JP2014170795A - Laminate and piezoelectric/electrostrictive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate capable of improving a coverage factor of a noble metal film formed on an inorganic substrate and to provide a piezoelectric/electrostrictive element.SOLUTION: A piezoelectric/electrostrictive element 20 includes: a first electrode 21 and a piezoelectric body 22, wherein the first electrode 21 contains a noble metal and boron. A content of boron in the first electrode 21 is 15 ppm or more.

Description

  The present invention relates to a laminate including an inorganic substrate and a noble metal film, and a piezoelectric / electrostrictive element.

  Conventionally, a piezoelectric / electrostrictive element including an inorganic substrate made of a ceramic material and a noble metal film disposed on the inorganic substrate has been widely used.

  Here, in order to prevent the noble metal film from agglomerating during the heat treatment, a method of rapidly heating and rapidly cooling the noble metal film before the heat treatment has been proposed (see Patent Document 1).

JP 2001-303257 A

  However, the method of Patent Document 1 is not suitable for mass production because it requires preparation of expensive equipment for rapid heating and rapid cooling and increases the number of processing steps.

  Therefore, technological development for simply improving the coverage of the noble metal film is expected. Such a technique is not limited to a piezoelectric / electrostrictive element, and is useful when, for example, a noble metal film is formed on a decorative inorganic substrate.

  The present invention has been made in view of the above situation, and an object thereof is to provide a laminate and a piezoelectric / electrostrictive element capable of improving the coverage of a noble metal film formed on an inorganic substrate.

  The laminate according to the present invention includes an inorganic substrate and a noble metal film. The inorganic substrate is made of an inorganic material. The noble metal film is disposed on the inorganic substrate and contains a noble metal and boron. The boron content in the noble metal film is 15 ppm or more.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated body and piezoelectric / electrostrictive element which can improve the coverage of the noble metal film formed on an inorganic substrate can be provided.

Plan view showing the configuration of the actuator XX sectional view of FIG. Graph showing an example of boron concentration distribution in the thickness direction of the first electrode The figure for demonstrating the electrode pattern which concerns on an Example. Binary image of sample No.2 Binary image of sample No.7 Graph showing the strength distribution of boron, noble metal and zirconia in sample No. 7

  Next, an actuator including a piezoelectric / electrostrictive element to which the laminate according to the present invention is applied will be described with reference to the drawings. However, the laminated body according to the present invention can be applied to various structures other than the piezoelectric / electrostrictive element.

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Configuration of actuator 100)
The configuration of the actuator 100 will be described with reference to the drawings. FIG. 1 is a plan view showing the configuration of the actuator 100. FIG. 2 is a sectional view taken along line XX in FIG.

  The actuator 100 includes a base 10 and a piezoelectric / electrostrictive element 20.

  The base 10 is a plate-like member made of a ceramic material. The base 10 has a recess 10a formed on the bottom surface. By forming the recess 10a, the bending displacement of the piezoelectric / electrostrictive element 20 can be increased. The recess may be rectangular as shown in FIG. 1, and may be a square, polygon, circle, ellipse, or a shape with a constriction.

  The material of the substrate 10 includes, for example, at least one selected from the group consisting of stabilized zirconium oxide, aluminum oxide, magnesium oxide, mullite, aluminum nitride, and silicon nitride, and is excellent in mechanical strength and toughness. Stabilized zirconium oxide is particularly preferred.

  The piezoelectric / electrostrictive element 20 is disposed on the upper surface of the substrate 10. The piezoelectric / electrostrictive element 20 includes a first electrode 21, a piezoelectric body 22, and a second electrode 23.

  The first electrode 21 is an example of a noble metal film disposed on the substrate 10. In the present embodiment, the planar shape of the first electrode 21 is a rectangular shape with two corners cut off, but is not limited thereto. The planar shape of the first electrode 21 may be a comb shape, a sandwich shape, a tiger skin shape, or the like.

