JP5018602B2 - Piezoelectric ceramic composition, and piezoelectric ceramic and laminated piezoelectric element using the same - Google Patents

Description

  The present invention relates to a piezoelectric ceramic composition, a piezoelectric ceramic using the same, and a laminated piezoelectric element.

Piezoelectric elements are used in a wide range of electronic components such as actuators, transformers, and ultrasonic motors. A piezoelectric ceramic composition used for a piezoelectric element is required to have a large piezoelectric characteristic, particularly a piezoelectric strain constant. Examples of the piezoelectric ceramic composition satisfying such characteristics include lead titanate (PbTiO ₃ ), lead zirconate (PbZrO ₃ ), and lead zinc niobate (Pb (Zn _1/3 Nb _2/3 ) O _3. ) And the like, and those composed of complex oxides in which elements of these complex oxides are partially substituted are known.

For example, in the composition formula of (Pb _1-xy Me _x Dy _y ) (Ti _1-z Ta _z ) O ₃ , Me is Ca, Ba or Sr, and 0.08 ≦ x ≦ 0.30, 0 A ferroelectric ceramic composition satisfying .01 ≦ y ≦ 0.15 and 0.01 ≦ z ≦ 0.15 is disclosed (see Patent Document 1).
JP 62-147604 A

  However, the conventional piezoelectric ceramic composition as described above needs to be fired at a high temperature in order to obtain high characteristics, and this firing is generally performed in an oxidizing atmosphere. Therefore, for example, in the production of a laminated piezoelectric element in which a piezoelectric ceramic composition and an internal electrode are fired simultaneously, a noble metal (Pt, Pt, which has a high melting point that can withstand high-temperature firing and is not oxidized even in an oxidizing atmosphere. Pd etc.) had to be used.

  However, since these internal electrode materials are extremely expensive, they have been a major factor that hinders the cost reduction of multilayer piezoelectric elements that are being applied to various electronic components in recent years. In order to reduce the price, it is desirable to replace the noble metal with relatively inexpensive Ag or the like. However, since Ag has a lower melting point than noble metal, the higher the content ratio of Ag, the lower the temperature at which it can be fired. There was a tendency that sufficient piezoelectric characteristics could not be obtained.

  Therefore, the present invention has been made in view of such circumstances, and provides a piezoelectric ceramic composition that can be sufficiently fired even when an internal electrode having a high Ag content is fired simultaneously. For the purpose. Another object of the present invention is to provide a piezoelectric ceramic using such a piezoelectric ceramic composition, and a laminated piezoelectric element including a piezoelectric layer made of the piezoelectric ceramic.

  As a result of intensive studies to achieve the above object, the present inventors have found that the main component of the lead titanate (PT) -lead zirconate (PZ) -zinc / lead niobate (PZN) system has a specific secondary It has been found that by blending the components at a predetermined content ratio, firing at a sufficiently low temperature becomes possible, and the present invention has been completed.

That is, the piezoelectric ceramic composition of the present invention contains a composite oxide represented by the following composition formula (1) as a main component, and as a subcomponent, exceeds 0 part by mass with respect to the composite oxide. With respect to an oxide or composite oxide of at least one element selected from the group consisting of Ta, Sb, Nb, W and Sn of not more than parts by mass, Dy, Gd, not less than 0 parts by mass and not more than 0.25 parts by mass At least one selected from the group consisting of Bi and V of more than 0 parts by mass and 0.15 parts by mass or less with respect to the oxide of at least one element selected from the group consisting of Yb, Er and Y, and the composite oxide. It is characterized by containing an oxide of one kind of element.
(Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (1)
[In the formula (1), Me is at least one element selected from the group consisting of Ca, Sr and Ba, and a, b, x, y and z are the following formulas (2), (3 ), (4), (5), (6), and (7).
0.96 ≦ a ≦ 1.03 (2)
0 ≦ b <0.1 (3)
0.005 ≦ x <0.05 (4)
0.42 ≦ y ≦ 0.46 (5)
0.50 ≦ z ≦ 0.53 (6)
x + y + z = 1 (7)]

  The piezoelectric ceramic composition of the present invention has at least one element selected from the group consisting of Ta, Sb, Nb, W, and Sn as subcomponents in the main component of the PT-PZ-PZN system, Dy, Gd, Since it contains at least one element selected from the group consisting of Yb, Er and Y, and at least one element selected from the group consisting of Bi and V, low-temperature firing, specifically, the inclusion of Ag Even if the firing is performed at a temperature at which the firing with the internal electrode can be performed at a ratio exceeding 85%, excellent piezoelectric characteristics can be obtained. Therefore, according to such a piezoelectric ceramic composition, a laminated piezoelectric element that is inexpensive and has sufficient piezoelectric characteristics can be obtained because the content ratio of Ag in the internal electrode is high.

