxation layer 90a is the earliest. In particular, in the piezoelectric layer driving region end portion 99 where both the electric field strength and the stress generated by the inverse piezoelectric effect are concentrated, the insulation resistance is further rapidly reduced. The piezoelectric layer driving region end 99 referred to here corresponds to the outer peripheral end 99 of the internal electrode portion 941 in the reference electrode layer 93a adjacent to the stress relaxation layer 90a in the stacking direction of the multilayer piezoelectric element 9, and the reference electrode layer 93a. A portion 99 where the reference electrode layer 93a intersects with the perpendicular line dropped in the stacking direction from the outer peripheral end portion 949 of the internal electrode portion 941 in the internal electrode layer 94a on the positive electrode side closest to the stacking direction in the stacking direction. is there.
Thus, the inventors of the present application have clarified the mechanism of lowering the insulation resistance in the multilayer piezoelectric element having the stress relaxation portion.

  Paying attention to such an insulation resistance lowering mechanism, the present inventors have found that a decrease in insulation resistance can be suppressed by increasing the A site / B site ratio of the composition of the piezoelectric ceramic layer around the stress relaxation portion. It came.

  That is, in the first invention, the stress relaxation layer and / or the insulation lowering layer is mainly composed of a PZT-based material having a larger A-site / B-site ratio than the other piezoelectric ceramic layers. That is, the A site / B site ratio in the composition of the PZT material of the stress relaxation layer is made larger than the composition of the other piezoelectric ceramic layers excluding the stress relaxation layer. Further, the A site / B site ratio in the composition of the PZT-based material of the insulation lowering layer is made larger than the composition of the other piezoelectric ceramic layers excluding the insulation lowering layer. Further, the A site / B site ratio in the composition of the PZT-based material of the stress relaxation layer and the insulation lowering layer is larger than the composition of the other piezoelectric ceramic layers excluding the stress relaxation layer and the insulation lowering layer. To do.

  In this way, by increasing the A site / B site ratio in the stress relaxation layer and / or the insulation lowering layer, conductive metal such as Ag diffuses from the internal electrode portion of the reference electrode layer. Can be suppressed. Therefore, the formation and growth of the low resistance region due to the diffusion of the conductive metal can be suppressed while the stress relaxation layer including the stress relaxation portion is used as the drive layer. Therefore, it is possible to suppress a decrease in insulation resistance without impairing the amount of displacement and improve the durability of the multilayer piezoelectric element.

  In the second invention, the stress relaxation part is formed by firing the relaxation part forming material containing the disappearing material and the Pb oxide that disappear during firing. Therefore, in the multilayer piezoelectric element of the second invention, the disappearing material in the relaxation portion forming material disappears during firing to form the slit-shaped stress relaxation portion, and the relaxation portion forming material It is considered that Pb diffuses from the Pb oxide therein to the piezoelectric ceramic layer around the stress relaxation portion, and the A site / B site ratio in the composition increases. Therefore, diffusion of conductive metal such as Ag from the internal electrode portion of the reference electrode layer can be suppressed. Therefore, it is possible to suppress a decrease in insulation resistance without impairing the amount of displacement and improve the durability of the multilayer piezoelectric element.

  As described above, according to the present invention, it is possible to provide a multilayered piezoelectric element that can more reliably prevent a decrease in insulation resistance without impairing displacement performance and is excellent in durability.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the whole structure of the laminated piezoelectric element concerning Example 1. FIG. FIG. 3 is an explanatory diagram illustrating a cross-sectional structure of the multilayer piezoelectric element according to the first embodiment. FIG. 3 is an explanatory diagram illustrating a cross-sectional structure around the stress relaxation portion of the multilayer piezoelectric element according to the first embodiment. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the process of forming an electrode material on a 1st green sheet with the pattern which an electrode material exposes to one side surface of a laminated body at the time of lamination | stacking concerning Example 1, and producing a 1st electrode printed sheet. Explanatory drawing which shows the process of forming electrode material on a 1st green sheet with the pattern which electrode material exposes to the other side surface of a laminated body at the time of lamination | stacking concerning Example 1, and producing a 1st electrode printed sheet. . Explanatory drawing which shows the process of forming an electrode material on a 2nd green sheet with the pattern which an electrode material exposes to one side surface of a laminated body at the time of lamination | stacking concerning Example 1, and producing a 2nd electrode printed sheet. Explanatory drawing which shows the process of forming an electrode material on a 2nd green sheet with the pattern which an electrode material exposes to the other side surface of a laminated body at the time of lamination | stacking concerning Example 1, and producing a 2nd electrode printed sheet. . Explanatory drawing which shows the process of producing the mitigation part arrangement | positioning sheet | seat concerning Example 1. FIG. Explanatory drawing which shows the process of laminating | stacking the 1st electrode printing sheet, 2nd electrode printing sheet, and relaxation part arrangement | positioning sheet | seat concerning Example 1. FIG. FIG. 2 is a top view of a pre-laminated body according to Example 1. Sectional drawing of the preliminary | backup laminated body concerning Example 1 (AA arrow directional cross-sectional view of FIG. 10). FIG. 3 is an explanatory view showing a cross-sectional structure of an intermediate laminate according to Example 1. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the structure of the laminated type piezoelectric element concerning Example 1 in which the stress relaxation part exposed to the alternately different side surface was formed in a different layer. FIG. 3 is a development explanatory view of a ceramic laminate showing a formation pattern of internal electrode portions and stress relaxation portions according to Example 1; Explanatory drawing which shows the variation (a)-(c) of the formation pattern of an internal electrode part and a slit layer concerning Example 1 with the expanded view of a ceramic laminated body. FIG. 6 is an explanatory diagram showing the overall structure of a multilayer piezoelectric element according to Example 2. FIG. 6 is an explanatory diagram showing a cross-sectional structure of a multilayer piezoelectric element according to Example 2. FIG. 6 is an explanatory diagram showing a cross-sectional structure around a stress relaxation portion of a multilayer piezoelectric element according to Example 2. Explanatory drawing which shows the process of producing the mitigation part arrangement | positioning sheet | seat concerning Example 2. FIG. Explanatory drawing which shows the process of laminating | stacking the 1st electrode printing sheet, 2nd electrode printing sheet, and relaxation part arrangement | positioning sheet | seat concerning Example 2. FIG. FIG. 6 is a top view of a preliminary laminate according to the second embodiment. Sectional drawing of the preliminary | backup laminated body concerning Example 2 (BB sectional view taken on the line of FIG. 21). FIG. 6 is an explanatory view showing a cross-sectional structure of an intermediate laminate according to Example 2. FIG. 6 is an explanatory diagram showing a cross-sectional structure of a multilayer piezoelectric element according to Example 2 in which stress relaxation portions that are alternately exposed on different side surfaces are formed in substantially the same layer as an internal electrode layer. FIG. 6 is an explanatory diagram showing the overall structure of a multilayer piezoelectric element according to Example 3. FIG. 6 is an explanatory diagram illustrating a cross-sectional structure of a multilayer piezoelectric element according to Example 3. FIG. 6 is an explanatory diagram showing a cross-sectional structure around a stress relaxation portion of a multilayer piezoelectric element according to Example 3. Explanatory drawing which shows the process of producing the mitigation part arrangement | positioning sheet | seat concerning Example 3. FIG. Explanatory drawing which shows the cross-section of the preliminary | backup laminated body formed by laminating | stacking the electrode printing sheet and relaxation part arrangement | positioning sheet | seat concerning Example 3. FIG. Explanatory drawing which shows the cross-section of the intermediate | middle laminated body concerning Example 3. FIG. Explanatory drawing which shows the cross-sectional structure of the stress relaxation part periphery in a laminated piezoelectric element, and shows the edge part of a piezoelectric drive area where both the electric field strength and the stress generated by the inverse piezoelectric effect tend to concentrate. Explanatory drawing which shows the cross-sectional structure of the laminated piezoelectric element by which the slit-shaped groove part other than a stress relaxation part was formed in the side surface.

Next, a preferred embodiment of the present invention will be described.
The multilayer piezoelectric element 1 of the present invention includes the ceramic laminate 15 and a pair of side electrodes 17 and 18 formed on the side surface 151 of the ceramic laminate 15 (see FIGS. 1 to 3). The internal electrode layers 13, 14 have conductive internal electrode portions 131, 141, and the outer peripheral end portions of the internal electrode portions 131, 141 are set back inwardly from the outer peripheral side surface 151 of the ceramic laminate 15. Internal electrode non-formation regions 132 and 142 receding at a distance 135 are included. The outer peripheral side surface 151 is a side surface in the direction perpendicular to the stacking direction in the ceramic laminate 15. The internal electrode non-formation regions 132 and 142 are regions in which internal electrodes that are substantially on the same plane as the internal electrode portions 131 and 141 are not formed (see FIGS. 1 to 3 and 14). The internal electrode non-formation regions 132 and 142 are formed by pressure bonding the piezoelectric ceramic layers 10 sandwiching the internal electrode portions 131 and 141 at the time of fabrication. In practice, the piezoelectric layers are coplanar with the internal electrode portions 131 and 141. It is formed of ceramics.
By providing the internal electrode non-formation regions 132 and 142, the internal electrode layers 13 and 14 can realize reliable insulation on one side surface of the ceramic laminate 15 (the side surface on the internal electrode non-formation region side). . The receding distance 135 is the shortest distance between the end portions of the internal electrode portions 131 and 141 and the side surface 151 of the ceramic laminate 15 across the internal electrode non-formation regions 132 and 142.