  The first electrode 21 contains a noble metal as a main component. Examples of the noble metal contained in the first electrode 21 include at least one selected from Pt, Au, Ag, Rh, Pd and Ir, or alloys thereof. In the present embodiment, the composition X “contains the substance Y as the main component” means that the substance Y preferably accounts for 60% by weight or more, more preferably 70% by weight or more in the entire composition X. More preferably 90% by weight or more.

  The first electrode 21 contains boron. The boron content in the first electrode 21 is preferably 15 ppm or more. Thereby, the thickness of the first electrode 21 is suppressed from being locally reduced, and a coverage of 90% or more by the first electrode 21 can be achieved.

  The boron content is determined by measuring the strength of boron and noble metal with a GD-OES (glow discharge optical emission spectrometry) device in the cross section of the first electrode 21 and calculating the ratio of the cumulative strength of boron to the cumulative strength of noble metal. Can be obtained. Therefore, in the present embodiment, the boron content in the first electrode 21 is the ratio of the boron concentration to the noble metal concentration. Therefore, when the first electrode 21 contains a substance other than the noble metal and boron, the presence of the substance should be excluded, and the boron content should be calculated by focusing only on the concentration of the noble metal and boron. is there.

  Furthermore, the boron content in the first electrode 21 is more preferably 40 ppm or more and 700 ppm or less. As a result, a coverage of 99% or more by the first electrode 21 can be achieved.

  The coverage can be calculated from the ratio between the black area shielded by the first electrode 21 and the white area through which light is transmitted when light is irradiated from the substrate 10 side.

  Here, FIG. 3 is a graph showing an example of the concentration distribution of boron and noble metal in the thickness direction of the first electrode 21. Such a graph can be created by measuring the intensity distribution of boron and noble metals with a GD-OES (Glow Discharge Optical Emission Spectroscopy) apparatus. Specifically, since the strength of boron and noble metal correlates with the concentration of boron and noble metal, the concentration distribution can be grasped by normalizing the strength.

  As shown in FIG. 3, the concentration of boron decreases from the inside of the first electrode 21 toward the surface. In other words, the concentration of boron in the first electrode 21 is highest at the center of the first electrode 21 and lowest at the surface of the first electrode 21.

  Further, the half-value width W1 of the boron concentration distribution is smaller than the half-value width W2 of the noble metal concentration distribution. Thereby, boron is confined inside the first electrode 21, and the concentration of boron in the vicinity of the surface of the first electrode 21 can be reduced. Therefore, when a voltage is applied to the first electrode 21, it is possible to suppress the phenomenon (so-called ion migration) in which boron moves to the piezoelectric body 22.

  The piezoelectric body 22 is an example of an inorganic substrate made of an inorganic material. The piezoelectric body 22 is formed in a plate shape and has a first main surface 22S and a second main surface 22T as shown in FIG. The first electrode 21 is disposed on the first major surface 22S, and the second electrode 23 is disposed on the second major surface 22T.

  As a material of the piezoelectric body 22, a conventionally used ceramic material for piezoelectric bodies can be used. Specific examples of such ceramic materials include lead zirconate, lead titanate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead antimony stannate, lead manganese tungstate. , A material selected from lead cobalt niobate, barium titanate, sodium bismuth titanate, potassium sodium niobate, strontium bismuth tantalate, and the like. In particular, a material having a high electromechanical coupling coefficient and a piezoelectric constant, a low reactivity with the substrate portion made of ceramics at the time of sintering the piezoelectric / electrostrictive film, and a stable composition are suitable. Examples of such a material include a material mainly composed of lead zirconate titanate (PZT) and lead magnesium niobate (PMN), a material mainly composed of sodium bismuth titanate, and lead titanate-lead zirconate. -A ternary solid solution composition of lead magnesium niobate as a main component, a material in which nickel oxide and silicon oxide are added, and a ternary solid solution composition of lead titanate-lead zirconate-bismuth nickel niobate The material which has as a main component is mentioned.

