JP5141046B2 - Multilayer piezoelectric element - Google Patents

Description

  The present invention relates to a multilayer piezoelectric element used for a fuel injection device or the like.

Conventionally, a laminated body in which piezoelectric bodies and internal electrodes are alternately laminated, and an external electrode that is disposed on a side surface extending along the laminating direction of the laminated body and is electrically connected to the internal electrodes, A multilayer piezoelectric element is known in which a metal oxide layer (alumina layer) is disposed in the body so as to be the same layer as the layer in which an internal electrode is disposed (see, for example, Patent Document 1). ).
JP-A-5-243635

  In the laminated piezoelectric element, when a voltage is applied to the external electrode, a portion (active part) where the different internal electrodes of the piezoelectric body overlap each other when viewed from the lamination direction is deformed. For this reason, when driving a stacked piezoelectric element, a large stress concentration occurs at the boundary between the active region and the portion other than the active portion (inactive portion) in the piezoelectric body, and a crack (vertical crack) extending in the stacking direction of the stacked body occurs. It becomes easy to do. Therefore, in the conventional multilayer piezoelectric element described in Patent Document 1, the occurrence of vertical cracks is suppressed by relaxing the stress concentration by the metal oxide layer.

  However, when a metal oxide layer is disposed on the same layer as the internal electrode in the multilayer body as in the conventional multilayer piezoelectric element, vertical cracks are generated when the multilayer piezoelectric element is driven. There were times when it was inevitable. In this case, internal electrodes having different polarities may be short-circuited (short-circuited) to cause dielectric breakdown of the multilayer piezoelectric element.

  An object of the present invention is to provide a multilayer piezoelectric element capable of reliably preventing the occurrence of cracks (longitudinal cracks) extending in the stacking direction of a multilayer body.

  The multilayer piezoelectric element according to the present invention is configured by alternately laminating a plurality of piezoelectric bodies and a plurality of internal electrodes including a first internal electrode and a second internal electrode, and along the stacking direction of the piezoelectric bodies and the internal electrodes. A laminated body having a first side surface and a second side surface that extend, a metal oxide layer that is arranged in the laminated body and is made of a material having a melting point higher than the sintering temperature of the piezoelectric body, and arranged on the first side surface, A first external electrode electrically connected to the first internal electrode, a second external electrode disposed on the second side surface and electrically connected to the second internal electrode, and a first external electrode connected to the first external electrode 3 external electrodes and a fourth external electrode connected to the second external electrode, and the stacked body includes an active portion that is a portion where the first internal electrode and the second internal electrode overlap each other when viewed from the stacking direction. The first internal electrode and the second internal electrode overlap each other when viewed from the stacking direction. The metal oxide layer includes: a first region disposed in the inactive portion; a second region disposed in the active portion extending from the first region toward the active portion; The first external electrode has a connection surface that adheres to the first side surface and extends in the stacking direction, and the second external electrode has a connection surface that adheres to the second side surface and extends in the stacking direction. The third external electrode and the fourth electrode can be extended in the stacking direction.

  In the multilayer piezoelectric element according to the present invention, when a voltage is applied between the first internal electrode and the second internal electrode, an electric field is generated between the first internal electrode and the second internal electrode, A portion present in the active portion is displaced in the stacking direction of the stacked body. At this time, concentrated stress due to the displacement of the piezoelectric body is generated in the inactive portion of the multilayer body. However, the laminated body is provided with a metal oxide layer formed of a material having a melting point higher than the sintering temperature of the piezoelectric body. Therefore, when the multilayer body is fired in the manufacturing process of the multilayer piezoelectric element, the metal oxide layer is not sufficiently sintered as compared with the piezoelectric body. Therefore, the metal oxide layer has a lower strength than the piezoelectric body. As a result, cracks (lateral cracks) are likely to enter along the metal oxide layer, and it is possible to reliably prevent the occurrence of cracks (vertical cracks) extending in the stacking direction of the laminate. Further, the metal oxide layer has a first region disposed in the inactive portion of the stacked body and a second region disposed in the active portion extending from the first region to the active portion side. For this reason, the concentrated stress generated in the inactive portion when the multilayer piezoelectric element is displaced is alleviated by the metal oxide layer, and the concentrated stress is applied to the end portion of the internal electrode located at the boundary between the active portion and the inactive portion. It is difficult, and the internal electrode and the piezoelectric body remain integrated. As a result, it is also possible to reliably prevent the occurrence of fine cracks (microcracks) that tend to occur from the end of the internal electrode located at the boundary between the active part and the inactive part.

  The first external electrode and the second external electrode layer are preferably metal strips.

  The first external electrode includes a first electrode layer that is a metal strip and a second electrode layer formed of a resin material containing conductive particles, and the second external electrode is made of metal. A first electrode layer that is a belt-like body and a second electrode layer formed of a resin material containing conductive particles, and the first electrode layer of the first external electrode adheres to the first side surface, The second electrode layer of one external electrode is connected to the third external electrode, the first electrode layer of the second external electrode is attached to the second side surface, and the second electrode layer of the second external electrode is the fourth external electrode It is preferable that it is connected with. This makes it possible to ensure electrical connection between the first external electrode and the third external electrode via the second electrode layer of the first external electrode, and It is possible to ensure electrical connection between the second external electrode and the fourth external electrode via the second electrode layer.

  The third external electrode and the fourth external electrode are preferably flat. In this way, it is possible to reduce the size of the multilayer piezoelectric element. In addition, the electrical resistance value can be reduced as compared with a mesh electrode in which a large number of fine lines arranged in a mesh pattern are connected to each other at their intersections. Further, since the contact area between the first external electrode and the second external electrode is larger than that of the mesh electrode, the electrical resistance value can be further reduced, and the first external electrode and the second external electrode can be reduced. The connection strength with the electrode can be improved. In addition, since the deformation is less than that of the mesh-like electrode which is very easily deformed, positioning and connection can be easily performed when connecting the first external electrode and the second external electrode. Become.

  The third external electrode has a first portion that is discontinuously arranged in the stacking direction, and a second portion that extends in a direction intersecting the stacking direction and connects the first portions, and the fourth external electrode is It is preferable to have a first portion that is discontinuously arranged in the stacking direction and a second portion that extends in a direction crossing the stacking direction and connects the first portions. In this case, since the third external electrode has the first part and the second part, and the fourth external electrode has the first part and the second part, it simply extends linearly in the stacking direction. Compared to the external electrode, it is possible to further suppress the displacement of the multilayer piezoelectric element in the stacking direction, and the external electrode is not affected even when the multilayer piezoelectric element is continuously driven for a long time. It becomes possible to suppress disconnection.