The piezoelectric ceramic according to the present invention is preferably obtained by firing the piezoelectric ceramic composition according to the present invention. The piezoelectric ceramic according to the present invention includes a composite oxide represented by the following composition formula (1) as a main component. As a component, with respect to the composite oxide, at least one element selected from the group consisting of Ta, Sb, Nb, W, and Sn exceeding 0 parts by mass and 0.6 parts by mass or less in terms of oxide, the composite oxide On the other hand, it is 0 in terms of oxide with respect to at least one element selected from the group consisting of Dy, Gd, Yb, Er and Y exceeding 0 parts by mass and less than 0.25 parts by mass in terms of oxide, and composite oxide. It contains at least one element selected from the group consisting of Bi and V exceeding 0.15 parts by mass and less than 0.15 parts by mass, and an oxide of Ag.
(Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (1)
[In the formula (1), Me is at least one element selected from the group consisting of Ca, Sr and Ba, and a, b, x, y and z are the following formulas (2), (3 ), (4), (5), (6), and (7).
0.96 ≦ a ≦ 1.03 (2)
0 ≦ b <0.1 (3)
0.005 ≦ x <0.05 (4)
0.42 ≦ y ≦ 0.46 (5)
0.50 ≦ z ≦ 0.53 (6)
x + y + z = 1 (7)]

  Such a piezoelectric ceramic has the same composition as the above piezoelectric ceramic composition and further contains an Ag oxide, so that simultaneous firing with an internal electrode such that the Ag content ratio exceeds 85% is possible. Even those formed by low-temperature firing can exhibit excellent piezoelectric properties.

  Furthermore, the present invention provides a multilayer piezoelectric element comprising a piezoelectric layer comprising the piezoelectric ceramic of the present invention and an electrode (internal electrode) layer having an Ag content of 85% by mass or more. Such a multilayer piezoelectric element of the present invention is inexpensive because the Ag content is 85% by mass, and even if formed by co-firing with such an electrode layer, the piezoelectric ceramic of the present invention described above is used. Since the piezoelectric layer is provided, excellent piezoelectric characteristics can be exhibited.

  According to the present invention, it is possible to provide a piezoelectric ceramic composition that can be sufficiently fired even when an internal electrode having a high Ag content is fired simultaneously. In addition, according to the present invention, it is possible to provide a piezoelectric ceramic using such a piezoelectric ceramic composition and a multilayer piezoelectric element including a piezoelectric layer composed of such a piezoelectric ceramic.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as necessary.

  FIG. 1 is a diagram schematically showing a cross-sectional configuration of a multilayer piezoelectric element according to a preferred embodiment. As shown in FIG. 1, the multilayer piezoelectric element 10 is a multilayer in which the internal electrodes 1 a and the internal electrodes 1 b are alternately arranged, and the piezoelectric layer 2 is sandwiched between the internal electrodes 1 a and 1 b. It has a structure. In addition, a protective layer 3a and a protective layer 3b are provided in the outermost layer of this laminated structure. Furthermore, a pair of external electrodes 4 are provided on both end faces along the stacking direction of the stacked structure. The internal electrode 1a and the internal electrode 1b are connected to the external electrodes 4 on different sides.

  In the multilayer piezoelectric element 10 having such a configuration, the thickness of the piezoelectric layer 2 is preferably 1 to 200 μm, more preferably 20 to 150 μm, and further preferably 50 to 100 μm. Moreover, the thickness of the internal electrode 1a and the internal electrode 1b is preferably 0.5 to 20 μm, and more preferably 1.0 to 10 μm.

  The internal electrodes 1a and 1b are not particularly limited as long as they are made of a material used as an internal electrode of the multilayer piezoelectric element, and are composed of, for example, Ag, Pd, Pt metal alone, an alloy containing Ag, or the like. In particular, in the multilayer piezoelectric element 10 of the present embodiment, the internal electrodes 1a and 1b are preferably made of a material containing 85% by mass or more of Ag. Specifically, an alloy containing 85% by mass or more of Ag (for example, , Ag—Pd alloy, Ag—Pt alloy, etc.), or those consisting of Ag alone are preferable. The laminated piezoelectric element 10 of the present embodiment is a material of the internal electrodes 1a and 1b having such a high Ag ratio because the piezoelectric layer 2 is formed from a piezoelectric ceramic composition as described later. Can be fired simultaneously.