  The material of the piezoelectric body 22 described above includes lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium, tantalum, lithium, One material selected from oxides such as bismuth and tin, or a mixture of a plurality of materials may be added. For example, by adding lanthanum or strontium to a ceramic material that contains lead zirconate, lead titanate, and lead magnesium niobate as main components, the electric field and piezoelectric characteristics can be adjusted. In addition, in order to lower the firing temperature without significantly degrading the characteristics, eutectic compounds of lead oxide and bismuth oxide are added to ceramic materials containing lithium compounds such as lithium carbonate, lithium fluoride, or lithium borate as main components. May be added.

  The second electrode 23 is disposed on the piezoelectric body 22. As the material of the second electrode 23, the same material as that of the first electrode 21 can be used. However, the second electrode 23 may not contain boron.

(Manufacturing method of actuator 100)
Next, a method for manufacturing the actuator 100 will be described.

  First, the substrate 10 is manufactured by forming a ceramic material for the substrate 10 into a desired shape and then firing it. Specifically, first, a slurry composed of ceramic powder, vehicle, dispersant, plasticizer and solvent is prepared. Next, the slurry is kneaded and then dried to form a clay-like substrate. Next, the substrate 10 having the recesses 10a is formed by pressing the substrate with a mold having the protrusions corresponding to the recesses 10a and firing it under predetermined conditions. In addition, the recessed part 10a can also be formed by forming a green sheet with the above-mentioned slurry, punching a plurality of green sheets with a punch, and laminating.

  Next, the surface is roughened by immersing the substrate 10 in heated hydrofluoric acid (HF) for 10 minutes.

  Next, a photoresist having a predetermined pattern (see FIG. 1) is developed on the surface of the substrate 10.

  Next, after applying noble metal atoms serving as catalyst nuclei for electroless plating onto the substrate 10 by sputtering, patterning is performed by removing the photoresist.

  Next, an appropriate amount of boron oxide is added to a mixed solution of a basic solution of a noble metal plating solution, a reducing agent, an aqueous ammonia solution and pure water, and then stirred with a magnetic stirrer until stable at 60 ° C., and a noble metal plating solution is erected.

  Next, electroless plating is performed by immersing the base 10 including the catalyst core in a noble metal plating solution. Thereby, the first electrode 21 containing a noble metal and boron is patterned.

  Next, the substrate 10 on which the first electrode 21 is patterned is put into an electric furnace, heated under predetermined conditions, and then naturally cooled to room temperature. At this time, boron contained in the first electrode 21 reduces the sinterability of the noble metal, thereby suppressing aggregation associated with the noble metal grain growth. As a result, local thinning of the noble metal material is suppressed, and the first electrode 21 has a uniform thickness as a whole.

  Next, a green sheet made of ceramic powder, a vehicle, a dispersant, and a plasticizer for the piezoelectric body 22 is disposed on the first electrode 21.

  Next, after degreasing the green sheet by heating to a predetermined temperature, the green sheet is put into an electric furnace, heated under predetermined conditions, and naturally cooled to room temperature.

  Next, the second electrode 23 is formed by applying a precious metal paste, resinate, or colloidal ink onto the piezoelectric body 22 and baking it by a method such as screen printing, spin coating, spray coating, or the like.

(Function and effect)
(1) The boron content in the first electrode 21 is 15 ppm or more. Thereby, since it can suppress that the thickness of the 1st electrode 21 becomes thin locally, the coverage of the 1st electrode 21 can be improved simply.

  (2) The half-value width W1 of the boron concentration distribution is smaller than the half-value width W2 of the noble metal concentration distribution. As a result, the concentration of boron on the surface of the first electrode 21 is reduced, and the occurrence of ion migration can be suppressed.