  The third external electrode has a first portion that is discontinuously arranged in the stacking direction, and a second portion that extends in a direction intersecting the stacking direction and connects the first portions, and the fourth external electrode is The first external electrode includes a first portion disposed discontinuously in the stacking direction, and a second portion extending in a direction crossing the stacking direction and connecting the first portions, and the first external electrode is a third external electrode. The second external electrode is preferably connected to the second part of the fourth external electrode. In this case, since the third external electrode has the first part and the second part, and the fourth external electrode has the first part and the second part, it simply extends linearly in the stacking direction. Compared to the external electrode, it is possible to further suppress the displacement of the multilayer piezoelectric element in the stacking direction, and the external electrode is not affected even when the multilayer piezoelectric element is continuously driven for a long time. It becomes possible to suppress disconnection. The first external electrode is connected to the second portion of the third external electrode extending in the direction intersecting the stacking direction, and the second external electrode is connected to the second portion of the fourth external electrode extending in the direction crossing the stacking direction. The first portion of the third external electrode that is likely to extend in the stacking direction and the first portion of the fourth external electrode that is likely to extend in the stacking direction are constrained by the first external electrode and the second external electrode. Absent. Therefore, it is possible to further suppress the inhibition of the displacement in the stacking direction of the stacked piezoelectric element.

  The second electrode layer of the first external electrode is connected to the second part of the third external electrode, and the second electrode layer of the second external electrode is connected to the second part of the fourth external electrode. Is preferred.

  Further, it is preferable that the second portion of the third external electrode and the second portion of the fourth external electrode do not overlap with a virtual plane including the metal oxide layer. In this case, the metal oxide layer and the inactive portion around the metal oxide layer are formed by the second portion of the third external electrode extending in the direction crossing the stacking direction and the second portion of the fourth external electrode extending in the direction crossing the stacking direction. Therefore, the concentrated stress generated in the inactive portion can be more effectively reduced.

  The first portion of the third external electrode and the first portion of the fourth external electrode preferably extend in the stacking direction.

  Further, in the laminate, the first region of the metal oxide layer is disposed so as to be the same layer as the layer where the internal electrode is disposed, and the metal is overlapped with at least a part of the internal electrode. The second region of the oxide layer is preferably disposed. In this way, it is not necessary to use more material than necessary to form the metal oxide layer. Therefore, the material cost of the metal oxide layer can be saved, and the time required for manufacturing the multilayer piezoelectric element can be shortened. The term “the same layer as the internal electrode” here is not limited to a layer that is completely the same as the internal electrode, but includes a layer that is substantially the same as the internal electrode.

  Further, in the laminate, the first region of the metal oxide layer is disposed so as to be the same layer as the layer in which the internal electrode is disposed, and the metal oxide layer is overlapped with the entire internal electrode. The second region is preferably arranged. In this way, the strength of the interface between the piezoelectric body and the internal electrode is further reduced. Therefore, it is possible to make it easier to generate a lateral crack along the interface between the piezoelectric body and the internal electrode.

The piezoelectric body is made of a piezoelectric material mainly composed of lead zirconate titanate, and the metal oxide layer is made of ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , Y ₂ O _3. It is preferable to be formed of a material containing at least one of the above. ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O ₃ are materials that have a melting point higher than the sintering temperature of lead zirconate titanate and can be dissolved in lead zirconate titanate. It is. Therefore, by using these materials for the metal oxide layer, when the laminate is fired, the components of the metal oxide layer are less likely to precipitate at the grain boundaries of the piezoelectric body, and the unit thickness of the piezoelectric body An increase in the number of hit grain boundaries is suppressed. Therefore, it is easy to suppress heat loss that occurs at the grain boundary of the piezoelectric body when a voltage (electric field) is applied between the first internal electrode and the second internal electrode. As a result, it is possible to obtain a desired displacement with respect to the applied electric field when the stacked piezoelectric element is displaced. Further, since the number of grain boundaries per unit thickness in the piezoelectric body is reduced, it is possible to further suppress the occurrence of vertical cracks in the laminated body.

  ADVANTAGE OF THE INVENTION According to this invention, the lamination type piezoelectric element which can prevent reliably generation | occurrence | production of the crack extended in the lamination direction of a laminated body can be provided.

  Preferred embodiments of the present invention will be described with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and a duplicate description is omitted. The multilayer piezoelectric element according to the present invention is used, for example, in a fuel injection device for an internal combustion engine mounted on an automobile.

(First embodiment)
The configuration of the multilayer piezoelectric element E1 according to the first embodiment will be described with reference to FIGS. FIG. 1 is a perspective view showing the multilayer piezoelectric element according to the first embodiment. FIG. 2 is a longitudinal sectional view showing the multilayer piezoelectric element according to the first embodiment. FIG. 3 is an enlarged longitudinal sectional view showing a part of the multilayer piezoelectric element according to the first embodiment.

  The multilayer piezoelectric element E1 includes a multilayer body 2 having a polygonal column shape (a quadrangular column shape in the first embodiment). The multilayer body 2 is configured by laminating a plurality of piezoelectric bodies 3 and a plurality of internal electrodes 4A and 4B in a predetermined order. The stacked body 2 has side surfaces 2a and 2b that are parallel to the stacking direction and face each other. For example, the laminate 2 can be set to have a width of about 10 mm, a depth of about 10 mm, and a height of about 35 mm.

The piezoelectric body 3 is made of, for example, a piezoelectric ceramic material mainly composed of PZT (lead zirconate titanate). The thickness of the piezoelectric body 3 is, for example, about 80 μm to 100 μm per layer. As a composition of PZT, the following are used, for example.
Pb0.999 [(Zn _1/3 Nb _2/3 ) 0.11Ti0.425 Zr0.465] O ₃ + 0.2wt% Fe ₂ O ₃ + 0.2wt% Sb ₂ O ₃

As the powder characteristics of PZT, for example, those having a BET specific surface area of about 2.5 m ² / g and an average particle diameter of about 0.6 μm are used. The sintering temperature of PZT is about 950 ° C. The melting point of the PZT material is about 1300 ° C.

