JP3923064B2 - Multilayer piezoelectric element and method for manufacturing the same - Google Patents

Description

  The present invention relates to a laminated piezoelectric element used as an actuator, a piezoelectric buzzer, a sounding body, a sensor, and the like, and further relates to a manufacturing method thereof.

  For example, an actuator that uses displacement generated by the piezoelectric effect as a mechanical drive source has advantages such as low power consumption and heat generation, good response, and miniaturization and weight reduction. However, it has come to be used in a wide range of fields.

By the way, a piezoelectric ceramic composition used for this type of actuator is required to have a large piezoelectric characteristic, particularly a piezoelectric strain constant. As a piezoelectric ceramic composition satisfying this, for example, lead titanate (PbTiO ₃ ) and zirconic acid are used. A ternary piezoelectric ceramic composition composed of lead (PbZrO ₃ ) and zinc / lead niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ], and the ternary piezoelectric ceramic composition Have been developed in which a part of Pb is substituted with Sr, Ba, Ca, or the like.

  However, these conventional piezoelectric ceramic compositions need to be fired at a relatively high temperature, and since firing is performed in an oxidizing atmosphere, for example, in a laminated actuator that simultaneously fires internal electrodes, a high melting point is obtained. It is necessary to use a noble metal (for example, Pt, Pd, etc.) that does not oxidize even when fired in an oxidizing atmosphere. As a result, the cost is increased and the cost of the manufactured piezoelectric element is hindered.

  From such a situation, the applicant of the present application includes, in the ternary piezoelectric ceramic composition, a first subcomponent including at least one selected from Fe, Co, Ni, and Cu, and Sb, Nb, and Ta. It has been proposed that low temperature firing is possible by adding a second subcomponent including at least one selected, and that an inexpensive material such as an Ag—Pd alloy can be used for the internal electrode (see Patent Document 1). ).

The invention described in Patent Document 1 includes the ternary piezoelectric ceramic composition and the piezoelectric ceramic composition in which part of Pb is replaced with Sr, Ba, Ca, etc. in the ternary piezoelectric ceramic composition. By adding a first subcomponent including at least one selected from Co, Ni, and Cu and a second subcomponent including at least one selected from Sb, Nb, and Ta, a high piezoelectric strain constant is obtained. Provided is a piezoelectric ceramic composition that is densified without impairing various piezoelectric characteristics even when fired at a low temperature and has increased mechanical strength, and has a piezoelectric layer composed of the piezoelectric ceramic composition. That's it.
JP 2004-137106 A

  However, when using a cheaper metal (Cu) as an electrode material, the firing in an oxidizing atmosphere (for example, in air) has the disadvantage that the electrode material is oxidized even when fired at a low temperature and the conductivity is impaired. appear.

In order to eliminate the inconvenience as described above, it is necessary to perform firing in a reducing atmosphere having a low oxygen partial pressure (the oxygen partial pressure is about 1 × 10 ⁻⁹ to 1 × 10 ⁻⁶ atm). However, when fired in a reducing atmosphere, the obtained fired body contains more oxygen vacancies than a sintered body fired in air, and therefore has an insulation resistance particularly at high temperatures (100 ° C. or higher). This leads to a decrease in the high temperature load life (insulation life) of the product. The temperature range of 100 ° C. to 200 ° C. is often the standard operating temperature of a product, and a decrease in insulation resistance in this temperature range is a serious problem because it significantly impairs the reliability of the product.

  The present invention has been proposed in view of such a conventional situation, and even when Cu is used for the internal electrode layer, it is possible to improve the decrease in insulation resistance at high temperature and to be excellent in reliability. Another object of the present invention is to provide a laminated piezoelectric element, and further to provide a manufacturing method thereof.

  In order to achieve the above object, the present inventors have made various studies over a long period of time. As a result, the inventors have found that the presence of Cu in some form in the piezoelectric layer improves the reduction in electrical resistance at high temperatures.