(Other embodiments)
The present invention is not limited to the embodiment described above, and various modifications or changes can be made without departing from the scope of the present invention.

  For example, in the above embodiment, the first electrode 21 is formed by electroless plating, but it can also be formed by electrolytic plating, sputtering, vapor deposition, or the like. Moreover, when you may form in thickness of 1 micrometer or more, the 1st electrode 21 can be formed by the apply | coating method.

  Moreover, although the said embodiment demonstrated the case where the laminated body which concerns on this invention was applied to the piezoelectric / electrostrictive element, the laminated body which concerns on this invention is applicable to other various structures. For example, the laminate according to the present invention can be applied to a decorative member in which a noble metal film is formed on a decorative inorganic substrate.

  Moreover, in the said embodiment, although the actuator 100 decided to have the recessed part 10a, the laminated body which concerns on this invention is applicable also to the actuator 100 which does not have the recessed part 10a.

  Examples according to the present invention will be described below. However, the present invention is not limited to the examples described below.

[Production of sample No. 1 to No. 9]
Samples No. 1 to No. 9 were produced as follows.

  First, hydrogen fluoride obtained by heating a partially stabilized zirconia substrate having an outer dimension of 40 mm × 30 mm and a thickness of 0.25 mm, in which 300 recesses (85 μm pitch) of 80 μm × 0.8 mm were formed in advance, to 50 ° C. The surface was roughened by dipping in acid for 10 minutes.

  Next, using a photoresist PMER-N (manufactured by Tokyo Ohka Kogyo Co., Ltd.), as shown in FIG. 4, 2 mm × 30 mm line electrodes, 75 μm × 1 mm 300 comb electrodes (85 μm pitch), and 10 mm × A pattern including a 10 mm pad electrode was developed in two rows.

  Next, Pt as a catalyst core for electroless plating was applied to a partially stabilized zirconia substrate by sputtering, and the resist was removed for patterning.

  Next, in a polypropylene container, 100 ml of Lectoroles Pt100 basic solution (manufactured by Nippon Electroplating Engineers, Pt content 0.4 g), 2 ml of reducing agent, 10 ml of pH 12 Aqueous ammonia solution was added, and pure water was further added so that the total amount became 200 ml.

  Next, a predetermined amount of boron oxide (manufactured by Kanto Chemical) was added to the plating solution and stirred with a magnetic stirrer until stable at 60 ° C. The amount of boron oxide added is as shown in Table 1. In sample No. 1, no boron oxide was added.

  Next, the partially stabilized zirconia substrate on which the Pt catalyst nucleus was formed was rocked at 0.5 Hz for 20 minutes while being immersed in the plating solution. Thereby, a Pt plating electrode having a film thickness of 0.5 μm was formed.

  Next, the partially stabilized zirconia substrate was washed with water, dried at 50 ° C. for 10 minutes, and further dried at 100 ° C. for 10 minutes to obtain a partially stabilized zirconia substrate having electrodes patterned thereon.

  Next, the partially stabilized zirconia substrate on which the electrode was formed was placed on an alumina setter and placed in an alumina mortar. At this time, a 5 mm gap was provided with a spacer so that the gas could escape.

  Next, the mortar is put into an electric furnace, heated to a maximum temperature of 1100 ° C at a rate of temperature increase of 200 ° C / h and held for 2 hours, then cooled to 600 ° C at 200 ° C / h, and further to room temperature. Allow to cool. The laminated body which concerns on sample No.1-No.9 was completed by the above.

  Next, a piezoelectric sheet mainly composed of lead zirconate titanate, a vehicle made of polyvinyl butyral, a 6 μm thick green sheet made of a dispersant and a plasticizer was cut and laminated on the electrodes of the laminate.

  Next, the green sheet was degreased at 550 ° C.

  Next, after heating to a maximum temperature of 1000 ° C. at a rate of temperature increase of 500 ° C./h and holding for 2 hours, the temperature was decreased to 600 ° C. at 200 ° C./h, and then naturally cooled to room temperature. Thereby, a piezoelectric ceramic film having a thickness of 3 μm was obtained.