  The internal electrodes 4A and 4B are made of a conductive material containing Ag and Pd as main components, for example. The thickness of the internal electrodes 4A and 4B can be set to about 2 μm, for example. The internal electrodes 4A and 4B are alternately stacked with the piezoelectric body 3 interposed therebetween. One end of the internal electrode 4 </ b> A is exposed on the side surface 2 a of the multilayer body 2. The other end of the internal electrode 4 </ b> A is located inside the side surface 2 b of the multilayer body 2. One end of the internal electrode 4B is exposed on the side surface 2b of the multilayer body 2. The other end of the internal electrode 4 </ b> B is located inside the side surface 2 a of the multilayer body 2. Thereby, a part of the internal electrodes 4 </ b> A and 4 </ b> B overlaps in the stacking direction of the stacked body 2.

  In the multilayer body 2, the portions where the internal electrodes 4 </ b> A and 4 </ b> B overlap in the stacking direction are active portions P in which the piezoelectric body 3 is displaced when a voltage is applied to the internal electrodes 4 </ b> A and 4 </ b> B. The portions where 4B does not overlap in the stacking direction (both ends of the stacked body 2) are inactive portions Q where the piezoelectric body 3 is not displaced when a voltage is applied to the internal electrodes 4A and 4B.

  A plurality of metal oxide layers 5 having electrical insulation and lower density (strength) than the piezoelectric body 3 are formed on the laminate 2. The metal oxide layer 5 includes a region 5a formed in the same layer as the internal electrodes 4A and 4B in the inactive portion Q, and an upper surface of a part of the internal electrodes 4A and 4B extending from the region 5a to the active portion P side. And a region 5b formed so as to overlap (see FIG. 3). The region 5a located in the same layer as the internal electrode 4A is exposed on the side surface 2b of the multilayer body 2, and the region 5a located in the same layer as the internal electrode 4B is exposed on the side surface 2a of the multilayer body 2. That is, the metal oxide layer 5 extends from the side surfaces 2a and 2b of the multilayer body 2 to the active portion P so as to be in contact with the internal electrodes 4A and 4B. The thickness of the region 5a is, for example, the same thickness as the internal electrodes 4A and 4B.

The metal oxide layer 5 is formed of a material that has a melting point higher than the sintering temperature of PZT, which is the main component of the piezoelectric body 3, and is solid-solved in PZT. Examples of such a material include a material containing at least one of ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O ₃ . That is, the metal oxide layer 5 and the piezoelectric body 3 are formed of materials having different composition systems. Note that the melting points of ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O ₃ are about 1500 ° C. to 2800 ° C.

  External electrodes 6 </ b> A and 10 </ b> A are provided on the side surface 2 a of the multilayer body 2. The external electrode 6A has an electrode layer 7a and an electrode layer 8a. The electrode layer 7a is a substantially rectangular belt-like body, and covers the central portion of the side surface 2a and is attached to the side surface 2a so as to extend in the stacking direction. Therefore, the electrode layer 7a is electrically connected to each internal electrode 4A exposed on the side surface 2a on the side surface 2a. The electrode layer 7a is made of a conductive material containing, for example, one of Ag, Au and Cu as a main component. The thickness of the electrode layer 7a can be set to about 1 μm to 20 μm, for example.

  The electrode layer 8a is obtained by solidifying a conductive adhesive in which, for example, Ag conductive particles are dispersed in an adhesive resin material. The electrode layer 8a includes a first portion 8aa and a second portion 8ab. The first portion 8aa has a substantially rectangular shape, and covers the central portion of the electrode layer 7a and is attached to the electrode layer 7a so as to extend in the stacking direction. The second portion 8ab has a substantially rectangular shape, and covers the first portion 8aa and adheres to the first portion 8aa so as to extend in the stacking direction. The thickness of the first portion 8aa and the second portion 8ab of the electrode layer 8a can be set to about 30 μm to 60 μm, respectively.

  The external electrode 10A has a first portion 11a and a second portion 12a. The first portion 11a extends in the stacking direction and is discontinuously arranged in the stacking direction. The second portion 12a extends in a direction intersecting the stacking direction (orthogonal direction in the first embodiment), and connects the first portions 11a. Therefore, in the first embodiment, the external electrode 10A has a crank shape and can be expanded and contracted in the stacking direction. 10 A of external electrodes are flat form, for example, are formed with Cu, Cu alloy, Ni, Ni alloy, a flexible substrate, etc. In the first embodiment, the thickness of the external electrode 10A can be set to about 150 μm, for example.

  The external electrode 10A is fixed to the electrode layer 8a (see FIGS. 1 and 2). Specifically, the external electrode 10A is provided on the electrode layer 8a so that a part of the second portion 12a is buried in the second portion 8ab of the electrode layer 8a and the first portion 11a is not in contact with the electrode layer 8a. Yes. Further, the external electrode 10A has the second portion 12a and the metal oxide layer 5 when viewed from a direction orthogonal to the side surface 2a so that the second portion 12a does not overlap the virtual plane including the metal oxide layer 5. It arrange | positions so that the 1st part 11a may overlap with the metal oxide layer 5 without overlapping.

  External electrodes 6 </ b> B and 10 </ b> B are provided on the side surface 2 b of the multilayer body 2. The external electrode 6B has an electrode layer 7b and an electrode layer 8b. The electrode layer 7b is a substantially rectangular belt-like body, and covers the central portion of the side surface 2b and adheres to the side surface 2b so as to extend in the stacking direction. Therefore, the electrode 7b is electrically connected to each internal electrode 4B exposed on the side surface 2b on the side surface 2b. The electrode layer 7b is made of a conductive material containing, for example, one of Ag, Au, and Cu as a main component. The thickness of the electrode layer 7b can be set to about 1 μm to 20 μm, for example.

  The electrode layer 8b is obtained by solidifying a conductive adhesive in which, for example, Ag conductive particles are dispersed in an adhesive resin material. The electrode layer 8b includes a first portion 8ba and a second portion 8bb. The first portion 8ba has a substantially rectangular shape, and covers the central portion of the electrode layer 7b and adheres to the electrode layer 7b so as to extend in the stacking direction. The second portion 8bb has a substantially rectangular shape, and covers the first portion 8ba and adheres to the first portion 8ba so as to extend in the stacking direction. The thickness of the first portion 8ba and the second portion 8bb of the electrode layer 8b can be set to about 30 μm to 60 μm, respectively.