  The ceramic laminate is formed by alternately laminating a plurality of the piezoelectric ceramic layers and the internal electrode layers. The ceramic laminate includes the slit-shaped stress relaxation portion that is recessed inward from the side surface of the ceramic laminate by a predetermined depth. Specifically, the stress relaxation part is a slit-like groove part or the like.

In the present invention, the stress relaxation portion 11 is larger than the receding distance 135 of the internal electrode non-formation regions 132 and 142 in the internal electrode layers 13 and 14 in the cross section in the stacking direction of the multilayer piezoelectric element 1. The slit-shaped groove part etc. which were formed by the depth are shown (refer FIG. 32). The slit-like groove may vary in depth, but the groove having at least a portion formed at a depth larger than the receding distance 135 of the internal electrode non-formation regions 132 and 142 has stress relaxation. Part.
Therefore, the slit-like groove portion 199 formed at a depth smaller than the receding distance 135 does not correspond to the stress relaxation portion 11 in the present invention.
More specifically, among the slit-shaped grooves 11 and 199 recessed inward from the side surface of the multilayer piezoelectric element 1, two internal electrode layers 13 adjacent to the piezoelectric ceramic layer 10 including at least the grooves 11 and 199, 14 is a stress relaxation portion 11 formed at a depth larger than the receding distance 135 of the internal electrode non-formation regions 132 and 142 in FIG. It does not correspond to the stress relaxation part 11 in the invention.

The stress relaxation portion is a portion in the ceramic laminate that can change its shape more easily than the piezoelectric ceramic layer because the crystal particles constituting the piezoelectric ceramic are separated in the stacking direction.
A plurality of the stress relaxation portions can be provided at arbitrary intervals in the stacking direction of the ceramic laminate, and the stress accumulated in the stacking direction of the ceramic laminate can be relaxed. When the number of layers is small, the absolute value of the accumulated stress generated when a voltage is applied is small, and cracks are hardly generated in the first place. As a result, there is a possibility that the necessity itself of forming the slit-shaped stress relaxation portion in the ceramic laminate may be almost eliminated. Furthermore, a decrease in electrode area due to the retreat of the internal electrode portion may cause a decrease in displacement performance. Therefore, the ceramic laminate preferably has 10 or more internal electrode layers. For the same reason, the interval in the stacking direction for forming the stress relaxation part is preferably 10 or more internal electrode layers. When the stress relaxation portions are formed with an interval of less than 10 internal electrode layers, a decrease in electrode area due to retreat of the internal electrode portion may cause a decrease in displacement performance. Moreover, it is preferable that the space | interval of the lamination direction which forms the said stress relaxation part is 50 or less internal electrode layers. When formed at intervals exceeding 50 layers, the stress relaxation effect by the stress relaxation portion may not be sufficiently obtained.

Further, the ceramic laminate, when the ceramic laminate is seen through in the laminating direction, superposes only the superposed portion that is a region where all the internal electrode portions are polymerized, and at least a part of the internal electrode portions, or It is preferable that the stress relaxation portion is formed at least in the non-polymerized portion.
In this case, the stress relaxation effect by the stress relaxation part can be exhibited remarkably.
That is, the non-overlapping portion is a portion where piezoelectric displacement does not occur and is not driven. For this reason, stress (strain) is likely to occur intensively in the non-overlapped portion according to the piezoelectric displacement. As described above, the stress applied to the non-polymerized portion can be relaxed by forming the stress relaxation portion in the non-polymerized portion.

The stress relaxation part can be formed by firing a disappearing material that disappears during firing.
As the disappearing material, for example, powdered carbon particles, resin particles, or carbonized organic particles obtained by carbonizing powdered organic particles can be used.
In particular, when the carbon particles are used as the disappearing material, the stress relaxation portion can be formed with high shape accuracy by taking advantage of the characteristics of the carbon particles that the shape change due to heat is small.
Moreover, when the said carbonized organic matter particle | grains are used as the said loss | disappearance material, the cost for forming the said stress relaxation part can be suppressed.
Examples of the organic particles include particles obtained by pulverizing soybeans and corn, and particles obtained by pulverizing a resin material. The carbonized organic particles refer to particles that have been carbonized to some extent by removing a part of the water contained in the organic particles to form fine particles with good fluidity and dispersibility.

  Further, the stress relaxation portion is formed by forming the slit-shaped region with a material that cracks when the stacked piezoelectric element is polarized or driven, and causing cracks when the stacked piezoelectric element is polarized or driven. You can also.

In the multilayer piezoelectric element, the stress relaxation portion can be formed, for example, in the piezoelectric ceramic layer between the internal electrode layers.
Further, the stress relaxation portion can be formed in substantially the same layer as the internal electrode layer (so as to be in contact with the internal electrode layer).

In the multilayer piezoelectric element, the piezoelectric ceramic layer contains a PZT material represented by a basic composition formula ABO ₃ as a main component. In the first invention, the stress relaxation layer and / or the insulation lowering layer is mainly composed of a PZT-based material having a larger A site / B site ratio than the other piezoelectric ceramic layers.
The stress relaxation layer and the insulation lowering layer will be described using a cross-sectional view of a multilayer piezoelectric element (see FIG. 2). FIG. 2 is a cross-sectional view of a multilayer piezoelectric element in which a pair of side surface electrodes 17 and 18 sandwiching the side surface of the ceramic laminate 15 together with the ceramic laminate 15 are cut in the lamination direction.

As shown in the figure, the ceramic laminate 15 has a slit-like stress relaxation portion 11 that is recessed inward from the side surface at a predetermined depth.
Here, the stress relaxation layer 10 a is a piezoelectric ceramic layer including the stress relaxation portion 11 among the plurality of piezoelectric ceramic layers 10 sandwiched between the internal electrode layers 13 and 14.
The internal electrode electrically connected to the side electrode 17 on the negative electrode side of the two internal electrode layers 13a and 14a adjacent to each other across the stress relaxation layer 10a in the stacking direction of the ceramic laminate 15 When the layer is the reference electrode layer 13a, the insulation lowering layer 10b is a piezoelectric ceramic layer that is not the stress relaxation layer 10a among the two piezoelectric ceramic layers 10 adjacent to each other with the reference electrode layer 13a interposed therebetween. .

  When the A site / B site ratio of the PZT material constituting the stress relaxation layer and / or the insulation lowering layer is equal to or lower than the A site / B site ratio in the other piezoelectric ceramic layers, the reference electrode A conductive metal such as Ag is likely to diffuse from the internal electrode portion of the layer, and the insulation resistance may be lowered early.

Further, in all the piezoelectric ceramic layers in the multilayer piezoelectric element, it is preferable that the A-site / B-site ratio of the PZT material constituting the piezoelectric ceramic layer is 1.005 or less ( Claim 2). That is, it is preferable that the A site / B site ratio is 1.005 or less in the entire multilayer piezoelectric element.
When the A site / B site ratio is larger than 1.005, elements constituting the A site such as Pb may be precipitated at the grain boundaries, and the displacement performance of the multilayer piezoelectric element may be impaired. In addition, from the viewpoint that it can be surely sintered at the time of firing in the production of the multilayer piezoelectric element, the A site / B site ratio is preferably 1 or more.

The stress relaxation layer and / or the insulation lowering layer preferably has an A site / B site ratio of at least 0.001 or more as compared with the other piezoelectric ceramic layers.
In this case, the diffusion of conductive metal such as Ag from the internal electrode portion of the reference electrode layer can be more significantly suppressed.

The receding distance of the internal electrode non-formation region in the reference electrode layer is smaller than the depth of the stress relaxation portion existing closest to the reference electrode layer in the stacking direction of the stacked piezoelectric element. Preferred (claim 4). More preferably, the receding distance of the internal electrode non-formation region in all the internal electrode layers is preferably smaller than the depth of the stress relaxation portion existing closest to each internal electrode layer. .
In this case, the area of the internal electrode portion is increased, and the displacement amount of the multilayer piezoelectric element can be improved.

Next, in the second invention, the stress relaxation part is formed by baking a relaxation part forming material containing a disappearing material and a Pb oxide that disappear during baking.
As the disappearing material, for example, powdered carbon particles, resin particles, or carbonized organic particles obtained by carbonizing powdered organic particles can be used as described above.
As the Pb oxide, for example, PbO or a complex oxide containing Pb can be used. Specifically, for example, Pb ₃ O ₄ , PT (lead titanate), PZ (lead zirconate), PZT (lead zirconate titanate), or the like can be used.