  On the other hand, the piezoelectric layer 2 is composed of a piezoelectric ceramic obtained by firing a piezoelectric ceramic composition having a specific composition. Hereinafter, a piezoelectric ceramic composition suitable as a constituent material of the piezoelectric layer 2 will be described.

The piezoelectric ceramic composition of the present embodiment includes a composite oxide represented by the following composition formula (1) as a main component, and as a subcomponent, more than 0 parts by mass and 0.6 mass with respect to the composite oxide. More than 0 parts by mass with respect to oxides of at least one element selected from the group consisting of Ta, Sb, Nb, W and Sn (hereinafter referred to as “first subcomponent”) and composite oxides 0.25 parts by mass or less of an oxide of at least one element selected from the group consisting of Dy, Gd, Yb, Er and Y (hereinafter referred to as “second subcomponent”), and the composite oxide , And an oxide of at least one element selected from the group consisting of Bi and V exceeding 0 parts by mass and 0.15 parts by mass or less (hereinafter referred to as “third subcomponent”).
(Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (1)
[In the formula (1), Me is at least one element selected from the group consisting of Ca, Sr and Ba, and a, b, x, y and z are the following formulas (2), (3 ), (4), (5), (6), and (7).
0.96 ≦ a ≦ 1.03 (2)
0 ≦ b <0.1 (3)
0.005 ≦ x <0.05 (4)
0.42 ≦ y ≦ 0.53 (5)
0.45 ≦ z ≦ 0.56 (6)
x + y + z = 1 (7)]

  The composite oxide as the main component has a so-called perovskite structure. Pb and Me in the composite oxide represented by the above formula (1) are located at the A site of the perovskite structure. On the other hand, Zn, Nb, Ti, and Zr are located at the B site of the perovskite structure. In the piezoelectric ceramic composition of the present embodiment, the composite oxide represented by the above formula (1) is preferably contained in an amount of 95% by mass or more, and 98.0 to 99.9% by mass in the total amount of the composition. More preferably. When the composite oxide is contained at such a ratio, sufficient piezoelectric characteristics (particularly piezoelectric strain constant) can be obtained.

  “A” indicating the ratio of the A-site element in the composite oxide represented by the above formula (1) is preferably 0.96 ≦ a ≦ 1.03. When the ratio a of the A-site element is less than 0.96 or exceeds 1.03, the piezoelectric strain constant decreases. From the viewpoint of obtaining a good piezoelectric strain constant, the A-site element ratio a is preferably 0.97 ≦ a ≦ 1.02, and more preferably 0.98 ≦ a ≦ 1.01.

  In the composite oxide represented by the above formula (1), a part of Pb that is an A site element may be substituted by an element represented by Me (Ca, Sr, Ba). Such substitution may further improve the piezoelectric strain constant. However, if the amount of substitution is too large, the piezoelectric strain constant tends to decrease rather. Therefore, the substitution amount b with Me is 0.1 or less, more preferably 0.005 ≦ b ≦ 0.08, and further preferably 0.007 ≦ b ≦ 0.05. Note that the substitution element represented by Me may be a plurality of types of Ca, Sr, and Ba. In this case, it is preferable that the total substitution amount of each element satisfies the value b described above.

  Among the B site elements in the complex oxide represented by the above formula (1), x representing the ratio of Zn and Nb is 0.005 ≦ x <0.05. This x affects the firing temperature. If this value is less than 0.005, the firing temperature cannot be lowered sufficiently. On the other hand, if it exceeds 0.05, the crystal grain size becomes small, and as a result, the piezoelectric strain constant decreases. From the viewpoint of obtaining sufficient sinterability at a low firing temperature, the ratio x of Zn and Nb is preferably 0.01 ≦ x ≦ 0.04, and more preferably 0.02 ≦ x ≦ 0.04. preferable.

  Further, among the B-site elements, y, which is the ratio of Ti, and z, which is the ratio of Zr, are in the following ranges from the viewpoint of obtaining a good piezoelectric strain constant. That is, the ratio y of Ti is 0.42 ≦ y ≦ 0.53. The ratio z of Zr is 0.45 ≦ z ≦ 0.56. By setting the proportions of Ti and Zr within these ranges, a large piezoelectric strain constant can be obtained in the vicinity of the morphotropic phase boundary (MPB). In order to obtain such an effect even better, the Ti ratio y is preferably 0.42 ≦ y ≦ 0.50, and more preferably 0.42 ≦ y ≦ 0.46. On the other hand, the ratio z of Zr is more preferably 0.48 ≦ z ≦ 0.53, and further preferably 0.50 ≦ z ≦ 0.53.