The present invention has been devised based on the examination results. That is, the multilayer piezoelectric element of the present invention has (Pb _ab Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (where 0.96 ≦ a ≦ 1.03 0 <b ≦ 0.1, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6, and x + y + z = 1. Me represents at least one selected from Sr, Ca, and Ba.) A plurality of piezoelectric layers mainly composed of a composite oxide represented by: and an internal electrode formed between these piezoelectric layers and containing Cu And a piezoelectric layer including at least one component represented by CuOx (x ≧ 0).

In a multilayer piezoelectric element including an internal electrode layer containing Cu, the decrease in electric resistance at a high temperature (100 ° C. to 200 ° C.) is improved because the piezoelectric layer contains CuO _x . Further, the decrease of the electromechanical coupling coefficient kr at this time is a level that hardly causes a problem. Although details are not clear about the reason, it is a fact confirmed by experiments that the decrease in electrical resistance at high temperature is remarkably improved by the presence of Cu.

In order to make Cu exist in the piezoelectric layer, Cu contained in the internal electrode layer may be diffused or added separately to the raw material composition of the piezoelectric layer. This is defined by the manufacturing method of the present invention. That is, the method of fabricating the multilayer piezoelectric element of the present _{invention, (Pb a-b Me b} ) [(Zn 1/3 Nb 2/3) x Ti y Zr z] O 3 ( however, 0.96 ≦ a ≦ 1.03, 0 <b ≦ 0.1, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6, and x + y + z = 1. Me in the formula represents at least one selected from Sr, Ca, and Ba.) A plurality of piezoelectric layers mainly composed of a composite oxide represented by the formula: and Cu formed between these piezoelectric layers. A method of manufacturing a multilayer piezoelectric element including an internal electrode layer is characterized in that Cu contained in the internal electrode layer is diffused into the piezoelectric layer by firing under a reduction firing condition. Alternatively, an additive species containing Cu is added to the raw material matrix composition of the piezoelectric layer, and firing is performed under reducing firing conditions. In any case, the component represented by CuO _x (x ≧ 0) is included in the piezoelectric layer by firing under the reducing firing condition.

  According to the present invention, even when Cu is used as the electrode material of the internal electrode layer, it is possible to provide a multilayer piezoelectric element that has a small decrease in electrical resistance at high temperatures and is excellent in electromechanical coupling coefficient kr. Is possible. Therefore, according to the present invention, it is possible to provide a multilayer piezoelectric element that is inexpensive and has excellent insulation characteristics and high reliability.

  Hereinafter, a multilayer piezoelectric element to which the present invention is applied and a manufacturing method thereof will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a laminated piezoelectric element. As shown in FIG. 1, the multilayer piezoelectric element 1 includes a multilayer body 4 in which an internal electrode layer 3 is inserted between a plurality of piezoelectric layers 2, and this multilayer body 4 contributes to displacement as an active portion. To do. Although the thickness per layer of the piezoelectric layer 2 can be set arbitrarily, it is usually set to about 1 μm to 100 μm, for example. On both sides of the multilayer body 4, there are piezoelectric layer regions in which the internal electrode layer 3 is not formed as inactive regions. The thickness of the piezoelectric layer in this portion is the thickness of the piezoelectric layer 2 between the internal electrode layers 3. In some cases, the thickness is set to be thicker.

  The internal electrode layers 3 are alternately extended in opposite directions, for example, and terminal electrodes 5 and 6 electrically connected to the internal electrode layers 3 are provided at end portions in the extension directions. The terminal electrodes 5 and 6 may be formed, for example, by sputtering a metal such as Au, or may be formed by baking an electrode paste. The thicknesses of the terminal electrodes 5 and 6 are appropriately set depending on the application, the size of the multilayer piezoelectric element 1 and the like, but are usually about 10 μm to 50 μm.

  In the piezoelectric element of the present invention, the internal electrode layer 3 has a function as an electrode for applying a voltage to each piezoelectric layer 2 and is naturally formed of a conductive material. In this case, a noble metal such as Ag, Au, Pt, or Pd can be used as the conductive material, but in the present invention, an electrode material containing Cu is used. Specifically, the internal electrode layer 3 is formed by applying a Cu paste. By using Cu as an electrode material, the manufacturing cost of the multilayer piezoelectric element 1 can be reduced.