The relaxation part forming material preferably contains PbO as the Pb oxide.
In this case, it can be prevented that PbO becomes a volatile component and solid foreign matters are formed in the stress relaxation portion.

The relaxation part forming material preferably contains 20 parts by mass or less of Pb oxide in terms of PbO with respect to 100 parts by mass of the disappearing material.
When the Pb oxide exceeds 20 parts by mass in terms of PbO, Pb may be precipitated at the grain boundary around the stress relaxation part, thereby impairing the displacement performance of the multilayer piezoelectric element. More preferably, it is 15 parts by mass or less, and more preferably 10 parts by mass or less. In addition, the amount of Pb oxide added is preferably 1 part by mass or more from the viewpoint of more reliably obtaining the above-described diffusion suppression effect of the conductive metal by the addition of Pb.

The ceramic laminate includes a ceramic raw material, and a sheet forming step for forming a green sheet that becomes the piezoelectric ceramic layer after firing, and an electrode material on a portion for forming the internal electrode portion on the green sheet. An electrode material disposing step of disposing an electrode disposing sheet and disposing the relaxing portion forming material on a portion of the green sheet where the stress relieving portion is to be formed. A step of disposing the relaxing portion forming material, laminating a plurality of the electrode disposition sheets, laminating the electrode disposition sheets between the electrode disposition sheets at an arbitrary interval in the laminating direction, It can be obtained by performing a laminating step for producing and a firing step for producing the ceramic laminated body by firing the intermediate laminated body.
In this case, after the firing step, the piezoelectric ceramic layer is formed from a green sheet, and the internal electrode portion is formed in a region where the electrode material is disposed. Further, the stress relaxation part is formed in the region where the relaxation part forming material is disposed, and Pb contained in the relaxation part forming material can be diffused around the stress relaxation part.
In addition, the laminated piezoelectric element can be obtained by baking the conductive metal made of Ag or the like on the side surface of the ceramic laminate after the firing step to form the side electrode.

Further, the piezoelectric ceramic layer including the stress relaxation portion is used as a stress relaxation layer, and the side electrode on the negative electrode side of the two internal electrode layers adjacent to each other with the stress relaxation layer sandwiched in the stacking direction of the ceramic laminate. When the electrically connected internal electrode layer is a reference electrode layer, the receding distance of the internal electrode non-formation region in the reference electrode layer is closest to the reference electrode layer in the stacking direction of the stacked piezoelectric element. It is preferable that the depth is smaller than the depth of the stress relaxation portion existing in (Claim 9). More preferably, the receding distance of the internal electrode non-formation region in all the internal electrode layers is preferably smaller than the depth of the stress relaxation portion existing closest to each internal electrode layer.
In this case, the area of the internal electrode portion is increased, and the displacement amount of the multilayer piezoelectric element can be improved.

In the present invention, the internal electrode portion preferably contains an AgPd alloy as a main component (claim 10).
In this case, the internal electrode portion can exhibit excellent conductivity, and the multilayer piezoelectric element having a high displacement can be configured.
Further, in this case, Ag diffusion tends to occur, so that the operational effects of the present invention can be exhibited more remarkably. That is, when forming an internal electrode portion mainly composed of an AgPd alloy, Ag is likely to diffuse during firing. Therefore, as in the first invention and the second invention, the effect of suppressing the insulation resistance reduction by increasing the A site / B site ratio around the stress relaxation portion can be exhibited more remarkably. it can.

  The laminated piezoelectric element is preferably used for a fuel injection valve. In this case, even in severe conditions, the effect of the multilayer piezoelectric element of the present invention that can be stably operated without lowering the insulation resistance over a long period of time can be exhibited more remarkably. .

Example 1
Next, a laminated piezoelectric element according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 to 3, the multilayer piezoelectric element 1 of the present example includes a ceramic laminate 15 in which a plurality of piezoelectric ceramic layers 10 and a plurality of internal electrode layers 13 and 14 are alternately laminated, and a laminate thereof. A pair of side surface electrodes 17 and 18 formed on a side surface 151 in a direction perpendicular to the direction.
The piezoelectric ceramic layer 10 is mainly composed of a PZT material represented by the basic composition formula ABO ₃ .
The internal electrode layers 13 and 14 include internal electrode portions 131 and 141 having conductivity, and internal electrodes whose outer peripheral end portions recede inward from the outer peripheral side surface 151 of the ceramic laminate 15 by a predetermined receding distance 135. The internal electrode layers 13 and 14 are electrically connected to alternately different side electrodes 17 and 18 (see FIGS. 1 to 3 and 14).

  As shown in FIGS. 1 to 3, each internal electrode layer 13, 14 has no boundary with the upper and lower piezoelectric ceramic layers 10 sandwiching the internal electrode layers 13, 14 in the internal electrode non-formation regions 132, 142. Yes. Therefore, the piezoelectric ceramic layer 10 and the internal electrode layers 13 and 14 are not laminated with a complete layered structure. However, in this specification, for the sake of convenience, in the ceramic laminate 15, the internal electrode portions 131, 141 of the internal electrode layers 13, 14 are arranged in a plane extending in the horizontal direction (direction perpendicular to the stacking direction). The formation regions 132 and 142 exist, and the internal electrode layers 13 and 14 including the internal electrode portions 131 and 141 and the internal electrode non-formation regions 132 and 142 are treated as forming a laminated structure with the piezoelectric ceramic layer 10. Accordingly, each piezoelectric ceramic layer 10 is a region sandwiched between two adjacent internal electrode layers 13 and 14.

The ceramic laminate 15 has a stress relaxation portion 11 whose shape can be changed more easily than the piezoelectric ceramic layer 10 in a slit-like region recessed inward from the side surface.
In this example, the stress relaxation part 11 is a slit-like groove (space) recessed inward from the side surface of the ceramic laminate 15, and is formed in the circumferential direction over the entire circumference of the outer peripheral side surface 151 of the ceramic laminate 15. Has been. Further, in this example, the stress relaxation portion 11 is formed in the piezoelectric ceramic layer 10 between the internal electrode layers 13 and 14 and is formed at a position not in contact with the internal electrode layers 13 and 14.

  As shown in FIG. 3, in the cross section in the stacking direction of the multilayer piezoelectric element 1, the depth 115 of the stress relaxation portion 11 exposed at the side surface 151 of the ceramic laminate 15 is formed on the same side surface 151 as the stress relaxation portion 11. The inner electrode non-forming region 142 (132) is larger than the receding distance 135.

  As shown in FIGS. 1 to 3, among the piezoelectric ceramic layers 10, a piezoelectric ceramic layer including the stress relaxation portion 11 is used as a stress relaxation layer 10 a, and is adjacent to each other with the stress relaxation layer 10 a interposed in the stacking direction of the ceramic laminate 15. Of the two internal electrode layers 13a and 14a, the internal electrode layer electrically connected to the side electrode 17 on the negative electrode side is defined as a reference electrode layer 13a, and two adjacent piezoelectric ceramic layers 10a with the reference electrode layer 13a interposed therebetween, 10b, if the piezoelectric ceramic layer that is not the stress relaxation layer 10a is the insulation lowering layer 10b, the insulation lowering layer 10b is a PZT system having a larger A-site / B-site ratio than the other piezoelectric ceramic layers 10 and 10a. The material is the main component.

Next, a method for manufacturing the multilayer piezoelectric element of this example will be described with reference to FIGS.
In this example, by performing the first sheet forming step, the second sheet forming step, the electrode material disposing step, the relaxing portion forming material disposing step, the laminating step, the firing step, and the side surface electrode forming step, An element is manufactured.

In the first sheet forming step, a first green sheet 101 that contains a ceramic raw material and becomes a piezoelectric ceramic layer containing a PZT-based material represented by the basic composition formula ABO ₃ as a main component after firing is formed (FIG. 4 and FIG. 4). (See FIG. 5). Specifically, the first green sheet 101 is formed by forming a slurry-like or paste-like first ceramic raw material for producing a PZT-based material represented by the basic composition formula ABO ₃ after firing into a sheet shape.
Also in the second sheet forming step, a second green sheet 102 is formed which becomes a piezoelectric ceramic layer containing a ceramic raw material and containing the PZT material represented by the basic composition formula ABO ₃ as a main component after firing (FIG. 6). And FIG. 7). In the second sheet forming step, the composition of the second ceramic raw material is prepared so that the A-site / B-site ratio of the PZT-based material after firing is larger than that of the first green sheet. The second green sheet 102 is formed by forming into a sheet shape.