  Next, Au resinate E-9802 (manufactured by NV Chemcat) was screen-printed on the piezoelectric ceramic and fired to form an upper electrode film having a thickness of 0.15 μm.

  Next, using a photolithographic process, the piezoelectric ceramic film and the upper electrode film are patterned with a resist so that they remain in a comb shape, and wet using AURUM-401 (manufactured by Kanto Chemical) and WPZ-2029 (manufactured by ADEKA). Etched. As described above, a piezoelectric / electrostrictive film type element including a comb-shaped piezoelectric ceramic film and an upper electrode film was manufactured.

[Production of sample No. 10 to No. 18]
In Samples No. 1 to No. 9, electrodes were formed by electroless plating. In Samples No. 10 to No. 18, electrodes were formed by electrolytic plating.

  Specifically, after patterning Pt as a catalyst nucleus, 0.05 mol / l dinitroammine platinum solution (Tanaka Kikinzoku Kogyo), 0.85 mol / l sodium acetate (Kanto Chemical) and 0.95 mol / l 1 plating solution of sodium carbonate (manufactured by Kanto Kagaku) was erected.

  Next, a predetermined amount of boron oxide (manufactured by Kanto Chemical) was added to the plating solution and stirred with a magnetic stirrer until stable at 80 ° C. The amount of boron oxide added is as shown in Table 1, but no boron oxide was added in sample No. 10.

Next, the partially stabilized zirconia substrate on which the Pt catalyst nuclei were formed was held for 250 seconds while being immersed in a plating solution having a current density of 100 A / m ² .

  And the laminated body and piezoelectric / electrostrictive film type | mold element of sample No.10-No.18 were produced through the process similar to sample No.1-No.9.

[Production of Sample No. 19 to No. 26]
In the samples No. 1 to No. 9, the Pt electrode was formed by electroless plating, while in Samples No. 19 to No. 26, the Au electrode was formed by electrolytic plating.

  Specifically, after patterning Au as a catalyst nucleus, an Au plating solution NCF-500 (manufactured by NE Chemcat) was constructed.

  Next, a predetermined amount of boron oxide (manufactured by Kanto Chemical Co., Inc.) was added to the plating solution and stirred with a magnetic stirrer until stable at 30 ° C. The amount of boron oxide added is as shown in Table 1, but in sample No. 19, no boron oxide was added.

Next, the partially stabilized zirconia substrate on which the Au catalyst nuclei were formed was held for 250 seconds while immersed in an Au plating solution having a current density of 100 A / m ² .

  And the laminated body and piezoelectric / electrostrictive film type | mold element of sample No. 19-No. 26 were produced through the process similar to sample No. 1-No.

[Electrode coverage]
In the laminates of Samples No. 1 to No. 26, the electrode coverage was measured.

  Specifically, the electrode was imaged with a 500 × microscope (Nikon ECLIPSE LV150N) while irradiating light from the back surface of the partially stabilized zirconia substrate. Next, on the captured image, the light-shielded area and the light-transmitting area were binarized with black / white. And the ratio of the area of the light-shielded area | region with respect to the area of the whole electrode was computed as a coverage (%). The calculation results of the coverage are summarized in Table 1.

  5 is a binarized image of sample No. 2, and FIG. 6 is a binarized image of sample No. 7. As shown in Table 1, the coverage of sample No. 2 was 95%, and the coverage of sample No. 7 was 100%.

[Concentration of components at electrode]
In the laminated body of sample No. 1 to No. 26, the component concentration in the pad electrode was measured.