On the other hand, a piezoelectric ceramic composition is used for the piezoelectric layer 2, and the piezoelectric ceramic composition used is mainly composed of a composite oxide containing Pb, Ti, and Zr as constituent elements. Here, the composite oxide is composed of, for example, lead titanate (PbTiO ₃ ), lead zirconate (PbZrO ₃ ), and zinc / lead niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ]. Or a composite oxide obtained by substituting a part of Pb with Sr, Ba, Ca, or the like in the ternary composite oxide.

  Specific examples of the composition include composite oxides represented by the following formula (1) or (2). In these formulas (1) and (2), the oxygen composition is obtained stoichiometrically, and deviation from the stoichiometric composition is allowed in the actual composition. .

Pb _a [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (1)
(However, 0.96 ≦ a ≦ 1.03, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6, and x + y + z = 1.)

(Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (2)
(However, 0.96 ≦ a ≦ 1.03, 0 <b ≦ 0.1, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6 X + y + z = 1, and Me in the formula represents at least one selected from Sr, Ca, and Ba.)

  The composite oxide has a so-called perovskite structure, and Pb and the substitution element Me in the formula (2) are located at a so-called A site of the perovskite structure. Zn, Nb, Ti, and Zr are located at the so-called B site of the perovskite structure.

  In the composite oxide represented by the formula (1) or formula (2), the ratio a of the A site element is preferably 0.96 ≦ a ≦ 1.03. If the A-site element ratio a is less than 0.96, firing at low temperatures may be difficult. On the contrary, when the ratio a of the A site element exceeds 1.03, the density of the obtained piezoelectric ceramic is lowered, and as a result, sufficient piezoelectric characteristics may not be obtained, and the mechanical strength may also be lowered. is there.

  In the composite oxide represented by the above formula (2), a part of Pb is substituted with the substitution element Me (Sr, Ca, Ba), but this can increase the piezoelectric strain constant. However, if the substitution amount b of the substitution element Me is too large, the sinterability is lowered, and as a result, the piezoelectric strain constant is reduced and the mechanical strength is also lowered. Also, the Curie temperature tends to decrease as the substitution amount b increases. Therefore, the substitution amount b of the substitution element Me is preferably 0.1 or less.

  On the other hand, among the B site elements, the ratio x between Zn and Nb is preferably 0.05 ≦ x ≦ 0.15. The ratio x affects the firing temperature. If this value is less than 0.05, the effect of lowering the firing temperature may be insufficient. On the other hand, if it exceeds 0.15, the sinterability is affected, and as a result, the piezoelectric strain constant may be reduced and the mechanical strength may be reduced.

  Of the B-site elements, the Ti ratio y and the Zr ratio z are preferably set in terms of piezoelectric characteristics. Specifically, the Ti ratio y is preferably 0.25 ≦ y ≦ 0.5, and the Zr ratio z is preferably 0.35 ≦ z ≦ 0.6. By setting it within the above range, a large piezoelectric strain constant can be obtained in the vicinity of the morphotropic phase boundary (MPB).

The piezoelectric ceramic composition may contain a subcomponent in addition to the main component. In this case, the subcomponent is at least one selected from Ta, Sb, Nb, and W. By adding the subcomponent, the piezoelectric characteristics and the mechanical strength can be improved. However, the content of these subcomponents is preferably 1.0% by mass or less in terms of oxide. For example, in the case of Ta, 1.0% by mass or less in terms of Ta ₂ O ₅ , in the case of Sb, 1.0% by mass or less in terms of Sb ₂ O ₃ , and in the case of Nb, 1.0% by mass in terms of Nb ₂ O ₅ Hereinafter, in the case of W, it is 1.0 mass% or less in terms of WO ₃ . When the content of the second subcomponent exceeds 1.0% by mass in terms of the oxide, the sinterability may be reduced and the piezoelectric characteristics may be deteriorated.

The above is the basic configuration of the multilayer piezoelectric element 1 of the present invention. What is characteristic of the multilayer piezoelectric element 1 of the present invention is that the piezoelectric layer 2 is represented by CuO _x (x ≧ 0). It contains at least one component. Here, examples of CuO _x (x ≧ 0) include Cu oxide in any oxidation state, such as Cu ₂ O and CuO, or Cu (x = 0). It may be included.