  The external electrode 10B has a first portion 11b and a second portion 12b. The first portion 11b extends in the stacking direction and is discontinuously arranged in the stacking direction. The second portion 12b extends in a direction intersecting with the stacking direction (orthogonal direction in the first embodiment), and connects the first portions 11b. Therefore, in the first embodiment, the external electrode 10B has a crank shape and can be expanded and contracted in the stacking direction. The external electrode 10B has a flat plate shape, and is formed of, for example, Cu, Cu alloy, Ni, Ni alloy, a flexible substrate, or the like. In the first embodiment, the thickness of the external electrode 10B can be set to about 150 μm, for example.

  The external electrode 10B is fixed to the electrode layer 8b (see FIGS. 1 and 2). Specifically, the external electrode 10B is provided on the electrode layer 8b so that a part of the second portion 12b is buried in the second portion 8bb of the electrode layer 8b and the first portion 11b does not contact the electrode layer 8b. Yes. In addition, the external electrode 10B has the second portion 12b and the metal oxide layer 5 so that the second portion 12b does not overlap the virtual plane including the metal oxide layer 5, that is, when viewed from the direction orthogonal to the side surface 2b. It arrange | positions so that the 1st part 11b may overlap with the metal oxide layer 5 without overlapping.

  Next, with reference to FIGS. 4 and 5, a method for manufacturing the multilayer piezoelectric element E1 having the above-described configuration will be described. FIG. 4 is a view for explaining the method for manufacturing the multilayer piezoelectric element according to the first embodiment. FIG. 5 is an exploded perspective view for explaining the configuration of the element body included in the multilayer piezoelectric element according to the first embodiment.

  First, a paste for a green sheet is prepared by mixing an organic binder resin and an organic solvent with ceramic powder containing PZT as a main component. Then, a plurality of green sheets 21 for forming the piezoelectric body 3 are formed by applying a paste for green sheets on a carrier film (not shown) by, for example, a doctor blade method.

  Subsequently, for example, an electrode pattern paste is prepared by mixing an organic binder resin, an organic solvent, and the like with a conductive material having a ratio of Ag: Pd = 85: 15. Then, as shown in FIG. 4A, the electrode patterns 22A and 22B corresponding to the internal electrodes 4A and 4B are respectively formed on the separate green sheets 21 by screen printing the electrode pattern paste, for example. Form. At this time, electrode patterns 22 </ b> A and 22 </ b> B are formed in a region excluding one end portion corresponding to the inactive portion Q on the upper surface of the green sheet 21.

Subsequently, for example, a ZrO ₂ paste in which an organic binder resin, an organic solvent, and the like are mixed with ceramic powder containing ZrO ₂ powder is prepared. Incidentally, the particle diameter of the ZrO ₂ powder used is greater than the particle diameter of the piezoelectric material powder (ceramic powder), the electrode pattern 22A, is preferably smaller than the thickness of 22B.

Then, as shown in FIG. 4B, the ZrO ₂ paste layer 23 is formed on the green sheet 21 and the electrode patterns 22A and 22B by screen printing the ZrO ₂ paste, for example. At this time, the ZrO ₂ paste layer 23 is formed in the electrode non-printed area (area corresponding to the inactive portion Q) on the upper surface of the green sheet 21 where the electrode patterns 22A and 22B are not printed, and the electrode patterns 22A and 22B The ZrO ₂ paste layer 23 is formed so as to overlap the end region on the upper surface of the electrode unprinted region side.

Subsequently, as shown in FIG. 5, the green sheet 21 on which the electrode pattern 22A and the ZrO ₂ paste layer 23 are formed and the green sheet 21 on which the electrode pattern 22B and the ZrO ₂ paste layer 23 are formed are arranged in a predetermined order. Laminate with. Then, a predetermined number of green sheets 21 on which the electrode patterns 22A and 22B and the ZrO ₂ paste layer 23 are not formed are stacked on the outermost layer as a protective layer. Thereby, the green laminated body 24 is formed.

  Subsequently, the green laminated body 24 is pressed in the laminating direction while being heated at a temperature of about 60 ° C., and then the green laminated body 24 is cut into a predetermined size by, for example, a diamond blade to form a chip.

Subsequently, the cut green laminate 24 is placed on a setter (not shown), and the green laminate 24 is degreased (debindered) at a temperature of about 400 ° C. for about 10 hours. And the green laminated body 24 after degreasing | defatting is put in a mortar furnace, and the green laminated body 24 is baked for about 2 hours, for example under the temperature of 950 to 1000 degreeC. Thus, the green sheet 21, the electrode patterns 22A, 22B and ZrO ₂ paste layer 23 is sintered laminate 2 as a sintered body is obtained.

At this time, since the ZrO ₂ paste layer 23 is made of a material having a composition different from that of the green sheet 21, the sintering reactivity between the ZrO ₂ paste layer 23 and the green sheet 21 is suppressed, and unnecessary chemicals are used between them. There is no reaction. Moreover, since the melting point of ZrO ₂ paste layer 23 is higher than the sintering temperature of the green sheet 21, ZrO ₂ paste layer 23 is sintered in comparison with the green sheet 21 hardly. For this reason, after sintering, the ZrO ₂ paste layer 23 becomes the metal oxide layer 5 having low bonding strength with the piezoelectric body 3.

  The metal oxide layer 5 has the region 5a and the region 5b as described above, but the thickness of the region 5b overlapping the internal electrodes 4A and 4B is reduced to the region 5a due to the shrinkage of the green laminated body 24 due to firing. It will be thinner than the thickness.

  Subsequently, external electrodes 6A and 6B and external electrodes 10A and 10B are formed on the side surfaces 2a and 2b of the multilayer body 2, respectively. Specifically, for example, a conductive paste containing Ag as a main component is screen-printed on the side surfaces 2a and 2b of the laminate 2 and a baking process is performed at a temperature of about 700 ° C. Electrode layers 7a and 7b are formed on 2a and 2b, respectively. Here, as a method of forming the electrode layers 7a and 7b, a sputtering method or an electroless plating method may be used.