  The above is the preferred composition of the complex oxide as the main component in the dielectric ceramic composition of the present embodiment. The dielectric ceramic composition contains the above-described first, second, and third subcomponents in addition to the complex oxide.

The first subcomponent is an oxide of at least one element selected from the group consisting of Ta, Sb, Nb, W, and Sn. Specific examples of these oxides include Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ , WO ₃ and SnO ₂ . The first subcomponent is contained in an amount exceeding 0 parts by mass and 0.6 parts by mass or less with respect to 100 parts by mass of the composite oxide as the main component. By including the first subcomponent at such a ratio, the microstructure of the sintered body is appropriately controlled, and the piezoelectric characteristics can be improved. From the viewpoint of obtaining such an effect satisfactorily, the content of the first subcomponent is preferably 0.05 to 0.4 parts by mass, and preferably 0.2 to 0.4 parts by mass with respect to the main component. And more preferred.

The second subcomponent is an oxide of at least one element selected from the group consisting of Dy, Gd, Yb, Er, and Y. Specific examples of these oxides include Dy ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , Er ₂ O ₃ , and Y ₂ O ₃ . The second subcomponent is contained in an amount exceeding 0 parts by mass and 0.25 parts by mass or less with respect to 100 parts by mass of the composite oxide as the main component. By including the second subcomponent at such a ratio, the crystal grains of the obtained sintered body are favorably grown, and the effect of improving the piezoelectric characteristics can be obtained. From the viewpoint of obtaining such an effect satisfactorily, the content of the second subcomponent is preferably 0.05 to 0.25 parts by mass, and 0.10 to 0.25 parts by mass with respect to the main component. And more preferred.

Furthermore, the third subcomponent is an oxide of at least one element selected from the group consisting of Bi and V. Examples of these oxides include Bi ₂ O ₃ and V ₂ O ₅ . The third subcomponent is contained in an amount exceeding 0 parts by mass and 0.15 parts by mass or less with respect to 100 parts by mass of the composite oxide as the main component. By including the third subcomponent in such a ratio, the firing temperature can be lowered, and a dense sintered body can be obtained even at a low temperature, and as a result, high piezoelectric characteristics can be obtained. From the viewpoint of obtaining such effects well, the content of the third subcomponent is preferably 0.025 to 0.15 parts by mass, and 0.05 to 0.15 parts by mass with respect to the main component. And more preferred.

  Note that the first to third subcomponents may include a plurality of types of oxides of elements corresponding to the subcomponents. In this case, in each subcomponent, the total content of the plurality of types of oxides is in the above-described range.

  In addition to the composite oxide represented by the above (1) that is the main component and the first to third subcomponents, the dielectric ceramic composition of the present embodiment includes other components within a range that does not impair the effects of the present invention. May further be included. Examples of other components include elements such as Hf, Cr, Mo, Tb, Ho, and Tm, and oxides thereof.

  The piezoelectric ceramic constituting the piezoelectric layer 2 is obtained by firing the above-described piezoelectric ceramic composition. And since the ratio of a structural element hardly changes in baking of a piezoelectric ceramic composition, a piezoelectric ceramic comes to have a composition similar to a piezoelectric ceramic composition. However, as described above, when the material of the internal electrodes 1a and 1b includes a single Ag or an alloy containing Ag, particularly when a material having a content ratio of Ag exceeding 85% by mass is used, the Ag May move from the internal electrode to the piezoelectric layer 2. Therefore, the piezoelectric ceramic according to this embodiment further contains an Ag oxide in addition to the constituent elements of the piezoelectric ceramic composition.

That is, the piezoelectric ceramic of the present embodiment includes a composite oxide represented by the following composition formula (1) as a main component, and exceeds 0 part by mass in terms of oxide with respect to the composite oxide as a subcomponent. With respect to at least one element selected from the group consisting of Ta, Sb, Nb, W and Sn of 0.6 parts by mass or less, with respect to the composite oxide, it exceeds 0 parts by mass and is 0.25 parts by mass or less in terms of oxide. With respect to at least one element selected from the group consisting of Dy, Gd, Yb, Er, and Y, and a composite oxide, from the group consisting of Bi and V exceeding 0 to 0.15 parts by mass in terms of oxide It contains at least one element selected and an oxide of Ag.
(Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (1)
[In the formula (1), Me is at least one element selected from the group consisting of Ca, Sr and Ba, and a, b, x, y and z are the following formulas (2), (3 ), (4), (5), (6), and (7).
0.96 ≦ a ≦ 1.03 (2)
0 ≦ b <0.1 (3)
0.005 ≦ x <0.05 (4)
0.42 ≦ y ≦ 0.53 (5)
0.45 ≦ z ≦ 0.56 (6)
x + y + z = 1 (7)]

  The content of Ag oxide in the piezoelectric ceramic is preferably 0.01 to 0.5% by mass and more preferably 0.05 to 0.30% by mass with respect to the composite oxide. When Ag oxide is not included in the piezoelectric ceramic, or when the content exceeds the above range, the piezoelectric strain constant tends to decrease.