When the piezoelectric layer 2 contains CuO _x (x ≧ 0), a decrease in electric resistance at a high temperature is suppressed, and the insulation characteristics are greatly improved. However, _if the content of CuO _x (x ≧ 0) becomes too large, the electromechanical coupling coefficient kr may decrease, so the content is 3.0% by mass or less (however, 0 is not included). It is preferable that When the content of CuO _{x (x} ≧ 0) exceeds 3.0 mass%, the electromechanical coupling factor kr may become 50 or less. More preferably, it is 0.01-3.0 mass%.

The CuO _x (x ≧ 0) contained in the piezoelectric layer 2 may be generated by the diffusion of Cu contained in the internal electrode layer 3 into the piezoelectric layer 2, or the piezoelectric body. It may be added to the layer 2 at the time of the raw material composition and included in the piezoelectric layer 2. In the present invention, it is important that the piezoelectric layer 2 contains Cu, and the addition method and the existence form thereof are not limited.

Another feature of the multilayer piezoelectric element of the present invention is that it is fired under reducing firing conditions. When the laminated piezoelectric element is manufactured, if it is fired in an oxidizing atmosphere, for example, a noble metal needs to be used as the electrode material of the internal electrode layer 3. On the other hand, since the multilayer piezoelectric element of the present invention is fired under reducing firing conditions, inexpensive Cu can be used for the internal electrode layer 3. Here, the reducing firing conditions are, for example, a firing temperature of 800 ° C. to 1200 ° C. and an oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm.

When firing under the reduction firing condition, a decrease in electrical resistance at a high temperature becomes a problem. However, in the case of the multilayer piezoelectric element of the present invention, the piezoelectric layer 2 is CuO _x (x ≧ 0) as described above. This can be avoided. That is, since the multilayer piezoelectric element of the present invention is fired under reducing firing conditions, it is possible to use Cu for the internal electrode layer 3 and to eliminate a decrease in electrical resistance at high temperatures. is there.

  Next, a manufacturing method of the multilayer piezoelectric element having the above configuration will be described. In the production of the multilayer piezoelectric element, first, a vehicle is added to the piezoelectric ceramic composition powder obtained by pulverizing the calcined product, and kneaded to prepare a piezoelectric layer paste. At the same time, Cu powder, which is a conductive material, is kneaded with a vehicle to produce an internal electrode paste. In addition, you may add additives, such as a dispersing agent, a plasticizer, a dielectric material, an insulating material, to the paste for internal electrodes as needed.

Subsequently, by using the piezoelectric layer paste and the internal electrode paste, a green chip that is a precursor of the multilayer body 4 is manufactured by a printing method, a sheet method, or the like. Furthermore, a binder removal process is performed, and the laminate 4 is obtained by firing under reducing firing conditions. As reducing firing conditions, firing is performed at a firing temperature of 800 ° C. to 1200 ° C. in a reducing atmosphere (for example, oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm). The obtained laminate 4 is subjected to terminal polishing by barrel polishing or sand blasting, for example, by sputtering a metal, or by printing or transferring a terminal electrode paste produced in the same manner as the internal electrode paste, Electrodes 5 and 6 are formed.

In the above-described manufacturing process, Cu contained in the internal electrode paste diffuses into the piezoelectric layer 2 formed by firing the piezoelectric layer paste in the process of firing under reducing firing conditions to form the laminate 4. Thereby, CuO _x (x ≧ 0) is included in the piezoelectric layer 2, and the multilayer piezoelectric element of the present invention is manufactured.

  In the diffusion, the particle size of Cu contained in the internal electrode paste affects the diffusion amount. When the particle size of Cu contained in the internal electrode paste is large, the amount of diffusion increases, and when the particle size of Cu is small, the amount of diffusion decreases. If a small amount of Cu is present in the piezoelectric layer 2, the high-temperature electrical resistance is improved. Therefore, it is desirable that the amount of diffusion of Cu is small so as not to deteriorate other characteristics. It is desirable that the particle size of the particles be as small as possible.