In the electrode material arranging step, as shown in FIGS. 4 to 7, the electrode materials 130 and 140 are arranged on the portion to be the internal electrode portion in the printing region 103 on the first green sheet 101 and the second green sheet 102. The electrode placement sheets 105 and 106 are prepared. As a result, as shown in FIGS. 4 and 5, the first electrode placement sheet 105 in which the electrode materials 130 and 140 are placed on the first green sheet 101, and the second green as shown in FIGS. 6 and 7. A second electrode-disposed sheet 106 in which electrode materials 130 and 140 are disposed on the sheet 102 is obtained.
In the relaxation portion forming material disposing step, as shown in FIG. 8, a relaxation portion forming material containing a disappearing material that disappears during firing in a portion where the stress relaxation portion is formed in the printing region 103 on the first green sheet 101. 110 is provided to prepare the relaxing portion arrangement sheet 107.

  In the laminating step, as shown in FIG. 9, a plurality of electrode arrangement sheets 105 and 106 are laminated, and a relaxation portion arrangement sheet 107 is laminated between the electrode arrangement sheets at an arbitrary interval in the lamination direction. The laminated body 10 is produced. At this time, as the electrode-arranged sheet, the second electrode-arranged sheet 106 is disposed at a position that becomes the insulation lowering layer after firing, and the first electrode-arranged sheet 106 is disposed at other positions.

In the firing step, the intermediate laminate 10 is fired to produce the ceramic laminate 15 (see FIGS. 1 to 3).
In the side electrode forming step, the side electrodes 17 and 18 are formed by baking a conductive metal on the side surface of the ceramic laminate 15 (see FIGS. 1 to 3).

In this example, as shown in FIGS. 4 to 8, a plurality of electrode materials are formed on the green sheet 101 (102) in order to obtain a plurality of ceramic laminates by stacking one wide green sheet 101 (102). As shown in FIG. 12, the intermediate layer 130 and 140 and the relaxation portion forming material 110 are disposed, and as shown in FIG. 9, a laminate cutting process for cutting the laminate 100 (preliminary laminate) after lamination is performed. A body 10 is obtained.
Hereafter, the manufacturing method of this example is demonstrated in detail for every process.

<First sheet forming step and second sheet forming step>
First, a ceramic raw material powder such as lead zirconate titanate (PZT) serving as a piezoelectric material was prepared. Specifically, Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ , and Nb ₂ O ₅ are prepared as starting materials, and these starting materials are used as the target composition PbZrO ₃ —PbTiO ₃ —Pb (Y _{1 / 2} Nb _1/2 ) O ₃ such that the A site / B site ratio (molar ratio), that is, Pb / (Zr + Ti + Y + Nb) is 1.002, 1.003, 1.005, 1.01 respectively. Weighed in a ratio, wet mixed, and calcined at a temperature of 850 ° C. for 5 hours. Next, the calcined powder was wet pulverized by a pearl mill. This calcined powder pulverized product (particle size (D50 value): 0.7 ± 0.05 μm) is dried and then mixed with a ball mill after adding a solvent, a binder, a plasticizer, a dispersant, etc., and the resulting slurry is obtained. While the ceramic raw material was stirred with a stirrer in a vacuum apparatus, vacuum defoaming and viscosity adjustment were performed.
In this example, as described above, a PZT-based material having a target composition containing Pb as the A-site element is used. For example, in addition to Pb, a plurality of elements such as Sr and Ba are included as the A-site element. It is also possible to adopt a PZT-based material. In this case, the A site / B site ratio (molar ratio) can be calculated based on the formula (other elements such as Pb + Sr, Ba) / (Zr + Ti + Y + Nb).

Next, a slurry-like ceramic raw material is applied onto a carrier film by a doctor blade method, and as shown in FIGS. 4 to 7, a long green sheet (a first green sheet 101 and a second green sheet having a thickness of 80 μm). 102). In this example, two types of green sheets 101 and 102 were prepared using two types of ceramic raw materials having different A site / B site ratios. Among these green sheets, the one with the larger A site / B site ratio is the second green sheet 102, and the one with the smaller A site / B site ratio is the first green sheet 101. These green sheets were cut into a predetermined size to produce wide first green sheets 101 and second green sheets 102 (see FIGS. 4 to 7).
In addition to the doctor blade method used in this example, an extrusion molding method and various other methods can be employed as the green sheet molding method.

<Electrode material placement process>
Next, as shown in FIGS. 4 and 5, the electrode materials 130 and 140 were printed in predetermined regions on the first green sheet 101 where the internal electrode portions were to be formed, thereby producing the first electrode-disposed sheet 105. The electrode material was printed with two different types of patterns 130 and 140 on the first green sheet 110 so that the end portions of the electrode material were exposed on different side surfaces of the laminated body during lamination and cutting described later. Similarly, the electrode materials 130 and 140 were printed on the second green sheet 102 to produce the second electrode-arranged sheet 106 (see FIGS. 6 and 7).
In this example, paste-like Ag / Pd alloys were used as the electrode materials 130 and 140. In addition to the above, simple substances such as Ag, Pd, Cu, and Ni, and alloys such as Cu / Ni can be used.

<Relaxation part forming material arrangement process>
Moreover, in this example, since the stress relaxation part 11 (refer FIGS. 1-3) is provided in the side surface of the ceramic laminated body 15 of the multilayer piezoelectric element 1 to be manufactured, as shown in FIG. The relaxation part forming material arrangement | positioning process which produces 107 was performed.
As shown in the figure, on the first green sheet 101, a relaxation portion forming material 110 containing a disappearing material that disappears by firing was printed in a predetermined region that finally becomes a stress relaxation portion. Thereby, the relaxation part arrangement | positioning sheet | seat 107 was formed.

  In this example, as the disappearing material, a material made of carbon particles that is small in thermal deformation and can maintain high shape accuracy of the groove formed by the firing process was used. In addition to carbon particles, carbonized powdery carbonized organic particles can also be used. The carbonized organic particles can be obtained by carbonizing powdery organic particles, or by pulverizing the carbonized organic material. Furthermore, as the organic substance, polymer materials such as resins and grains such as corn, soybeans, and wheat flour can be used. In this case, the manufacturing cost can be suppressed. As the relaxation portion forming material 110, a paste-like material obtained by adding an appropriate amount of a binder or the like to the disappearing material was used.

  In the electrode material disposing step and the relaxing portion forming material disposing step described above, in the ceramic laminate 15 obtained after firing as shown in FIGS. 2 and 3, the stress relaxing portion depth 115 from the side surface 151 is The electrode material and the relaxing portion forming material were disposed so as to be larger than the receding distance 135 of the internal electrode non-formation region (see FIGS. 4 to 8). Further, as shown in FIGS. 4 to 8, the electrode materials 130 and 140 and the relaxing portion forming material 110 are printed with a gap 104 so as to avoid a portion to be cut in a subsequent laminated body cutting step. That is, printing is performed by providing a gap 104 between adjacent print regions 103 on the green sheet 101 (102).

<Lamination process>
Next, as shown in FIG. 9, the first electrode arrangement sheet 105 was laminated. At this time, a plurality of the first electrode arrangement sheets 105 were laminated so that the electrode material patterns 130 and 140 were alternated, and the relaxation portion arrangement sheet 107 was inserted and laminated at the position where the stress relaxation portion was to be formed. Specifically, in this example, the relaxing portion arrangement sheet 107 is laminated for every 11 layers of the laminated structure of the first electrode arrangement sheet 105. In addition, a second electrode disposition sheet 106 was laminated instead of the first electrode disposition sheet 105 in the layer located in the above-described insulation lowering layer. In this way, the first electrode arrangement sheet 105 and the second electrode arrangement sheet 106 are laminated so that there are a total of 59 sheets, and the electrode material and the relaxation portion forming material are printed on both ends in the lamination direction. No green sheet 101 (first green sheet) was laminated.
The sheets laminated in this way were heated at a temperature of 100 ° C. and pressed at 50 MPa in the laminating direction to produce a pre-laminated body 100. In FIG. 9, the preliminary laminated body 100 is shown in a form in which the actual number of laminated layers is omitted for convenience of drawing.

<Laminate cutting process>
Next, as shown in FIGS. 10 to 12, the formed preliminary laminated body 100 was cut in the lamination direction along a predetermined cutting position 190 to form the intermediate laminated body 10.
The preliminary laminated body 100 may be cut for each intermediate laminated body 10 or may be cut so as to include a plurality of intermediate laminated bodies 10. In the present example, each of the intermediate laminates 10 was cut and cut so that the electrode materials 130 and 140 and the relaxing portion forming material 110 were exposed on the side surfaces of the intermediate laminate 10.
In FIGS. 11 and 12, for the convenience of drawing, the preliminary laminated body 100 and the intermediate laminated body 10 are shown in a form in which the actual number of laminated layers is omitted.

  Next, the binder resin contained in the green sheet 101 (102) of the intermediate laminate 10 was removed by heating (degreasing). Heating was performed by gradually raising the temperature to 500 ° C. over 80 hours and holding for 5 hours.