  The piezoelectric ceramic according to the present embodiment includes Ag oxide as described above, so that even if it is fired at a low temperature, further excellent piezoelectric characteristics (particularly high piezoelectric strain constant) can be obtained. In some cases, the movement of Ag as described above may not occur depending on the firing conditions. In this case, in order to obtain the piezoelectric ceramic according to the present embodiment, the amount of Ag oxide corresponding to the above is obtained in the piezoelectric ceramic composition. What is necessary is just to add.

  In addition, although each element of the subcomponent contained in a piezoelectric ceramic is mainly contained by the form of an oxide as mentioned above, respectively, it is not necessarily limited to the form of an oxide.

  Next, a method for manufacturing the multilayer piezoelectric element 10 having the above-described configuration will be described.

First, a starting material of a complex oxide that is a main component of a piezoelectric ceramic composition for obtaining the piezoelectric layer 2 is prepared and weighed so as to obtain a complex oxide having a desired composition. Examples of the starting material include oxides of each constituent element of the composite oxide and powders such as carbonates or oxalates that can be changed to these oxides by firing. Specific examples of the oxide include PbO, TiO ₂ , ZrO ₂ , ZnO, Nb ₂ O ₅ , SrO, BaO, and CaO. As the starting material powder, those having an average particle size of about 0.5 to 10 μm are preferable.

Moreover, in addition to the starting material of such a main component, the starting materials of the first to third and other subcomponents described above are prepared. The starting materials for the first to third subcomponents are preferably oxides of the respective elements as described above. Furthermore, when adding Ag oxide in the stage of a piezoelectric ceramic composition, Ag oxide (for example, Ag ₂ O) is also prepared.

  Subsequently, the starting materials of the main component and the subcomponent are mixed, and if necessary, wet pulverization and mixing are performed to obtain a raw material mixture. Such wet grinding and mixing can be performed using, for example, a ball mill. In addition, you may make it add the starting material of a subcomponent after the temporary baking mentioned later. Further, only some of the subcomponents may be added to the raw material mixture, and the rest may be added after the pre-baking. However, from the viewpoint of forming the homogeneous piezoelectric layer 2, it is more preferable to add a subcomponent before calcination.

  Then, this raw material mixture is dried, and calcined, for example, by performing a heat treatment at a temperature of 750 to 950 ° C. for 1 to 6 hours. This pre-baking may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. The obtained calcined product is wet-ground and mixed by a ball mill or the like to obtain a calcined powder containing a main component and, if necessary, a subcomponent. By such preliminary calcination, a composite oxide is formed from the starting material of the main component, and a piezoelectric ceramic composition containing the main component of the composite oxide and subcomponents is obtained.

  Next, an organic binder, an organic solvent, an organic plasticizer, and the like are added to the piezoelectric ceramic composition thus obtained, and the mixture is mixed for about 20 hours by a ball mill or the like to obtain a piezoelectric paste.

  In addition to such a piezoelectric paste, an electrode paste for forming the internal electrodes 1a and 1b is prepared. The electrode paste is obtained, for example, by adding a binder, an organic solvent or the like to the powder of the constituent material (metal or the like) of the internal electrodes 1a and 1b as described above. The metal content in the electrode paste is preferably 40% by mass or more, and more preferably 50 to 60% by mass. If the metal content is less than 40% by mass, the resulting internal electrodes 1a and 1b may have insufficient conductivity.

  Then, the piezoelectric paste is applied onto a base film made of polyethylene terephthalate (PET) or the like by, for example, a doctor blade method to obtain a piezoelectric green sheet for forming the piezoelectric layer 2. Next, an electrode paste is applied on the piezoelectric green sheet by a screen printing method or the like to obtain a laminated sheet in which an electrode paste layer is formed on the piezoelectric green sheet. At this time, the electrode paste layer is formed corresponding to the shape of the internal electrodes 1a and 1b.

  Thereafter, a plurality of the obtained laminated sheets are stacked so that the electrode paste layers and the piezoelectric green sheets are alternately arranged, and the piezoelectric layers to be the protective layers 3a and 3b are formed above and below the laminated structure thus obtained. Stack green sheets further to get green chips. The green chip manufacturing method is not necessarily limited to this, and the piezoelectric paste and the electrode paste may be alternately and repeatedly applied.