In addition, when Cu is included in the raw material composition of the piezoelectric layer paste, the method for manufacturing the multilayer piezoelectric element is as follows. First, for example, PbO powder, ZnO powder, Nb ₂ O ₅ powder, TiO ₂ powder, and ZrO ₂ powder are prepared as the main component raw materials. When the main component is a complex oxide represented by the formula (2), at least one of SrCO ₃ powder, BaCO ₃ powder, and CaCO ₃ powder is further prepared.

Furthermore, at least one of Cu, Cu ₂ O, and CuO is prepared as an additive species of Cu. When subcomponents are added in addition to the main component, necessary ones are prepared from Ta ₂ O ₅ powder, Sb ₂ O ₃ powder, Nb ₂ O ₅ powder, and WO ₃ powder.

  The oxide powder or carbonate powder exemplified as the raw material of the main component and the raw material of the subcomponent is not limited to this, and any material may be used as long as it becomes an oxide by firing. Also good. For example, carbonate powder, oxalate powder, hydroxide powder, or the like can be used instead of the exemplified oxide powder. Similarly, oxide powder, oxalate powder, hydroxide powder, or the like can be used instead of the exemplified carbonate powder.

  Next, after sufficiently drying these raw materials, the respective raw materials are weighed according to a desired final composition, and are sufficiently mixed in an organic solvent or in water using, for example, a ball mill or the like. After drying this, for example, it is calcined at about 700 to 950 ° C. for 1 to 4 hours. Subsequently, the calcined product is sufficiently pulverized in an organic solvent or water using, for example, a ball mill or the like, dried, and then a binder such as polyvinyl alcohol or an acrylic resin is added to prepare a piezoelectric layer paste.

The subsequent steps are the same as in the case of the previous diffusion, and a green chip that is a precursor of the laminate 4 is manufactured by a printing method, a sheet method, or the like using the prepared piezoelectric layer paste and the internal electrode paste. Furthermore, a binder removal process is performed, and the laminate 4 is obtained by firing under reducing firing conditions. As reducing firing conditions, firing is performed at a firing temperature of 800 ° C. to 1200 ° C. in a reducing atmosphere (for example, oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm). The obtained laminate 4 is subjected to terminal polishing by barrel polishing or sand blasting, for example, by sputtering a metal, or by printing or transferring a terminal electrode paste produced in the same manner as the internal electrode paste, Electrodes 5 and 6 are formed.

In the manufacturing method, as described above, firing is carried out under reducing firing conditions and at a relatively low temperature. For example, there is no restriction on the electrode material used for the internal electrode layer, and Cu can be used. Moreover, the deterioration of the high-temperature electrical resistance due to firing under reducing firing conditions is eliminated by adding CuO _x (x ≧ 0), and there is no problem in terms of characteristics.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results.

Experiment 1-1: Confirmation of effect by diffusing Cu An experimental piezoelectric ceramic composition was prepared as follows. First, PbO powder, SrCO ₃ powder, ZnO powder, Nb ₂ O ₅ powder, TiO ₂ powder, and ZrO ₂ powder were prepared as raw materials of the main component, and weighed so as to have the following main component composition. Next, these raw materials were wet-mixed for 16 hours using a ball mill, and calcined at 700 ° C. to 900 ° C. for 2 hours in the air.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

The obtained calcined product was finely pulverized and then wet pulverized for 16 hours using a ball mill. After drying this, an acrylic resin was added as a binder for granulation, and it was formed into a disk shape having a diameter of 17 mm and a thickness of 1 mm using a uniaxial press molding machine at a pressure of about 445 MPa. After molding, a Cu paste containing Cu powder having a particle size of 1.0 μm was printed on both sides. The obtained pellets were heat-treated to volatilize the binder and fired at 950 ° C. for 8 hours in a low oxygen reducing atmosphere (oxygen partial pressure 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm). The obtained sintered body was formed into a disk shape having a thickness of 0.6 mm by slicing and lapping, and the printed Cu paste was removed, and at the same time processed into a shape capable of evaluating the characteristics. A silver paste was printed on both surfaces of the obtained sample and baked at 350 ° C., and an electric field of 3 kV was applied in 120 ° C. silicone oil for 15 minutes to carry out polarization treatment.