<Baking process>
Next, the degreased intermediate laminate 10 was fired. Firing was performed by gradually raising the temperature to 1050 ° C. over 12 hours, holding for 2 hours, and then gradually cooling.
Thus, the ceramic laminated body 15 which has the slit-shaped stress relaxation part 11 formed by disappearing the relaxation part forming material 110 is produced (see FIGS. 1 to 3). As shown in FIGS. 1 to 3, the stress relaxation part 11 is provided with a slit-like space over the entire side surface of the ceramic laminate 15. Further, as shown in the figure, in the produced ceramic laminate 15, the internal electrode portions 131 and 141 formed by the piezoelectric ceramic layer 10 formed by sintering the first green sheet 101 and the electrode materials 130 and 140 are provided. The internal electrode layers 13 and 14 are alternately stacked. The piezoelectric ceramic layer 10 located in the insulation lowering layer 10b is formed by sintering the second green sheet 102.
And after baking, it grind | polished the whole surface and produced the ceramic laminated body 15 of length 6mm * width 6mm * height 4.4mm.

<Side electrode formation process>
Next, Ag electrodes were baked so as to sandwich both side surfaces of the ceramic laminate 15 to form side electrodes 17 and 18. At this time, the internal electrode layers 13 and 14 are electrically connected to the side electrodes 17 and 18 on the side surfaces that are alternately different in the internal electrode portions 131 and 141, respectively.

As described above, the multilayer piezoelectric element 1 was produced as shown in FIGS.
In FIG. 1 and FIG. 2, the laminated piezoelectric element 1 is shown in a form in which the actual number of layers is omitted for the convenience of drawing.

In this example, ten types of laminated piezoelectric elements (samples X1 to X10) having different A-site / B-site ratios between the insulation lowering layer 10b and the other piezoelectric ceramic layers 10 were produced.
That is, the sample X1 is the multilayer piezoelectric element 1 in which the A site / B site ratio of the insulation lowering layer 10b and the other piezoelectric ceramic layers 10 is 1.01.
In Sample X2 and Sample X3, the A site / B site ratio of the insulation lowering layer 10b is 1.005 and 1.002, respectively, and the A site / B site ratio of the other piezoelectric ceramic layers 10 other than the insulation lowering layer 10b is 1. .01 multilayer piezoelectric element 1.

In Samples X4 to X6, the A site / B site ratio of the insulation lowering layer 10b is 1.01, 1.005, and 1.002, respectively, and the A site / B of the other piezoelectric ceramic layers 10 other than the insulation lowering layer 10b. The multilayer piezoelectric element 1 has a B site ratio of 1.005.
In Sample X7 to Sample X10, the A site / B site ratio of the insulation lowering layer 10b is 1.01, 1.005, 1.003, and 1.002, respectively, and the other piezoelectric ceramic layers 10 other than the insulation lowering layer 10b. The multilayer piezoelectric element 1 has an A site / B site ratio of 1.002.
The A site / B site ratio of the insulation lowering layer 10b in each sample (samples X1 to X10) and the A site / B site ratio of the other piezoelectric ceramic layers 10 are shown in Table 1 described later.

Next, the durability of the multilayer piezoelectric element of each sample was examined.
"Durability test"
Under the condition of a temperature of 200 ° C., an electric field of 3.1 kV / mm was applied to the multilayer piezoelectric element of each sample to drive the multilayer piezoelectric element. Next, each sample was connected in series to a resistor R having a known resistance value to construct a circuit. And the voltage (leakage current value) concerning resistance R was read with the digital meter, applying an electric field to each sample. When the calculated insulation resistance of the element (sample) was less than 10 MΩ, it was regarded as the life of the element, and the time (life) at that time was measured. The results are shown in Table 1.

As known from Table 1, piezoelectric ceramic layers other than the insulation lowering layer have the same A site / B site ratio, that is, each group of sample X1 to sample X3, sample X4 to sample X6, and sample X7 to sample X10. When the samples in the sample are compared with each other, samples (sample X4 and samples X7 to X9) in which the A site / B site ratio of the insulation lowering layer is larger than the A site / B site ratio of the other piezoelectric ceramic layers. ) Shows that the lifetime is improved. In each sample, since the stress relaxation layer is also driven, the amount of displacement is not impaired.
Therefore, according to this example, the A site / B site ratio of the insulation lowering layer is made larger than the A site / B site ratio of the other piezoelectric ceramic layers, thereby suppressing the reduction of the insulation resistance without impairing the displacement. It can be seen that the life of the multilayer piezoelectric element can be improved.

  Further, in the above-described example, the stress relaxation portion 11 is formed over the entire circumference of the side surface of the ceramic laminate 15 (see FIGS. 1 to 3). However, as shown in FIG. Alternately exposed stress relief portions can be formed in different layers. That is, for example, in the cross section of the ceramic laminate 15, the stress relaxation portions 11 exposed on one of the opposing side surfaces 151 can be alternately formed. Also in this case, the piezoelectric ceramic layer sandwiched between the internal electrode layers 13 and 14 and including the stress relaxation portion 11 becomes the stress relaxation layer 10a. When the internal electrode layer electrically connected to the side electrode 17 on the negative electrode side of the two internal electrode layers 13 and 14 adjacent to each other with the stress relaxation layer 10a interposed therebetween is defined as a reference electrode layer 14a, the reference electrode layer 14a Of the two piezoelectric ceramic layers 10a and 10b adjacent to each other, the piezoelectric ceramic layer that is not the stress relaxation layer 10a becomes the insulation lowering layer 10b. Even in this case, the A site / B site ratio of the insulation lowering layer 10b is made larger than the A site / B site ratio of the other piezoelectric ceramic layers 10 to suppress the reduction of the insulation resistance of the multilayer piezoelectric element. And the life can be improved. In FIG. 13, for convenience of drawing, the multilayer piezoelectric element 1 is shown in a form in which the actual number of layers is omitted.

Further, in this example, the internal electrode portions 131 and 141 and the stress relaxation portion 11 were formed in a combination pattern shown in FIG. The drawing shows a partially developed view of each piezoelectric ceramic layer 10 of the ceramic laminate 15. However, the present invention is not limited to this pattern. The ceramic laminate 15 is a region where all the internal electrode portions 131 are superposed and a region where only at least some of the internal electrode portions 131 are superposed or not superposed at all when the ceramic laminate 15 is viewed in the laminating direction. Although it has a certain non-polymerization part, the stress relaxation part 11 can be formed in the said non-polymerization part at least.
Variations of the combination pattern of the internal electrode portions 131 and 141 and the stress relaxation portion 1 are shown in FIGS. Even if it forms with any pattern, the effect of this invention is fully exhibited.

(Example 2)
This example is an example of a multilayer piezoelectric element in which the A site / B site ratio of the stress relaxation layer is larger than the A site / B site ratio of the other piezoelectric ceramic layers. The multilayer piezoelectric element of this example has the same configuration as that of the multilayer piezoelectric element of Example 1 except that the A site / B site ratio of the stress relaxation layer is increased.

That is, as shown in FIGS. 16 to 18, the multilayer piezoelectric element 2 of this example is formed by alternately laminating a plurality of piezoelectric ceramic layers 20 and a plurality of internal electrode layers 23 and 24 as in the first embodiment. And a pair of side electrodes 27 and 28 formed on the side surface in the direction perpendicular to the stacking direction. The piezoelectric ceramic layer 20 is mainly composed of a PZT material represented by the basic composition formula ABO ₃ . The internal electrode layers 23, 24 are conductive internal electrode portions 231, 241, and internal electrode non-formation regions whose outer peripheral end portions recede at a predetermined receding distance 235 inward from the outer peripheral surface of the ceramic laminate 25. The internal electrode layers 23 and 24 are electrically connected to alternately different side electrodes 27 and 28. In addition, the ceramic laminate 25 has a stress relaxation portion 21 whose shape can be changed more easily than the piezoelectric ceramic layer 20 in a slit-like region recessed inward from the side surface. Also in this example, as in the first embodiment, the stress relaxation portion 21 is a slit-like groove (space) recessed inward from the side surface 251 of the ceramic laminate 25, and the entire outer peripheral surface of the ceramic laminate 25. Is formed in the circumferential direction.

  In the multilayer piezoelectric element 2 of this example, when the piezoelectric ceramic layer 20 including the stress relaxation portion 21 is a stress relaxation layer 20a, the stress relaxation layer 20a has an A site / B site ratio as compared with the other piezoelectric ceramic layers 20. The main component is a large PZT material.

Next, a method for manufacturing the multilayer piezoelectric element of this example will be described with reference to FIGS. 4 to 7 and FIGS.
In this example, similarly to Example 1, the first sheet forming step, the second sheet forming step, the electrode material disposing step, the relaxing portion forming material disposing step, the laminating step, the firing step, and the side electrode forming step are performed. By doing so, a laminated piezoelectric element is manufactured.