  Then, for example, the first portions 8aa and 8ba of the electrode layers 8a and 8b are formed by applying and solidifying a conductive adhesive containing conductive particles mainly composed of Ag on the electrode layers 7a and 7b, respectively. To do. Similarly, after applying the conductive adhesive to the first portions 8aa and 8ba, respectively, and attaching the external electrodes 10A and 10B to the conductive adhesive applied to the first portions 8aa and 8ba, respectively, the first portions 8aa , 8ba is solidified to form the second portions 8ba, 8bb of the electrode layer 8a, and the external electrodes 10A, 10B are fixed to the electrode layer 8a. The external electrodes 10A and 10B can be obtained, for example, by processing a plate material made of beryllium copper into a crank shape and performing Ni plating and Su plating.

  Finally, the polarization treatment is performed by applying a predetermined voltage, for example, for 3 minutes at a temperature of 120 ° C., for example, so that the electric field strength in the thickness direction of the piezoelectric body 3 is about 2 kV / mm. Thus, the multilayer piezoelectric element E1 is completed.

  By the way, in the laminated piezoelectric element, when a voltage is applied to the external electrode, a portion (active part) where the internal electrodes having different polarities overlap each other when viewed from the lamination direction in the piezoelectric body is deformed. For this reason, when driving a stacked piezoelectric element, a large stress concentration occurs at the boundary between the active region and the portion other than the active portion (inactive portion) in the piezoelectric body, and a crack (vertical crack) extending in the stacking direction of the stacked body occurs. It becomes easy to do. Therefore, conventionally, various measures have been taken to suppress the occurrence of vertical cracks. Specifically, as measures to suppress the occurrence of vertical cracks, (1) in the direction crossing the stacking direction There are known methods for intentionally generating extending cracks (lateral cracks), and (2) methods for forming cracks extending in the direction intersecting the stacking direction (lateral cracks) in a desired location in advance.

  As a method for intentionally generating a lateral crack, for example, (1a) a method of using a concentrated stress generated in a point-bonded portion of the laminate by externally bonding the external electrode to the laminate with solder or the like, 1b) There is a method of providing a weak portion in the laminate. However, in these methods, lateral cracks are generated randomly, so that there is a problem that longitudinal cracks that cause problems such as dielectric breakdown of the multilayer piezoelectric element may occur.

  On the other hand, as a method of forming a lateral crack in a desired place in advance, for example, (2a) a method of forming a slit that is a pseudo lateral crack in a desired place by machining, or (2b) firing of a laminate In this case, there is a method of forming a metal oxide layer or the like having a lower strength than the piezoelectric body in the laminated body. However, the method by machining has a problem that the cost is very high and it is not suitable for mass production. In the method of forming the metal oxide layer in the stacked body, the metal oxide layer is conventionally disposed in the same layer as the layer in which the internal electrode is disposed in the stacked body. There is a problem in that fine cracks (microcracks) are generated from the end of the internal electrode located at the boundary between the two.

  However, in the present embodiment, the laminated body 2 is provided with the metal oxide layer 5 formed of a material having a melting point higher than the sintering temperature of the piezoelectric body 3. Therefore, when the multilayer body 2 is fired in the manufacturing process of the multilayer piezoelectric element E1, the metal oxide layer 5 is not sufficiently sintered as compared with the piezoelectric body 3. Therefore, the metal oxide layer 5 has a lower strength than the piezoelectric body 3. As a result, cracks (lateral cracks) are likely to occur along the metal oxide layer 5, and it is possible to reliably prevent the occurrence of cracks (vertical cracks) extending in the stacking direction of the stacked body 2. The metal oxide layer 5 has a region 5a disposed in the inactive portion Q of the stacked body 2 and a region 5b disposed in the active portion P extending from the region 5a to the active portion P side. . Therefore, the concentrated stress generated in the inactive portion Q when the multilayer piezoelectric element E1 is displaced is relieved by the metal oxide layer 5, and the internal electrodes 4A and 4B located at the boundary between the active portion P and the inactive portion Q are relaxed. The concentrated stress is not easily applied to the end of the inner electrode 4A, and the internal electrodes 4A and 4B and the piezoelectric body 3 remain integrated. As a result, it is possible to reliably prevent the occurrence of fine cracks (microcracks) that tend to occur from the end portions of the internal electrodes 4A and 4B located at the boundary between the active portion P and the inactive portion Q.

  Moreover, in this embodiment, the electrode layers 7a and 7b formed by screen-printing and baking the conductive paste on the side surfaces 2a and 2b of the multilayer body 2 are attached to the side surfaces 2a and 2b, respectively. . Therefore, the displacement of the multilayer body 2 is restricted by the external electrodes 10A and 10B through the connection surfaces of the electrode layers 7a and 7b when the multilayer piezoelectric element E1 is displaced. Therefore, the stress generated in the stacked body 2 due to the constraint of the external electrodes 10A and 10B is uniformly dispersed. As a result, it is possible to reliably prevent the occurrence of unexpected cracks in the laminate 2.

  Further, in the present embodiment, the external electrodes 10A and 10B can be expanded and contracted in the stacking direction. Therefore, it is possible to suppress the displacement of the stacked piezoelectric element E1 in the stacking direction.

  Therefore, in the multilayer piezoelectric element E1 according to the present embodiment, (1) generation of microcracks and vertical cracks can be reliably prevented, and (2) occurrence of unexpected cracks in the multilayer body 2 is ensured. While being able to prevent, (3) it can suppress that the displacement in the lamination direction of lamination type piezoelectric element E1 is inhibited. Therefore, according to the present invention, it is also possible to provide the multilayer piezoelectric element E1 with extremely high reliability while ensuring a sufficient amount of displacement.

  Further, in the present embodiment, the external electrode 6A has an electrode layer 7a that is a metal strip and an electrode layer 8a that is solidified with a conductive adhesive, and the external electrode 6B is a metal strip. And an electrode layer 8b in which the conductive adhesive is solidified. The electrode layer 7a of the external electrode 6A is attached to the side surface 2a, the electrode layer 8a of the external electrode 6A is connected to the external electrode 10A, the electrode layer 7b of the external electrode 6B is attached to the side surface 2b, and the external electrode 6B The electrode layer 8b is connected to the external electrode 10B. Therefore, it is possible to ensure electrical connection between the external electrode 6A and the external electrode 10A via the electrode layer 8a of the external electrode 6A, and the external electrode via the electrode layer 8b of the external electrode 6B. The electrical connection between 6B and the external electrode 10B can be ensured.