  Example 1-1 was produced according to the above method, and Comparative Example 1-1 was produced without printing the Cu paste. About the produced Example and comparative example, electrical resistance IR was measured and the electromechanical coupling coefficient kr was further measured. The electromechanical coupling coefficient kr was measured using an impedance analyzer (HP4194A, manufactured by Hewlett-Packard Company). The results are shown in Table 1. In the table, the electric resistance IR (relative value) is a value obtained by dividing the resistance value at 150 ° C. in each example by the resistance value at 150 ° C. in the case of no addition (Comparative Example 1-1).

In Example 1-1 in which the Cu paste was printed, it can be seen that the electrical resistance at high temperature was greatly improved. Although the characteristics (electromechanical coupling coefficient kr) were slightly lowered, they were sufficiently resistant to use. Therefore, next, ICP analysis was performed on Example 1-1. As a sample preparation method for ICP, first, 1 g of Li ₂ B ₂ O ₇ was added to 0.1 g of a sample to be analyzed, and melted at 1050 ° C. for 15 minutes. To the obtained melt, 0.2 g of (COOH) ₂ and 10 ml of HCl were added, dissolved by heating, and the volume was adjusted to 100 ml. The measurement was performed using ICP-AES (manufactured by Shimadzu Corporation, trade name ICPS-8000). As a result, it was found that about 0.1% by mass of Cu was contained in terms of CuO.

Experiment 1-2: Study on the composition a of the main component A-site element The composition of the main component was set as follows, and the composition a was changed in the composition to prepare Examples 2-1 to 2-4. The method for producing the piezoelectric ceramic composition is the same as in Experiment 1-1. For each of these examples, the electrical resistance IR (relative value) and the electromechanical coupling coefficient kr were measured as in Experiment 1-1. The results are shown in Table 2.
Main component: (Pb _{a -0.03} Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As is apparent from Table 2, even when the composition a is changed within the range defined by the present invention, the effect of diffusing Cu is obtained, and in any of the examples, the electrical resistance at high temperature is large. It has been improved.

Experiment 1-3: Study on the composition b of the main component A site element The compositions of the main component were as follows, and the composition b was changed in the composition to prepare Examples 3-1 to 3-5. The method for producing the piezoelectric ceramic composition is the same as in Experiment 1-1. For each of these Examples, the electrical resistance IR (relative value) and the electromechanical coupling coefficient kr were measured as in Experiment 1-1 and Experiment 2-1. The results are shown in Table 3.
Main component: (Pb _0.995-b Sr _b ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As is apparent from Table 3, even when the composition b is changed within the range defined by the present invention, the effect of diffusing Cu can be obtained. In any of the examples, the electrical resistance at high temperature is large. It has been improved.

Experiment 1-4: Study on main component A-site substitution element Me Example 4-1 and Example 4 were performed in the same manner as in Experiment 1-1 except that the main-site A-site substitution element Me was changed to Ca or Ba. -2 was produced. Table 4 shows the measurement results of the electrical resistance IR (relative value) and the electromechanical coupling coefficient kr at high temperatures in these examples.
Main component: (Pb _0.995-0.03 Me _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As is apparent from Table 4, even when the substitution element Me at the A site of the main component is changed from Sr to Ca or Ba, the effect of diffusing Cu is obtained, and the electrical resistance at high temperature is greatly improved. Yes.

Experiment 1-5: composition x of B-site element of the main component, y, the composition of the study principal components with respect to the z and as follows, the composition of the B site elements in the composition x, y, and z as shown in Table 6 It changed and produced Example 5-1 to Example 5-7. The method for producing the piezoelectric ceramic composition is the same as in Experiment 1-1. For each of these examples, the electrical resistance IR (relative value) and electromechanical coupling coefficient kr at high temperature were measured as in Experiment 1-1. The results are shown in Table 5.
Main component: (Pb _a-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃

  As is apparent from Table 5, even when the composition x, y, z of the B site element is changed, the effect of diffusing Cu is obtained, the electrical resistance at high temperature is greatly improved, and the electromechanical coupling is achieved. It can be seen that the decrease in the coefficient kr is suppressed. However, in Example 5-1, in which the composition x, y, z of the B site element is outside the specified range, the electromechanical coupling coefficient kr is small.