In the first sheet forming step, a first green sheet 101 that contains a ceramic raw material and becomes a piezoelectric ceramic layer containing a PZT-based material represented by the basic composition formula ABO ₃ as a main component after firing is formed (FIG. 4 and FIG. 4). (See FIG. 5). Specifically, the first green sheet 101 is formed by forming a slurry-like or paste-like first ceramic raw material for producing a PZT-based material represented by the basic composition formula ABO ₃ after firing into a sheet shape.
Also in the second sheet forming step, a second green sheet 102 is formed which becomes a piezoelectric ceramic layer containing a ceramic raw material and containing the PZT material represented by the basic composition formula ABO ₃ as a main component after firing (FIG. 6). And FIG. 7). In the second sheet forming step, the composition of the second ceramic raw material is prepared so that the A site / B site ratio of the PZT material after firing is larger than that of the first green sheet. Is formed into a sheet shape to form the second green sheet 102.

  In the electrode material disposing step, as shown in FIGS. 4 to 7, the electrode materials 130 and 140 are formed on the portions where the internal electrode portions are formed in the printing region 103 on the first green sheet 101 and the second green sheet 102. The electrode arrangement sheets 105 and 106 are prepared by arranging. As a result, as shown in FIGS. 4 and 5, the first electrode placement sheet 105 in which the electrode materials 130 and 140 are placed on the first green sheet 101, and the second green as shown in FIGS. 6 and 7. A second electrode-disposed sheet 106 in which electrode materials 130 and 140 are disposed on the sheet 102 is obtained.

  Next, in the relaxation portion forming material disposing step, as shown in FIG. 19, a relaxation portion forming material 110 containing a disappearing material that disappears upon firing in a portion where the stress relaxation portion is formed on the second green sheet 102. Is provided to prepare the relaxation portion disposing sheet 107.

  In the laminating step, as shown in FIG. 20, a plurality of electrode arrangement sheets 105 and 106 are laminated, and a relaxation portion arrangement sheet 107 is laminated between the electrode arrangement sheets at an arbitrary interval in the lamination direction. The laminated body 20 (preliminary laminated body 200) is produced. At this time, the second electrode placement sheet 106 is laminated on the relaxation portion placement sheet 107 so that both of the two green sheets sandwiching the relaxation portion placement material 110 become the second green sheet 102, The first electrode disposition sheet 105 is disposed at other positions.

In the firing step, the intermediate laminate 20 is fired to produce the ceramic laminate 25 (see FIGS. 16 to 18).
In the side electrode forming step, the side electrodes 27 and 28 are formed by baking a conductive metal on the side surface of the ceramic laminate 25 (see FIGS. 16 to 18).
Hereafter, the manufacturing method of this example is demonstrated in detail for every process.

<First sheet forming step and second sheet forming step>
In the same manner as in Example 1, a first green sheet and a second green sheet having different A site / B site ratios were produced.

<Electrode material placement process>
Next, as in Example 1, electrode materials 130 and 140 are printed on the first green sheet 101 and the second green sheet 102 to produce the first electrode arrangement sheet 105 and the second electrode arrangement sheet 106. (See FIGS. 4 to 7).

<Relaxation part forming material arrangement process>
Next, as shown in FIG. 19, on the second green sheet 102, a relaxation portion forming material 110 containing a disappearing material that disappears by firing is printed on a predetermined region that will eventually become a stress relaxation portion. An arrangement sheet 107 was formed. The relaxing part forming material disposing step was performed in the same manner as in Example 1 except that the second green sheet 102 was used.

<Lamination process>
Next, as shown in FIG. 20, the first electrode arrangement sheet 105 was laminated. At this time, a plurality of first electrode arrangement sheets 105 are stacked so that the electrode material patterns 130 and 140 formed on the first electrode arrangement sheet are alternated, and the relaxation portion is formed at a position where the stress relaxation portion is to be formed. The arrangement sheet 107 was inserted and laminated. Specifically, in this example, the relaxing portion arrangement sheet 107 is laminated for every 11 layers of the laminated structure of the first electrode arrangement sheet 105. Further, at the time of lamination, the second green sheet 102 between which the two green sheets sandwiching the relaxation portion placement material 110 become both the second green sheets 102, and the first electrode placement sheet 105 is placed on the relaxation portion placement sheet 107. A two-electrode arrangement sheet 106 was laminated.
In this way, the first electrode arrangement sheet 105 and the second electrode arrangement sheet 106 are laminated so that there are a total of 59 sheets, and the electrode material and the relaxation portion forming material are printed on both ends in the lamination direction. No green sheet 101 (first green sheet) was laminated.
Next, the laminated sheets were heated at a temperature of 100 ° C., and pressed at 50 MPa in the laminating direction to produce a pre-laminated body 200. In FIG. 20, for the convenience of drawing creation, the preliminary laminated body 200 is shown in a form in which the actual number of laminated layers is omitted.

<Laminate cutting process>
Next, the pre-laminated body 200 was cut in the laminating direction along a predetermined cutting position 290 in the same manner as in Example 1 to produce the intermediate laminated body 20 (FIGS. 21 to 23). In this example, each intermediate laminate 20 was cut and cut so that the electrode materials 130 and 140 and the relaxing portion forming material 110 were exposed on the side surfaces of the intermediate laminate 20. In FIGS. 22 and 23, the preliminary laminated body 200 and the intermediate laminated body 20 are shown in a form in which the actual number of laminated layers is omitted for convenience of drawing.

  Next, the binder resin contained in the green sheet 101 (102) of the intermediate laminate 20 was removed by heating (degreasing). Heating was performed by gradually raising the temperature to 500 ° C. over 80 hours and holding for 5 hours.

<Baking process>
Next, the degreased intermediate laminate 20 was fired. In the same manner as in Example 1, firing was performed by gradually raising the temperature to 1050 ° C. over 12 hours, holding for 2 hours, and then gradually cooling.
In this way, the ceramic laminate 25 having the slit-like stress relaxation portion 21 formed by disappearing the relaxation portion forming material 110 is produced (see FIGS. 16 to 18). As shown in FIGS. 16 to 18, the stress relaxation portion 21 is provided with a slit-like space over the entire side surface of the ceramic laminate 25. Further, as shown in the figure, in the produced ceramic laminate 25, the internal electrode portions 231 and 241 formed by the piezoelectric ceramic layer 20 formed by sintering the first green sheet 101 and the electrode materials 130 and 140 are provided. The included internal electrode layers 23 and 24 are alternately stacked. Of the piezoelectric ceramic layers 20 sandwiched between the internal electrode layers 23 and 24, the piezoelectric ceramic layer 20a (stress relaxation layer 20a) including the stress relaxation portion 21 is formed by sintering the second green sheet 102.
And after baking, it grind | polished the whole surface and produced the ceramic laminated body 15 of length 6mm * width 6mm * height 4.4mm.

<Side electrode formation process>
Next, in the same manner as in Example 1, Ag electrodes were baked so as to sandwich both side surfaces of the ceramic laminate 25, and side electrodes 27 and 28 were formed. At this time, the internal electrode layers 23 and 24 are electrically connected to the side electrodes 27 and 28 on the side surfaces that are alternately different in the internal electrode portions 231 and 241, respectively.

As described above, the multilayer piezoelectric element 2 was produced as shown in FIGS.
In FIGS. 16 and 17, for convenience of drawing, the multilayer piezoelectric element 2 is shown in a form in which the actual number of layers is omitted.

In this example, ten types of laminated piezoelectric elements (samples Y1 to Y10) having different A-site / B-site ratios between the stress relaxation layer 20a and the other piezoelectric ceramic layers 20 were produced.
That is, the sample Y1 is the multilayer piezoelectric element 2 in which the A site / B site ratios of the stress relaxation layer and the other piezoelectric ceramic layers are all 1.01.
In the samples Y2 and Y3, the A site / B site ratio of the stress relaxation layer 20a is 1.005 and 1.002, respectively, and the A site / B site ratio of the other piezoelectric ceramic layers 20 other than the stress relaxation layer 20a is 1. .01 multilayer piezoelectric element 2.

In the samples Y4 to Y6, the A site / B site ratio of the stress relaxation layer 20a is 1.01, 1.005, and 1.002, respectively, and the A site / B of the other piezoelectric ceramic layers 20 other than the stress relaxation layer 20a. The multilayer piezoelectric element 2 has a B site ratio of 1.005.
In the samples Y7 to Y10, the A site / B site ratio of the stress relaxation layer 20a is 1.01, 1.005, 1.003, and 1.002, respectively, and the other piezoelectric ceramic layers 20 other than the stress relaxation layer 20a. The multilayer piezoelectric element 2 has an A site / B site ratio of 1.002.
The A site / B site ratio of the stress relaxation layer 20a in each sample (samples X1 to X10) and the A site / B site ratio of the other piezoelectric ceramic layers 20 are shown in Table 2 described later.

  Each sample Y1 to Y10 was subjected to a durability test in the same manner as in Example 1 to measure the lifetime. The results are shown in Table 2.