  Specifically, the strength (concentration) of boron, noble metal (Pt or Au) and zirconia in the thickness direction of the pad electrode was measured using a GD-OES apparatus GD-Profiler2 (manufactured by Horiba). And the half value width and integrated intensity | strength of the intensity distribution (concentration distribution) of boron and a noble metal were measured from the obtained data. Table 1 summarizes the ratio of the half-value width of the boron concentration distribution to the half-value width of the noble metal concentration distribution and the calculation result of the integrated intensity. The ratio (B / Pt or B / Au) of the boron integrated strength to the precious metal integrated strength corresponds to the boron content (concentration) in the electrode.

  FIG. 7 is a graph showing the intensity distribution of boron, Pt and zirconia in sample No. 7. In FIG. 7, not only the Pt electrode but also the intensity distribution in the zirconia substrate is shown.

[Reliability evaluation of piezoelectric / electrostrictive membrane elements]
It was evaluated whether or not ion migration of the added boron occurred in piezoelectric / electrostrictive film type elements other than Sample Nos. 1, 10, and 19.

  Specifically, a piezoelectric / electrostrictive film type element in which a lead was soldered to a pad electrode was placed in a constant temperature and humidity chamber. Next, the lead pulled out from the external port is connected to a DC power source (manufactured by NF circuit) and a multimeter (manufactured by Keithley), and is left for 5 hours with the temperature and humidity chamber kept in an environment of 40 ° C. and humidity of 85%. did. Next, the DC power supply was controlled, and the current value was measured with a multimeter while applying a voltage of 1 V / second from 0 to 60 V. And the resistance value was converted from the applied voltage and the current value.

  In Table 1, samples having an electric resistance value of 1 MΩ · m or more were evaluated as ◎ (no ion migration), and samples having an electric resistance value smaller than 1 MΩ · m were evaluated as ◯ (with ion migration).

As shown in Table 1, in the sample in which the boron content in the noble metal electrode was 15 ppm or more, a coverage of 90% or more could be achieved. This is because the added boron has reduced the sinterability of the noble metal, thereby suppressing the aggregation of the noble metal.

  In addition, in the sample in which the boron content in the noble metal electrode was 40 ppm or more and 700 ppm or less, a coverage of 99% or more could be achieved. This is because the boron content is particularly appropriate and aggregation of the noble metal can be effectively suppressed.

  In addition, in the sample where the ratio of the half-value width of the boron concentration distribution to the half-value width of the noble metal concentration distribution was less than 100%, it was confirmed that the electric resistance value was 1 MΩ · m or more and no ion migration occurred. . This is because boron can be prevented from being deposited on the surface of the noble metal electrode by confining boron inside the noble metal electrode.

  In all samples other than sample Nos. 1, 10, and 19, it was confirmed that the concentration of boron decreased as it approached the surface from the inside, as in FIG.

DESCRIPTION OF SYMBOLS 10 Base body 20 Piezoelectric / electrostrictive element 21 1st electrode 22 Piezoelectric body 23 2nd electrode

Claims (6)

An inorganic substrate composed of an inorganic material;
A noble metal film disposed on an inorganic substrate and containing a noble metal and boron;
With
The boron content in the noble metal film is 15 ppm or more.
Laminated body. The boron content in the noble metal film is 40 ppm or more and 700 ppm or less,
The laminate according to claim 1. The noble metal film contains Pt as a noble metal,
The laminate according to claim 1 or 2. An inorganic substrate composed of an inorganic material;
A first electrode disposed on the first main surface of the inorganic substrate and containing a noble metal and boron;
A second electrode disposed on a second main surface of the inorganic substrate;
With
The boron content in the first electrode is 15 ppm or more.
Piezoelectric / electrostrictive element. The concentration of boron in the thickness direction of the first electrode decreases as it approaches the surface from the inside of the first electrode.
The piezoelectric / electrostrictive element according to claim 4. In the thickness direction of the first electrode, the half-value width of the boron concentration distribution is smaller than the half-value width of the noble metal concentration distribution.
The piezoelectric / electrostrictive element according to claim 4 or 5.