Experiment 1-6: Study on addition of _second subcomponent (Ta ₂ O ₅ ) (first subcomponent: Mn)
Example 6-1 to Example 6-6 were prepared by adding Ta ₂ O ₅ as the second subcomponent and changing the amount of addition as shown in Table 6. The method for producing the piezoelectric ceramic composition is the same as in Experiment 1-1. For each of these examples, the electrical resistance IR (relative value) and electromechanical coupling coefficient kr at high temperature were measured as in Experiment 1-1. The results are shown in Table 6.

As is apparent from Table 6, even when Ta ₂ O ₅ is added as the second subcomponent, the effect of diffusing Cu is obtained, the electrical resistance at high temperature is greatly improved, and the electromechanical coupling coefficient kr The decline of the is suppressed. However, if the amount of Ta ₂ O ₅ added is too large, both the high temperature load life and the electromechanical coupling coefficient kr tend to decrease slightly.

Experiment 1-7: Examination concerning types of subcomponents The oxides shown in Table 7 were added as subcomponents in the amounts shown in Table 7 to prepare Examples 7-1 to 7-5. The method for producing the piezoelectric ceramic composition is the same as in Experiment 1-1. For each of these examples, the electrical resistance IR (relative value) and electromechanical coupling coefficient kr at high temperature were measured as in Experiment 1-1. The results are shown in Table 7.

  As is apparent from Table 7, it can be seen that the effect is observed in any additive and addition amount, the electrical resistance at high temperature is high, and the electromechanical coupling coefficient kr is also large.

Experiment 2: Production of Multilayer Piezoelectric Element In producing a multilayer piezoelectric element, first, a piezoelectric ceramic composition powder obtained by pulverizing the calcined product obtained in Experiment 1-1 was added with a vehicle, kneaded, and then paste for a piezoelectric layer. Was made. At the same time, Cu powder as a conductive material was kneaded with a vehicle to produce an internal electrode paste. Subsequently, using the piezoelectric layer paste and the internal electrode paste, a green chip, which is a precursor of the laminate, was produced by a printing method. Furthermore, binder removal processing was performed, and firing was performed under reducing firing conditions to obtain a laminate. As reducing firing conditions, firing was performed at a firing temperature of 800 ° C. to 1200 ° C. in a reducing atmosphere (for example, oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm).

  About the obtained laminated body (Example 8-1), the laminated body cross section was measured using EPMA (EPMA-1600). Further, as in Experiment 1-1, the electrical resistance IR (relative value) at high temperature and the electromechanical coupling coefficient kr were measured. The results are shown in Table 8.

  Although the piezoelectric layer forming the laminated body alone has a low high-temperature electrical resistance, by firing as a laminated body, the electrode Cu diffuses into the piezoelectric layer and the high-temperature electrical resistance is remarkably improved. When the existence state was examined by EPMA, it was found that there was no segregation of Cu as shown in FIG.

Experiment 3: Examination on Cu diffusion amount control by the particle size of Cu contained in Cu paste In the same manner as Experiment 1, the particle size of Cu powder contained in the Cu paste was changed and Example 9-1 to Example 9-3 were changed. Was made. In Example 9-1 and Example 9-3, a porcelain composition composed of PZT powder (lead titanate and lead zirconate) in Cu paste to increase the bonding strength between the electrode layer and the piezoelectric layer. In Example 9-2, Ni powder is added to the Cu paste. The addition amounts of these co-powder and Ni powder are as shown in Table 9. About these Examples, the electrical resistance IR (relative value) measurement and ICP analysis at high temperature were performed similarly to Experiment 1-1. The results are shown in Table 9.

  As a result, it was found that the amount of diffusion can be changed by changing the particle size of Cu in the Cu paste. Specifically, the smaller the particle size of Cu, the smaller the amount of diffusion. If Cu is present even in a trace amount, the high-temperature electrical resistance is improved. Therefore, it can be said that a smaller amount of Cu diffusion is more desirable in order not to deteriorate the characteristics.