  The green chip thus obtained is subjected to predetermined heating to remove the binder and the organic solvent contained in the middle of each pace. The binder removal is preferably performed under conditions that do not allow firing of the piezoelectric ceramic composition in the piezoelectric paste. For example, it can be performed under conditions of 300 to 650 ° C. and about 0.5 to 50 hours.

  Thereafter, the green chip after debinding is subjected to a firing process (main firing) in, for example, a sealed container. In this main firing treatment, the piezoelectric green sheet (piezoelectric ceramic composition in the piezoelectric green sheet) and the electrode paste layer are fired at the same time, and the piezoelectric layer 2 comprising the piezoelectric ceramic from the piezoelectric green sheet is transferred from the electrode paste layer to the internal electrode 1a, 1b is formed. Further, the protective layers 3a and 3b are formed from a piezoelectric green sheet laminated on the outermost layer of the green chip.

  The firing temperature in the main firing is preferably 900 to 1050 ° C, more preferably 900 to 1000 ° C, and still more preferably 910 to 970 ° C. Since the piezoelectric ceramic composition contained in the piezoelectric green sheet has the specific composition as described above, it is sufficiently lower even at a firing temperature at which Ag can be simultaneously fired. Sintering results in excellent piezoelectric properties (particularly high piezoelectric strain constant).

  Then, two end faces (end faces where the internal electrodes 1a and 1b are exposed) in the stacking direction in the fired laminate are subjected to a polishing treatment such as barrel polishing or sand blasting as necessary, and then the external electrode 4 Bake each. Specifically, an external electrode paste including a metal and an organic binder constituting the external electrode 4 is applied to the end face of the laminate, and then fired. In addition, you may form the external electrode 4 by methods, such as sputtering, vapor deposition, and electroless plating, besides baking. In this way, the multilayer piezoelectric element 10 having the structure shown in FIG. 1 is obtained.

  The piezoelectric ceramic composition, the piezoelectric ceramic, and the laminated piezoelectric element according to the preferred embodiments of the present invention have been described above, but the present invention is not necessarily limited to these embodiments, and does not depart from the spirit of the present invention. You may change suitably.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

[Example A; Evaluation of influence of second and third subcomponents]
(Examples 1-1 to 1-23, Comparative Examples 1-1 to 1-18)
First, the start of the composite oxide represented by (Pb _0.965 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.04 Ti _0.455 Zr _0.505 ] O ₃ which is the main component. Raw materials were prepared. That is, PbO powder, SrCO ₃ powder, ZnO powder, Nb ₂ O ₅ powder, TiO ₂ powder, and ZrO ₂ powder were prepared as the main component raw materials, and these were weighed so as to have the above composition.

Moreover, Ta ₂ O ₅ powder (first subcomponent), Dy ₂ O ₃ powder (second subcomponent), Bi ₂ O ₃ powder (third subcomponent), and Ag ₂ are used as starting materials for the subcomponents. O powders were prepared and added to the main starting material to obtain a raw material composition. At this time, the amount of Ta ₂ O ₅ powder is 0.2 wt% with respect to the main component, and the amount of Ag ₂ O powder is 0.1 wt% with respect to the main component, Various raw material compositions were prepared by changing the amounts of Dy ₂ O ₃ powder and Bi ₂ O ₃ powder so as to be the amounts shown in Table 1 below with respect to the main component.

  Next, each raw material composition was wet-mixed for 16 hours using a ball mill and then calcined at 700 to 900 ° C. for 2 hours in the air. The obtained calcined product was finely pulverized and then wet pulverized for 16 hours using a ball mill to obtain various calcined powders (piezoelectric ceramic compositions) obtained from the respective raw material compositions. After drying this, an acrylic resin was added as a binder and granulated to obtain a disk-shaped molded body having a diameter of 17 mm and a thickness of 1 mm at a pressure of about 445 MPa using a uniaxial press molding machine.

  After molding, the resulting molded body was heat treated to remove the binder, and then subjected to heat treatment at 930 ° C. for 2 hours to perform main firing. Then, an Ag paste containing Ag powder is printed on both sides of the obtained sintered body and baked at 350 ° C., and an electric field of 3 kV / mm is applied for 15 minutes in silicone oil at 120 ° C. to perform polarization treatment. It was. As a result, a sample for measuring the piezoelectric constant d33 obtained using each raw material composition was obtained.

And about each sample produced in this way, the piezoelectric-strain constant d33 was measured by the resonance-antiresonance method using d33 meter (d33 meter by Chinese Academy of Sciences voice research laboratory; MODEL ZJ-3D). Table 1 shows the results obtained using each sample.