  In the present embodiment, the external electrodes 10A and 10B have a flat plate shape. Therefore, it is possible to reduce the size of the multilayer piezoelectric element E1. In addition, the electrical resistance value can be reduced as compared with a mesh electrode in which a large number of fine lines arranged in a mesh pattern are connected to each other at their intersections. Further, since the contact area with the external electrodes 10A and 10B is larger than that of the mesh electrode, the electrical resistance value can be further reduced and the connection strength with the external electrodes 10A and 10B can be improved. It becomes possible to plan. Further, since the deformation is less than that of the mesh-like electrode which is very easily deformed, positioning and connection can be easily performed when connecting to the external electrodes 10A and 10B.

  In the present embodiment, the external electrode 10A includes a first portion 11a that is discontinuously arranged in the stacking direction, and a second portion 12a that extends in the direction intersecting the stacking direction and connects the first portions 11a. Have. The external electrode 10B includes a first portion 11b that is discontinuously arranged in the stacking direction, and a second portion 12b that extends in a direction intersecting the stacking direction and connects the first portions 11b. Therefore, the external electrode 10A has the first portion 11a and the second portion 12a, and the external electrode 10B has the first portion 11b and the second portion 12b. Therefore, the external electrode simply extends linearly in the stacking direction. Compared with the electrode, it is possible to further suppress the displacement of the stacked piezoelectric element E1 in the stacking direction, and the external electrode even when the stacked piezoelectric element E1 is continuously driven for a long time. It is possible to suppress disconnection of 10A and 10B.

  In the present embodiment, the second portion 8ab of the electrode layer 8a in the external electrode 6A is connected to the second portion 12a of the external electrode 10A, and the second portion 8bb of the electrode layer 8b in the external electrode 6B is connected to the external electrode. 10B is connected to the second portion 12b. Therefore, the first portion 11a of the external electrode 10A that easily extends in the stacking direction and the first portion 11b of the external electrode 10B that easily extends in the stacking direction are not restrained by the external electrodes 6A and 6B. Therefore, it is possible to further suppress the inhibition of the displacement in the stacking direction of the stacked piezoelectric element E1.

  In the present embodiment, the second portion 12a of the external electrode 10A and the second portion 12b of the external electrode 10B are not overlapped with a virtual plane including the metal oxide layer 5. Therefore, the metal oxide layer 5 and the inactive portion Q around the metal oxide layer 5 are formed by the second portion 12a of the external electrode 10A extending in the direction crossing the stacking direction and the second portion 12b of the external electrode 10B extending in the direction crossing the stacking direction. Since it is not restrained, the concentrated stress generated in the inactive portion Q can be more effectively relaxed.

  Further, in this embodiment, the region 5a of the metal oxide layer 5 is disposed in the multilayer body 2 so as to be the same layer as the layer in which the internal electrodes 4A and 4B are disposed, and the internal electrode 4A. , 4B, the region 5b of the metal oxide layer 5 is arranged so as to overlap with at least a part of it. Therefore, it is not necessary to use more material than necessary to form the metal oxide layer 5. As a result, the material cost of the metal oxide layer 5 can be saved, and the time required for manufacturing the multilayer piezoelectric element E1 can be shortened.

In the present embodiment, the piezoelectric body 3 is formed of a piezoelectric material mainly composed of lead zirconate titanate, and the metal oxide layer 5 is formed of ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O _5. , CeO ₂ , and Y ₂ O ₃ . ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O ₃ are materials that have a melting point higher than the sintering temperature of lead zirconate titanate and can be dissolved in lead zirconate titanate. It is. Therefore, by using these materials for the metal oxide layer 5, when the laminate 2 is fired, the components of the metal oxide layer 5 are not easily precipitated at the grain boundaries of the piezoelectric body 3, and An increase in the number of grain boundaries per unit thickness in the body 3 is suppressed. Therefore, it is easy to suppress heat loss that occurs at the grain boundaries of the piezoelectric body 3 when a voltage (electric field) is applied between the internal electrodes 4A and 4B. As a result, it is possible to obtain a desired displacement with respect to the applied electric field when the multilayer piezoelectric element E1 is displaced. In addition, since the number of grain boundaries per unit thickness in the piezoelectric body 3 is reduced, it is possible to further suppress the occurrence of vertical cracks in the multilayer body 2.

(Second Embodiment)
Next, the configuration of the multilayer piezoelectric element E2 according to the second embodiment will be described with reference to FIGS. FIG. 6 is a perspective view showing the multilayer piezoelectric element according to the second embodiment. FIG. 7 is an enlarged longitudinal sectional view showing a part of the multilayer piezoelectric element according to the second embodiment. The multilayer piezoelectric element E2 according to the second embodiment is different from the multilayer piezoelectric element E1 according to the first embodiment described above in the arrangement of the metal oxide layer 5 in the multilayer body 2.

  The multilayer piezoelectric element E2 according to the second embodiment includes a multilayer body 2 including a piezoelectric body 3, internal electrodes 4A and 4B, and a metal oxide layer 5. The metal oxide layer 5 is formed in a layer between the internal electrodes 4 </ b> A and 4 </ b> B adjacent in the stacking direction of the stacked body 2 in the inactive portion Q of the stacked body 2. The metal oxide layer 5 is formed so as to slightly enter the active part P from the inactive part Q of the stacked body 2.

When manufacturing such a laminated piezoelectric element E2, as shown in FIG. 8, a plurality of green sheets 21 are formed, and electrode patterns 22A and 22B are formed on separate green sheets 21, respectively. Further, both end portions of the green sheet 21 different from the green sheet 21 on which the electrode pattern 22A or the electrode pattern 22B is formed (a portion including a region corresponding to the inactive portion Q and a part of a region corresponding to the active portion P). ) To form a ZrO ₂ paste layer 23.

After the electrode patterns 22A and 22B and the ZrO ₂ paste layer 23 are formed, the green sheet 21 on which the electrode pattern 22A is formed, the green sheet 21 on which the electrode pattern 22B is formed, and the green on which the ZrO ₂ paste layer 23 is formed The sheets 21 are stacked in a predetermined order. Further, the green sheet 21 on which the electrode patterns 22A and 22B and the ZrO ₂ paste layer 23 are not formed is laminated on the outermost layer as a protective layer. Thereby, the green laminated body 12 is formed.