Experiment 4: An additive piezoelectric ceramic composition of Cu as a component of the piezoelectric layer was prepared as follows. First, PbO powder, SrCO ₃ powder, ZnO powder, Nb ₂ O ₅ powder, TiO ₂ powder, and ZrO ₂ powder were prepared as raw materials of the main component, and weighed so as to have the following main component composition. Next, these raw materials were wet-mixed for 16 hours using a ball mill, and calcined at 700 ° C. to 900 ° C. for 2 hours in the air.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

The obtained calcined product was finely pulverized, then a CuO _x (x ≧ 0) raw material (added species: CuO) was added, and wet pulverized for 16 hours using a ball mill. After drying, a vehicle was added and kneaded to prepare a piezoelectric layer paste. At the same time, Cu powder as a conductive material was kneaded with a vehicle to produce an internal electrode paste. Subsequently, using the piezoelectric layer paste and the internal electrode paste, a green chip, which is a precursor of the laminate, was produced by a printing method. Furthermore, binder removal processing was performed, and firing was performed under reducing firing conditions to obtain a laminate. As reducing firing conditions, firing was performed at a firing temperature of 800 ° C. to 1200 ° C. in a reducing atmosphere (for example, oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm).

About the obtained laminated body (Example 10-1), the electrical resistance IR (relative value) and dielectric constant (epsilon) in high temperature were measured similarly to Experiment 1-1. The results are shown in Table 10.

  By adding Cu to the piezoelectric layer, the electrical resistance at high temperature was greatly improved as in the case where Cu was diffused. Further, the decrease in dielectric constant ε at that time is slight.

It is a schematic sectional drawing which shows one structural example of a lamination type piezoelectric element. It is a cross-sectional EPMA photograph of Cu internal electrode laminated body produced in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laminated piezoelectric element, 2 Piezoelectric layer, 3 Internal electrode, 4 Laminated body, 5, 6 Terminal electrode

Claims (7)

(Pb _ab Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (where 0.96 ≦ a ≦ 1.03, 0 <b ≦ 0.1, 0. 05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6, x + y + z = 1 In addition, Me in the formula is selected from Sr, Ca, and Ba. A multilayer piezoelectric element including a plurality of piezoelectric layers mainly composed of a composite oxide represented by (2) and an internal electrode layer formed between the piezoelectric layers and containing Cu. ,
The multilayer piezoelectric element, wherein the piezoelectric layer contains at least one component represented by CuOx (x ≧ 0). The multilayer piezoelectric element according to claim 1, wherein the content of CuO _x (x ≧ 0) is 3.0% by mass or less (however, 0 is not included) in terms of CuO. The multilayer piezoelectric element according to claim 1, wherein the CuO _x (x ≧ 0) is diffused from the internal electrode layer. The multilayer piezoelectric element according to claim 1, wherein the CuO _x (x ≧ 0) is added to the piezoelectric layer as an additive. (Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (However, 0.96 ≦ a ≦ 1.03, 0 <b ≦ 0.1, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6 X + y + z = 1, and Me in the formula represents at least one selected from Sr, Ca, and Ba). A method of manufacturing a laminated piezoelectric element comprising an internal electrode layer formed between piezoelectric layers and containing Cu,
A method of manufacturing a multilayer piezoelectric element, characterized in that Cu contained in the internal electrode layer is diffused into the piezoelectric layer by firing under a reduction firing condition. (Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (However, 0.96 ≦ a ≦ 1.03, 0 <b ≦ 0.1, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6 X + y + z = 1, and Me in the formula represents at least one selected from Sr, Ca, and Ba). A method of manufacturing a laminated piezoelectric element comprising an internal electrode layer formed between piezoelectric layers and containing Cu,
A method of manufacturing a multilayer piezoelectric element, comprising adding an additive species containing Cu to the raw material matrix composition of the piezoelectric layer and performing firing under reducing firing conditions. The reduction firing conditions are firing temperature 800 ° C. to 1200 ° C., oxygen partial pressure 1 × 10 ^-10 ~ 1x10 ^-6 The method for manufacturing a laminated piezoelectric element according to claim 5 or 6, wherein the pressure is atmospheric pressure.

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