As is known from Table 2, the piezoelectric ceramic layers other than the stress relaxation layer have the same A site / B site ratio, that is, groups of sample Y1 to sample Y3, sample Y4 to sample Y6, and sample Y7 to sample Y10. Samples in which the A site / B site ratio of the stress relaxation layer is larger than the A site / B site ratio of the other piezoelectric ceramic layers (sample Y4 and samples Y7 to Y9) It can be seen that the lifetime is improved. In each sample, since the stress relaxation layer is also driven, the amount of displacement is not impaired.
Therefore, according to this example, the A site / B site ratio of the stress relaxation layer is made larger than the A site / B site ratio of the other piezoelectric ceramic layers, thereby suppressing a decrease in insulation resistance without impairing the displacement. It can be seen that the life of the multilayer piezoelectric element can be improved.

In the example of the multilayer piezoelectric element described above, the stress relaxation portion 21 is formed over the entire circumference of the side surface of the ceramic laminate 15, and the stress relaxation portion 21 is formed on the piezoelectric ceramic layer 20 (20a between the internal electrode layers 23 and 24). ) So as not to contact the internal electrode layers 23, 24 (see FIGS. 16 to 18). For example, as shown in FIG. 24, the stress relaxation portion 21 is substantially the same layer as the internal electrode layers 23, 24. Further, it can be formed so as to be in contact therewith. In this case, the stress relieving part 21 is not formed in the holding parts 232 and 242 in the internal electrode layers 23 and 24, but on the side where the internal electrode parts 231 and 241 and the side electrodes 27 and 28 are electrically connected. The stress relaxation part 21 exposed to the side surface can be formed.
Also in this case, the piezoelectric ceramic layer sandwiched between the internal electrode layers 23 and 24 and including the stress relaxation portion 11 becomes the stress relaxation layer 20a. In this case, the A site / B site ratio of the stress relaxation layer 20a is set to other piezoelectric layers. By making it larger than the A-site / B-site ratio of the ceramic layer 20, it is possible to suppress a decrease in the insulation resistance of the multilayer piezoelectric element and to improve the life. In FIG. 24, the stacked piezoelectric element 2 is shown in a form in which the actual number of stacked layers is omitted for the convenience of drawing.

Example 3
This example is an example of a multilayer piezoelectric element in which a stress relaxation portion is formed using a relaxation portion forming material containing a Pb oxide. In the multilayer piezoelectric element of this example, a stress relaxation part is formed using a relaxation part forming material containing a Pb oxide, and the insulation lowering layer and other piezoelectric ceramic layers are formed of a PZT material having the same composition. Except for, the configuration is the same as that of the first embodiment.

That is, as shown in FIGS. 25 to 27, in the multilayer piezoelectric element 3 of this example, a plurality of piezoelectric ceramic layers 30 and a plurality of internal electrode layers 33 and 34 are alternately stacked as in the first embodiment. And a pair of side surface electrodes 37 and 38 formed on the side surface in a direction perpendicular to the stacking direction. The piezoelectric ceramic layer 30 is mainly composed of a PZT material represented by the basic composition formula ABO ₃ . The internal electrode layers 33, 34 are conductive internal electrode portions 331, 341 and internal electrode non-formation regions in which outer peripheral end portions recede inward from the outer peripheral surface 351 of the ceramic laminate 35 by a predetermined receding distance. The internal electrode layers 33 and 34 are portions where the internal electrode portions 331 and 341 are exposed on the outer peripheral surface 351 of the multilayer body 35, and are electrically connected to alternately different side electrodes 37 and 38. ing. Moreover, the ceramic laminated body 35 has the stress relaxation part 21 which can change a shape more easily than the piezoelectric ceramic layer 30 in the slit-shaped area | region recessed inward from the side surface. Also in this example, as in the first embodiment, the stress relaxation portion 31 is a slit-like groove (space) recessed inward from the side surface 351 of the ceramic laminate 35, and the entire circumference of the outer peripheral surface of the ceramic laminate 35. Is formed in the circumferential direction.

  In the multilayer piezoelectric element 2 of this example, the stress relaxation part 31 is formed by firing a relaxation part forming material containing a Pb oxide in addition to the disappearance material. During firing, the disappearing material disappears to form slit-like groove portions (stress relaxation portions) and Pb diffuses around the slit-like groove portions. For this reason, it is considered that a PB rich region 315 having a higher Pb concentration than the surroundings is formed around the stress relaxation portion 31.

Next, a method for manufacturing the multilayer piezoelectric element of this example will be described with reference to FIGS. 4, 5, and 25 to 30.
In this example, a laminated piezoelectric element is manufactured by performing a sheet forming step, an electrode material disposing step, a relaxing portion forming material disposing step, a laminating step, a firing step, and a side electrode forming step.

In the sheet forming step, a green sheet that contains a ceramic raw material and becomes the piezoelectric ceramic layer after firing is formed. Specifically, a green sheet 101 is formed by forming a slurry-like or paste-like ceramic raw material for producing a PZT-based material represented by the basic composition formula ABO ₃ after firing into a sheet (see FIGS. 4 and 5). ).
In the electrode material disposing step, as shown in FIGS. 4 and 5, electrode materials 130 and 140 are disposed on the portion where the internal electrode portion is formed in the print region 103 on the green sheet 101 to form the electrode disposing sheet 105. Is made.
In the relaxation portion forming material disposing step, as shown in FIG. 28, the relaxing portion forming material 310 is disposed in the portion of the printing region 103 on the green sheet 101 where the stress relieving portion is to be formed, and the relaxation portion disposing sheet. 307 is produced. In this example, a material containing a disappearing material and a Pb oxide is adopted as the relaxation portion forming material 310.

Next, in the laminating step, as shown in FIGS. 29 and 30, a plurality of electrode arrangement sheets 105 are laminated, and a relaxing portion arrangement sheet 307 is provided between the electrode arrangement sheets 105 at an arbitrary interval in the lamination direction. Are laminated to produce an intermediate laminate 30 (preliminary laminate 300).
In the firing step, the intermediate laminate 30 is fired to produce the ceramic laminate 35 (see FIGS. 30 and 25 to 27).
In the side electrode forming step, the side electrodes 37 and 38 are formed by baking a conductive metal on the side surface of the ceramic laminate 35 (see FIGS. 25 to 27).
Hereafter, the manufacturing method of this example is demonstrated in detail for every process.

<Sheet formation process>
A green sheet 101 was produced in the same manner as the first green sheet of Example 1 (see FIGS. 4 and 5).

<Electrode material placement process>
Next, in the same manner as in Example 1, electrode materials 130 and 140 were printed on the green sheet 101 to produce the electrode-arranged sheet 105 (see FIGS. 4 and 5).

<Relaxation part forming material arrangement process>
Next, as shown in FIG. 29, in the printing region 103 on the first green sheet 101, the relaxation portion forming material 310 was printed in a predetermined region that finally becomes a stress relaxation portion. Thereby, the relaxation part arrangement | positioning sheet | seat 307 was formed. In this example, a paste-like material containing a disappearing material made of carbon particles and lead oxide (PbO) was used as the relaxing portion forming material 130.

<Lamination process>
Next, as shown in FIG. 29, the 1st electrode arrangement | positioning sheet | seat 105 was laminated | stacked, while heating at the temperature of 100 degreeC, it pressurized by 50 Mpa in the lamination direction, and the preliminary laminated body 300 was produced. At the time of lamination, a plurality of the first electrode arrangement sheets 105 were laminated so that the electrode material patterns 130 and 140 were alternated, and the relaxation portion arrangement sheet 307 was inserted and laminated at the position where the stress relaxation portion was to be formed. Specifically, in this example, the relaxing portion arrangement sheet 307 is laminated for every 11 layers of the laminated structure of the first electrode arrangement sheet 105. In this way, the first electrode-arranged sheets 105 were laminated so that the total number of sheets was 59, and the green sheets 101 on which the electrode material and the relaxing portion forming material were not printed were laminated at both ends in the lamination direction.

<Laminate cutting process>
Next, similarly to Example 1, the preliminary laminate 300 was cut in the stacking direction along a predetermined cutting position 390 to form the intermediate laminate 30 (see FIGS. 29 and 30).
In FIGS. 29 and 30, for the convenience of drawing, the preliminary laminated body 300 and the intermediate laminated body 30 are shown in a form in which the actual number of laminated layers is omitted.

  Next, the binder resin contained in the green sheet 101 or the like of the intermediate laminate 30 was removed by heating (degreasing). Heating was performed by gradually raising the temperature to 500 ° C. over 80 hours and holding for 5 hours.

<Baking process>
Next, the degreased intermediate laminate 30 was fired. In the same manner as in Example 1, firing was performed by gradually raising the temperature to 1050 ° C. over 12 hours, holding for 2 hours, and then gradually cooling. By this firing, the green sheet 101 is sintered to form the piezoelectric ceramic layer 30, and the internal electrode portions 331 and 341 are formed from the electrode materials 130 and 140 (see FIGS. 25 to 27). Further, the disappearance material of the relaxation portion forming material 310 disappears by firing to form the slit-shaped stress relaxation portion 31, and PbO to Pb contained in the relaxation portion formation material 310 changes the piezoelectric ceramic around the stress relaxation portion 31. Diffuses into layer 30.
And after baking, whole surface grinding | polishing was performed and the ceramic laminated body 35 of length 6mm * width 6mm * height 4.4mm was produced as shown in FIGS.