  Then, the laminated body 2 is obtained by performing the press processing, cutting | disconnection, degreasing | defatting (debinding), and baking similar to 1st Embodiment. Then, the external electrodes 6A and 6B and the external electrodes 10A and 10B are provided on the side surfaces 2a and 2b of the multilayer body 2, and finally, a polarization process is performed to complete the multilayer piezoelectric element E2.

  As described above, also in the second embodiment, (1) generation of microcracks and vertical cracks can be reliably prevented, and (2) occurrence of unexpected cracks in the laminate 2 is reliably prevented. In addition, (3) the displacement of the stacked piezoelectric element E2 in the stacking direction can be suppressed.

(Third embodiment)
Next, the configuration of the multilayer piezoelectric element E3 according to the third embodiment will be described with reference to FIGS. FIG. 9 is a perspective view showing the multilayer piezoelectric element according to the third embodiment. FIG. 10 is an enlarged longitudinal sectional view showing a part of the multilayer piezoelectric element according to the third embodiment. The multilayer piezoelectric element E3 according to the third embodiment is different from the multilayer piezoelectric element E1 according to the first embodiment described above in the arrangement of the metal oxide layer 5 in the multilayer body 2.

  A multilayer piezoelectric element E3 according to the third embodiment includes a multilayer body 2 including a piezoelectric body 3, internal electrodes 4A and 4B, and a metal oxide layer 5. The metal oxide layer 5 includes a region 5a formed in the same layer as the internal electrodes 4A and 4B in the inactive portion Q of the multilayer body 2, and extends from the region 5a to the active portion P side to form the internal electrodes 4A and 4B. And a region 5b formed so as to overlap the entire upper surface. That is, the metal oxide layer 5 extends from the side surface 2a of the multilayer body 2 to the side surface 2b so as to be in contact with the internal electrodes 4A and 4B.

In order to form such a metal oxide layer 5, electrode patterns 22 A and 22 B are formed in a partial region of the upper surface of the green sheet 21, and ZrO ₂ paste is screen-printed to perform electrode printing on the upper surface of the green sheet 21. A ZrO ₂ paste layer 23 is formed on the printing region and the entire upper surface of the electrode patterns 22A and 22B. Then, similarly to the first embodiment, stacking, pressing, cutting, binder removal, and firing are sequentially performed.

  As described above, also in the third embodiment, (1) generation of microcracks and vertical cracks can be reliably prevented, and (2) occurrence of unexpected cracks in the laminate 2 is reliably prevented. In addition, (3) the displacement of the stacked piezoelectric element E3 in the stacking direction can be suppressed.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments. For example, the shape of the laminated body 2 is not limited to a polygonal column shape, and may be a cylindrical shape. In the stacked body 2, the side surfaces on which the external electrodes 6 </ b> A and 6 </ b> B and the external electrodes 10 </ b> A and 10 </ b> B are provided are not limited to the two side surfaces positioned to face each other, but may be two adjacent side surfaces. Further, when the laminate 2 has a cylindrical shape, the external electrodes 6A and 6B and the external electrodes 10A and 10B are disposed in arbitrary regions on the side surfaces as long as the external electrodes 6A and 10A and the external electrodes 6B and 10B are not in contact with each other. Can be provided.

  Further, the shape of the external electrodes 10A and 10B is not limited to the crank shape described above, but may be a sawtooth shape (zigzag shape) or a meandering shape as shown in FIGS. When the external electrodes 10A and 10B have a sawtooth shape (zigzag shape) and a meandering shape, the first portion 11a extends in a direction crossing the stacking direction.

  The internal electrode 4A may be exposed on the side surface 2b as long as it is electrically insulated from the external electrodes 6B and 10B provided on the side surface 2b. Similarly, the internal electrode 4B may be exposed to the side surface 2a as long as it is electrically insulated from the external electrodes 6A and 10A provided on the side surface 2a.

  In the above-described embodiment, the external electrode 6A has the electrode layer 7a and the electrode layer 8a, and the external electrode 6B has the electrode layer 7b and the electrode layer 8b, but the external electrode 6A is the electrode layer 7a. The external electrode 6B may be configured only by the electrode layer 7b.

  Further, in the above-described embodiment, the region 5b of the metal oxide layer 5 is configured to overlap the internal electrodes 4A and 4B. However, as illustrated in FIG. A configuration in which at least a part of the internal electrodes 4A and 4B overlap with each other may be employed.

1 is a perspective view showing a multilayer piezoelectric element according to a first embodiment. It is a longitudinal cross-sectional view which shows the lamination type piezoelectric element which concerns on 1st Embodiment. It is a longitudinal cross-sectional view which expands and shows a part of laminated piezoelectric element which concerns on 1st Embodiment. It is a figure for demonstrating the manufacturing method of the laminated piezoelectric element which concerns on 1st Embodiment. It is a disassembled perspective view for demonstrating the structure of the element body with which the multilayer piezoelectric element which concerns on 1st Embodiment is provided. It is a perspective view which shows the lamination type piezoelectric element which concerns on 2nd Embodiment. It is a longitudinal cross-sectional view which expands and shows a part of laminated piezoelectric element which concerns on 2nd Embodiment. It is a disassembled perspective view for demonstrating the structure of the element | base_body with which the multilayer piezoelectric element which concerns on 2nd Embodiment is provided. It is a longitudinal cross-sectional view which shows the lamination type piezoelectric element which concerns on 3rd Embodiment. It is a longitudinal cross-sectional view which expands and shows a part of laminated piezoelectric element which concerns on 3rd Embodiment. It is a perspective view which shows the lamination type piezoelectric element which concerns on 4th Embodiment. It is a perspective view which shows the lamination type piezoelectric element which concerns on 5th Embodiment. It is a longitudinal cross-sectional view which expands and shows a part of laminated piezoelectric element which concerns on 6th Embodiment.

Explanation of symbols

  E1 to E5 ... laminated piezoelectric element, 2 ... laminated body, 2a ... side surface (first side surface), 2b ... side surface (second side surface), 3 ... piezoelectric body, 4A ... internal electrode (first internal electrode), 4B ... Internal electrode (second internal electrode), 5 ... metal oxide layer, 5a ... region (first region), 5b ... region (second region), 6A ... external electrode (first external electrode), 6B ... external electrode ( Second external electrode), 10A, external electrode (third external electrode), 10B, external electrode (fourth external electrode), P, active part, Q, inactive part.