From Table 1, the sample of the example in which Dy ₂ O ₃ and Bi ₂ O ₃ were added as subcomponents has an excellent piezoelectric strain constant compared to the sample of the comparative example in which one or both of these were not added. It was confirmed.

[Example B; Evaluation of influence of Ag oxide]
(Examples 2-1 to 2-4, Comparative examples 2-1 to 2-2)
The amount of Dy ₂ O ₃ , which is a subcomponent in the piezoelectric ceramic composition, is fixed to 0.075 wt%, the amount of Bi ₂ O ₃ is fixed to 0.100 wt%, and the amount of Ag ₂ O shown in Table 2 is Except that they were added, various samples for measuring the piezoelectric constant d33 were prepared in the same manner as in Example A, and these d33 were measured in the same manner. The obtained results are shown in Table 2.

From Table 2, it was confirmed that the sample of the Example containing Ag ₂ O as a subcomponent can obtain an excellent piezoelectric strain constant as compared with the sample not containing Ag ₂ O.

[Example C; Evaluation of the effect of the first subcomponent]
(Examples 3-1 to 3-13, Comparative examples 3-1 to 3-2)
In the piezoelectric ceramic composition, the amount of Ta ₂ O ₅ as the first subcomponent is changed as shown in Table 3, or in place of Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ , WO ₃ and Samples for measuring various piezoelectric constants d33 were prepared in the same manner as in Example A except that SnO ₂ was used in the types and amounts shown in Table 3, and these d33 were measured in the same manner. The obtained results are shown in Table 3.

As shown in Table 3, first, a sample of an example in which Ta ₂ O _{5 as} the first subcomponent is included in the scope of the present invention does not include Ta ₂ O ₅ (Comparative Example 3-1). In addition, it was confirmed that an excellent piezoelectric strain constant was obtained as compared with the case where the amount of Ta ₂ O ₅ was outside the range of the present invention (Comparative Example 3-2). Further, as the first subcomponent, _Ta 2 _{O 5} in _{place, Sb 2 O 3, Nb 2} O 5, WO 3 and also with SnO _2, similarly high piezoelectric strain constant in the case of _Ta 2 _{O 5} Was found to be obtained.

[Example D: Evaluation of influence of main component composition]
(Examples 4-1 to 4-4, Comparative examples 4-1 to 4-2)
In the piezoelectric ceramic composition, the composition of the main component represented by (Pb _ab Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ is the composition shown in Table 4. As an auxiliary component, the amount of Ta ₂ O ₅ was 0.2 wt%, the amount of Dy ₂ O ₃ was 0.075 wt%, and the amount of Bi ₂ O ₃ was 0.100 wt%. Except that, various samples for measuring the piezoelectric constant d33 were prepared in the same manner as in Example A, and these d33 were measured in the same manner. Table 4 shows the obtained results.

  From Table 4, the sample of the example in which the ratio a of the A-site element of the composite oxide as the main component was within the scope of the present invention was the sample of the comparative example in which the ratio a was outside the scope of the present invention. It was confirmed that a higher piezoelectric strain constant was obtained than

(Examples 5-1 to 5-6, Comparative Example 5-1)
In the piezoelectric ceramic composition, the composition of the main component represented by (Pb _a−b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ becomes the composition shown in Table 5. As an auxiliary component, the amount of Ta ₂ O ₅ was 0.2 wt%, the amount of Dy ₂ O ₃ was 0.075 wt%, and the amount of Bi ₂ O ₃ was 0.100 wt%. Except that, various samples for measuring the piezoelectric constant d33 were prepared in the same manner as in Example A, and these d33 were measured in the same manner. The results obtained are shown in Table 5.

  From Table 5, the sample of the example in which the substitution amount b of Pb, which is an A-site element, was within the scope of the present invention was compared with the substitution amount b outside the scope of the present invention. It was confirmed that a high piezoelectric strain constant was obtained compared to the sample of the example.

(Examples 6-1 to 6-13, Comparative Examples 6-1 to 6-10)
In the piezoelectric ceramic composition, the composition of the main component represented by (Pb _a−b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ becomes the composition shown in Table 6. As an auxiliary component, the amount of Ta ₂ O ₅ was 0.2 wt%, the amount of Dy ₂ O ₃ was 0.075 wt%, and the amount of Bi ₂ O ₃ was 0.100 wt%. Except that, various samples for measuring the piezoelectric constant d33 were prepared in the same manner as in Example A, and these d33 were measured in the same manner. The results obtained are shown in Table 6.