<Side electrode formation process>
Next, in the same manner as in Example 1, Ag electrodes were baked so as to sandwich both side surfaces of the ceramic laminate 35, and side electrodes 37 and 38 were formed. At this time, the internal electrode layers 33 and 34 are electrically connected to the side electrodes 37 and 38 on the side surfaces that are alternately different in the internal electrode portions 331 and 341, respectively.

As described above, the multilayer piezoelectric element 3 was produced as shown in FIGS.
25 and 26, the stacked piezoelectric element 3 is shown in a form in which the actual number of stacked layers is omitted for the convenience of drawing.

In this example, a plurality of stacked piezoelectric elements (samples Z2 to Z6) were manufactured by changing the blending ratio of PbO in the relaxing portion forming material in the relaxing portion forming material disposing step. For comparison, multilayer piezoelectric elements (sample Z7 and sample Z8) were prepared using a relaxing portion forming material containing ZrO ₂ in a predetermined blending ratio instead of PbO. For comparison, a multilayer piezoelectric element (sample Z1) was prepared using a relaxation portion forming material that contains only the disappearing material and does not contain an oxide additive.

That is, the sample Z1 is a multilayer piezoelectric element in which a stress relaxation portion is formed using a paste-like relaxation portion forming material that does not contain an oxide additive and contains only a disappearance material made of carbon. .
Samples Z2 to Z6 have a stress relaxation part using paste-like relaxation part forming materials containing 0.5, 1, 5, 10, and 20 parts by mass of PbO with respect to 100 parts by mass of the disappearing material made of carbon, respectively. It is a laminated piezoelectric element formed.
Samples Z7 and Z8 are laminated piezoelectric materials in which stress relaxation parts are formed using paste-like relaxation part forming materials containing 5 and 20 parts by mass of ZrO ₂ with respect to 100 parts by mass of the disappearing material made of carbon. It is an element.

For each sample (sample Z1 to sample Z8), the added amounts of PbO and ZrO ₂ used for the preparation are shown in Table 3 to be described later. In Table 3, the addition amount of PbO or ZrO ₂ indicates the addition amount (parts by mass) relative to 100 parts by mass of the disappearing material.

  About each sample Z1-Z8, the durability test was done similarly to Example 1, and the lifetime was measured. The results are shown in Table 3.

As is known from Table 3, it can be seen that the samples Z2 to Z6 prepared by adding PbO have an improved life compared to the sample Z1. In particular, Samples Z3 to Z5 prepared by adding 1 to 10 parts by mass of PbO with respect to 100 parts by mass of the disappearing material had a lifespan 2.5 times that of Sample Z1 and were greatly improved. .
On the other hand, in samples Z7 and Z8 produced by adding ZrO ₂ , the lifetime was reduced as compared with sample Z1.

In the multilayer piezoelectric element 3 of this example, each piezoelectric ceramic layer 30 is sandwiched between internal electrode layers 33 and 34 that are electrically connected to two different side electrodes 37 and 38, and is driven by voltage application. The displacement amount is not impaired (see FIGS. 25 to 27).
Therefore, according to this example, by forming the stress relaxation portion using the relaxation portion forming material obtained by adding PbO to the disappearing material, it is possible to suppress the decrease in the insulation resistance without impairing the amount of displacement. It can be seen that the life can be improved.

In this example, PbO was used as the Pb oxide, but other than these, Pb ₃ O ₄ , PT (lead titanate), PZ (lead zirconate), PZT (lead zirconate titanate), etc. Such a complex oxide of Pb can also be used.

DESCRIPTION OF SYMBOLS 1 Laminated piezoelectric element 10 Piezoelectric ceramic layer 10a Stress relaxation layer 10b Insulation lowering layer 11 Stress relaxation part 13 Internal electrode layer 13a Reference electrode layer 131 Internal electrode part 132 Internal electrode non-formation area 14 Internal electrode layer 141 Internal electrode part 142 Internal electrode Non-formation region 15 Ceramic laminate 17 Side electrode 18 Side electrode

Claims (11)

A ceramic laminate formed by alternately laminating a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers mainly composed of a PZT material represented by the basic composition formula ABO ₃ , and perpendicular to the laminating direction of the ceramic laminate In a laminated piezoelectric element having a pair of side electrodes formed on side surfaces in various directions,
The internal electrode layer includes a conductive internal electrode portion, and an internal electrode non-formation region in which an outer peripheral end portion of the internal electrode portion recedes inward from the outer peripheral surface of the ceramic laminate by a predetermined receding distance. And alternately electrically connected to any one of the side electrodes in the internal electrode portion,
The ceramic laminate has a slit-like stress relaxation portion that is recessed inward from the side surface of the ceramic laminate at a predetermined depth,
The piezoelectric ceramic layer including the stress relaxation portion is used as a stress relaxation layer, and is electrically connected to the side electrode on the negative electrode side of two internal electrode layers adjacent to each other with the stress relaxation layer sandwiched in the stacking direction of the ceramic laminate. When the internal electrode layer connected to the reference electrode layer is used as a reference electrode layer, and the two piezoelectric ceramic layers adjacent to each other with the reference electrode layer sandwiched between them are non-stress relaxation layers, the stress reduction layer And / or the insulation lowering layer is mainly composed of a PZT-based material having a larger A-site / B-site ratio than the other piezoelectric ceramic layers.   2. The A-site / B-site ratio of the PZT material constituting the piezoelectric ceramic layer is 1.005 or less in all the piezoelectric ceramic layers in the multilayer piezoelectric element according to claim 1. A laminated piezoelectric element characterized by the above.   3. The stress relaxation layer and / or the insulation lowering layer according to claim 1 or 2, wherein the A site / B site ratio is at least 0.001 or more as compared with the other piezoelectric ceramic layers. Multilayer piezoelectric element.   The retreat distance of the internal electrode non-formation region in the reference electrode layer according to any one of claims 1 to 3, wherein the stress existing closest to the reference electrode layer in the stacking direction of the stacked piezoelectric element. A laminated piezoelectric element characterized by being smaller than the depth of the relaxation portion. A ceramic laminate formed by alternately laminating a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers mainly composed of a PZT material represented by the basic composition formula ABO ₃ , and perpendicular to the laminating direction of the ceramic laminate In a laminated piezoelectric element having a pair of side electrodes formed on side surfaces in various directions,
The internal electrode layer includes a conductive internal electrode portion, and an internal electrode non-formation region in which an outer peripheral end portion of the internal electrode portion recedes inward from the outer peripheral surface of the ceramic laminate by a predetermined receding distance. And alternately electrically connected to any one of the side electrodes in the internal electrode portion,
The ceramic laminate has a slit-like stress relaxation portion that is recessed inward from the side surface of the ceramic laminate at a predetermined depth,
The multilayered piezoelectric element, wherein the stress relaxation part is formed by firing a relaxation part forming material containing a disappearing material that disappears upon firing and a Pb oxide.   In claim 5, the ceramic laminate includes a ceramic raw material, a sheet forming step of forming a green sheet that becomes the piezoelectric ceramic layer after firing, and a portion that forms the internal electrode portion on the green sheet, An electrode material disposing step of disposing an electrode material to produce an electrode disposing sheet, and disposing the relaxing portion by disposing the relaxing portion forming material on a portion where the stress relaxing portion is formed on the green sheet. A relaxation part forming material disposing step for producing a sheet, and a plurality of the electrode disposing sheets are laminated, and the relaxing part disposing sheets are laminated between the electrode disposing sheets with an arbitrary interval in the laminating direction, A laminate obtained by performing a laminating step for producing an intermediate laminate and a firing step for firing the intermediate laminate to produce the ceramic laminate. The piezoelectric element.   7. The multilayer piezoelectric element according to claim 5, wherein the relaxation portion forming material contains PbO as the Pb oxide.   The multilayer piezoelectric element according to any one of claims 5 to 7, wherein the relaxation portion forming material contains 20 parts by mass or less of Pb oxide in terms of PbO with respect to 100 parts by mass of the disappearing material. .   9. The internal electrode according to claim 5, wherein the piezoelectric ceramic layer including the stress relaxation portion is a stress relaxation layer, and the two internal electrodes adjacent to each other with the stress relaxation layer sandwiched in the stacking direction of the ceramic multilayer body. When the internal electrode layer electrically connected to the side electrode on the negative electrode side of the layer is a reference electrode layer, the receding distance of the internal electrode non-formation region in the reference electrode layer is the thickness of the multilayer piezoelectric element. A multilayer piezoelectric element characterized by being smaller than the depth of the stress relaxation portion existing closest to the reference electrode layer in the stacking direction.   10. The multilayer piezoelectric element according to claim 1, wherein the internal electrode portion contains an AgPd alloy as a main component.   11. The multilayer piezoelectric element according to claim 1, wherein the multilayer piezoelectric element is used for a fuel injection valve.

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