Claims (10)

A plurality of piezoelectric bodies and a plurality of internal electrodes including a first internal electrode and a second internal electrode are alternately stacked, and a first side surface and a second side extending in the stacking direction of the piezoelectric body and the internal electrodes. A laminate having side surfaces;
A metal oxide layer that is disposed in the laminated body and is made of a material having a melting point higher than the sintering temperature of the piezoelectric body;
A first external electrode disposed on the first side surface and electrically connected to the first internal electrode;
A second external electrode disposed on the second side surface and electrically connected to the second internal electrode;
A third external electrode connected to the first external electrode;
A fourth external electrode connected to the second external electrode,
The stacked body includes an active portion that is a portion where the first internal electrode and the second internal electrode overlap each other when viewed from the stacking direction, and the first internal electrode and the second internal electrode are stacked in the stacking direction. An inactive portion that is a portion that does not overlap when viewed from
The metal oxide layer includes a first region disposed in the inactive portion, and a second region disposed in the active portion extending from the first region to the active portion side,
The first external electrode has a connection surface that adheres to the first side surface and extends in the stacking direction;
The second external electrode has a connection surface that adheres to the second side surface and extends in the stacking direction;
The third external electrode and the fourth electrode are extendable in the stacking direction,
In the stacked body, the first region of the metal oxide layer is disposed so as to be the same layer as the layer in which the internal electrode is disposed, and overlaps at least a part of the internal electrode. The second region of the metal oxide layer is arranged as follows :
The first external electrode has a first electrode layer that is a metal strip and a second electrode layer formed of a resin material containing conductive particles,
The second external electrode has a first electrode layer that is a metal strip, and a second electrode layer formed of a resin material containing conductive particles,
The first electrode layer of the first external electrode is attached to the first side surface, and the second electrode layer of the first external electrode is connected to the third external electrode;
The stacked piezoelectric device, wherein the first electrode layer of the second external electrode is attached to the second side surface, and the second electrode layer of the second external electrode is connected to the fourth external electrode. element. A plurality of piezoelectric bodies and a plurality of internal electrodes including a first internal electrode and a second internal electrode are alternately stacked, and a first side surface and a second side extending in the stacking direction of the piezoelectric body and the internal electrodes. A laminate having side surfaces;
A metal oxide layer that is disposed in the laminated body and is made of a material having a melting point higher than the sintering temperature of the piezoelectric body;
A first external electrode disposed on the first side surface and electrically connected to the first internal electrode;
A second external electrode disposed on the second side surface and electrically connected to the second internal electrode;
A third external electrode connected to the first external electrode;
A fourth external electrode connected to the second external electrode,
The stacked body includes an active portion that is a portion where the first internal electrode and the second internal electrode overlap each other when viewed from the stacking direction, and the first internal electrode and the second internal electrode are stacked in the stacking direction. An inactive portion that is a portion that does not overlap when viewed from
The metal oxide layer includes a first region disposed in the inactive portion, and a second region disposed in the active portion extending from the first region to the active portion side,
The first external electrode has a connection surface that adheres to the first side surface and extends in the stacking direction;
The second external electrode has a connection surface that adheres to the second side surface and extends in the stacking direction;
The third external electrode and the fourth electrode are extendable in the stacking direction,
In the stacked body, the first region of the metal oxide layer is disposed so as to be the same layer as the layer where the internal electrode is disposed, and the first region of the metal oxide layer overlaps the entire internal electrode. The second region of the metal oxide layer is disposed ;
The first external electrode has a first electrode layer that is a metal strip and a second electrode layer formed of a resin material containing conductive particles,
The second external electrode has a first electrode layer that is a metal strip, and a second electrode layer formed of a resin material containing conductive particles,
The first electrode layer of the first external electrode is attached to the first side surface, and the second electrode layer of the first external electrode is connected to the third external electrode;
The stacked piezoelectric device, wherein the first electrode layer of the second external electrode is attached to the second side surface, and the second electrode layer of the second external electrode is connected to the fourth external electrode. element.   The multilayer piezoelectric element according to claim 1, wherein the first external electrode and the second external electrode layer are metal strips.   The multilayer piezoelectric element according to claim 1 or 2, wherein the third external electrode and the fourth external electrode have a flat plate shape. The third external electrode includes a first portion that is discontinuously arranged in the stacking direction, and a second portion that extends in a direction intersecting the stacking direction and connects the first portions.
The fourth external electrode includes a first portion discontinuously arranged in the stacking direction, and a second portion that extends in a direction intersecting the stacking direction and connects the first portions. The multilayer piezoelectric element according to claim 1 or 2. The third external electrode includes a first portion that is discontinuously arranged in the stacking direction, and a second portion that extends in a direction intersecting the stacking direction and connects the first portions.
The fourth external electrode has a first portion that is discontinuously arranged in the stacking direction, and a second portion that extends in a direction intersecting the stacking direction and connects the first portions.
The first external electrode is connected to the second portion of the third external electrode;
The second external electrode, the fourth has been laminated piezoelectric element according to claim 1 or 2, characterized in that it is connected to the second portion of the external electrode. The second electrode layer of the first external electrode is connected to the second portion of the third external electrode;
The multilayer piezoelectric element according to claim 6 , wherein the second electrode layer of the second external electrode is connected to the second portion of the fourth external electrode. Wherein the second portion of the second portion and the fourth external electrode of the third external electrode is any one of claims 5-7, characterized in that it does not overlap with the imaginary plane including the metal oxide layer The laminated piezoelectric element described in 1. The stacked type according to any one of claims 5 to 8 , wherein the first portion of the third external electrode and the first portion of the fourth external electrode extend in the stacking direction. Piezoelectric element. The piezoelectric body is formed of a piezoelectric material mainly composed of lead zirconate titanate,
The metal oxide _layer, ZrO _{2, MgO,} claim, characterized in that it is formed by a material containing at least one _{Nb 2 O 5, Ta 2 O} 5, CeO 2, Y 2 O 3 1~ 9 The multilayer piezoelectric element described in any one of the above.

Images