  From Table 6, the sample of the example in which the ratio x of Zn and Nb as the B site element, the ratio y of Ti, and the ratio z of Zr were within the scope of the present invention, these ratios are outside the scope of the present invention. It was confirmed that a high piezoelectric strain constant was obtained as compared with the comparative sample.

(Examples 7-1 to 7-3)
In the piezoelectric ceramic composition, the composition of the main component represented by (Pb _ab Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ is the composition shown in Table 7. As an auxiliary component, the amount of Ta ₂ O ₅ was 0.2 wt%, the amount of Dy ₂ O ₃ was 0.075 wt%, and the amount of Bi ₂ O ₃ was 0.100 wt%. Except that, various samples for measuring the piezoelectric constant d33 were prepared in the same manner as in Example A, and these d33 were measured in the same manner. The results obtained are shown in Table 7.

  From Table 7, it was confirmed that when Ca, Sr and Ba were used as Me, which is the A site element of the composite oxide as the main component, a high piezoelectric strain constant was obtained.

[Example E; Evaluation of influence of second and third subcomponents]
(Examples 8-1 to 8-24, Comparative Examples 8-1 to 8-12)
In the piezoelectric ceramic composition, various samples for measuring the piezoelectric constant d33 were prepared in the same manner as in Example A except that the types and amounts of the second and third subcomponents were changed as shown in Table 8. It produced and measured these d33 similarly. Table 8 shows the obtained results.

  As shown in Table 8, the samples of the examples in which the amounts of the second and third subcomponents were within the scope of the present invention were compared to the samples of the comparative examples in which they were outside the scope of the present invention. It has been found that a high piezoelectric strain constant can be obtained. Moreover, it was confirmed that the same effect can be obtained even if the types of the second and third subcomponents are changed.

It is a figure which shows typically the cross-sectional structure of the laminated piezoelectric element which concerns on suitable embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a, 1b ... Internal electrode, 2 ... Piezoelectric layer, 3a, 3b ... Protective layer, 4 ... External electrode, 10 ... Multilayer type piezoelectric element.

Claims (3)

A composite oxide represented by the following composition formula (1) as a main component;
As a minor component
With respect to the composite oxide, an oxide of at least one element selected from the group consisting of Ta, Sb, Nb, W, and Sn exceeding 0 part by mass and 0.6 parts by mass or less,
With respect to the composite oxide, an oxide of at least one element selected from the group consisting of Dy, Gd, Yb, Er, and Y exceeding 0 part by mass and not more than 0.25 part by mass; and
The composite oxide contains an oxide of at least one element selected from the group consisting of Bi and V exceeding 0 parts by mass and 0.15 parts by mass or less.
A piezoelectric ceramic composition characterized by that.
[Pb _a-b Me _b ] [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (1)
[In the formula (1), Me is at least one element selected from the group consisting of Ca, Sr and Ba, and a, b, x, y and z are the following formulas (2), (3 ), (4), (5), (6), and (7).
0.96 ≦ a ≦ 1.03 (2)
0 ≦ b <0.1 (3)
0.005 ≦ x <0.05 (4)
0.42 ≦ y ≦ 0.46 (5)
0.50 ≦ z ≦ 0.53 (6)
x + y + z = 1 (7)] A composite oxide represented by the following composition formula (1) as a main component;
As a minor component
With respect to the composite oxide, at least one element selected from the group consisting of Ta, Sb, Nb, W and Sn exceeding 0 parts by mass and 0.6 parts by mass or less in terms of oxides,
With respect to the composite oxide, at least one element selected from the group consisting of Dy, Gd, Yb, Er, and Y in excess of 0 part by mass and 0.25 part by mass or less in terms of oxide,
With respect to the composite oxide, at least one element selected from the group consisting of Bi and V exceeding 0 parts by mass and 0.15 parts by mass or less in terms of oxides, and
Containing an oxide of Ag,
A piezoelectric ceramic characterized by that.
(Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (1)
[In the formula (1), Me is at least one element selected from the group consisting of Ca, Sr and Ba, and a, b, x, y and z are the following formulas (2), (3 ), (4), (5), (6), and (7).
0.96 ≦ a ≦ 1.03 (2)
0 ≦ b <0.1 (3)
0.005 ≦ x <0.05 (4)
0.42 ≦ y ≦ 0.46 (5)
0.50 ≦ z ≦ 0.53 (6)
x + y + z = 1 (7)] A piezoelectric layer comprising the piezoelectric ceramic according to claim 2;
An electrode layer having an Ag content of 85% by mass or more;
A multilayer piezoelectric element comprising:

Images