JP4868881B2 - Piezoelectric ceramic composition, piezoelectric ceramic, piezoelectric actuator element and circuit module - Google Patents

Description

  The present invention relates to a piezoelectric ceramic composition, a piezoelectric ceramic, a piezoelectric actuator element, and a circuit module, and in particular, includes a piezoelectric ceramic composition, a piezoelectric ceramic, and a piezoelectric actuator element for obtaining a piezoelectric actuator element capable of surface mounting. Relates to the circuit module.

  Conventionally, there are ultrasonic applied vibrators, ultrasonic motors, piezoelectric actuator elements, etc. that use displacement generated by the piezoelectric effect as a mechanical drive source, and attention has been gathered with the progress of the mechatronics field.

  Especially in recent years, the piezoelectric actuator element can be miniaturized, and due to the features such as high-speed driving and low-voltage driving, the auto-focus lens and zoom of the camera lens module mounted on cameras for mobile terminals, digital cameras, digital video cameras, etc. A practical application as an actuator for driving a lens has been studied, and a multilayered piezoelectric actuator element has attracted attention as a piezoelectric actuator element used in such a small electronic device.

In applications where an actuator mechanism is required as described above, stacked piezoelectric actuator elements characterized by more precise operation and high-speed operation are being reduced in size and being put into practical use in various fields. and a piezoelectric actuator device of a preferred laminated is required to have a high piezoelectric strain constant d ₃₃ to increase the displacement by the piezoelectric properties in various applications.

  In addition, in the process of incorporating the piezoelectric actuator element into the mechanical component, the Curie temperature Tc of the piezoelectric ceramic is increased so that the piezoelectric characteristic does not deteriorate even if the bonding temperature is high, in order to perform strong adhesion with the mechanical component. It is requested.

In order to meet these requirements, a piezoelectric ceramic in which Pb (Zn _1/3 Sb _2/3 ) O ₃ is added to PbZrO ₃ —PbTiO ₃ to form a solid solution has been proposed (for example, patents). Reference 1).
JP 2001-97774 A

However, piezoelectric ceramics disclosed in Patent Document 1, although having a high piezoelectric strain constant d _33, when mounted on the circuit board to the piezoelectric actuator element composed of the piezoelectric ceramic by heating of the reflow or the like, by heating the piezoelectric strain constant d ₃₃ there is a problem that can not be obtained a practical heat resistance will be lowered. For example, in Patent Document 1, reflow heating is performed for several seconds at a temperature of 200 to 250 degrees, but there is a problem that the piezoelectric characteristics of the piezoelectric ceramic deteriorate even in such a short time.

Accordingly, an object of the present invention is to provide a piezoelectric ceramic composition and a piezoelectric ceramic that can suppress a decrease in the piezoelectric strain constant d ₃₃ before and after reflow heating, and a circuit module on which the piezoelectric actuator element is mounted.

The piezoelectric ceramic composition of the present invention comprises Pb (Zr, Ti) O ₃ and Pb (Yb _1/2 M _1/2 ) O ₃ (where M is at least one of Nb or Sb) as the main components. The component includes at least three types of complex oxidation selected from Sr (Zr, Ti) O ₃ , Ba (Zr, Ti) O ₃ , Pb (Ni _1/2 Te _1/2 ) O ₃ and Pb _1/2 NbO _3. It is characterized by comprising a complex oxide having a perovskite structure in which a solid solution is formed.

In the above piezoelectric ceramic composition, _the composition formula by molar ratio of the _{element, Pb 1-x-y Sr} x Ba y (Yb 1/2 M 1/2) a (Ni 1/2 Te 1/2) b Zr c _{Ti 1-a-b-c} O 3 + αPb 1/2 NbO 3 ( where, M is at least one Nb or Sb) when expressed as, x, y, a, b, c and α is (mass%), 0 ≦ x ≦ 0.08, 0 ≦ y ≦ 0.08, 0 <x + y, 0.01 ≦ a ≦ 0.12, 0 ≦ b ≦ 0.02, 0.43 ≦ c ≦ 0.54, 0 ≦ It is desirable to satisfy α ≦ 1.2.

  The piezoelectric ceramic according to the present invention is obtained by firing the above-described piezoelectric ceramic composition, and includes Pb, Zr, Ti, Yb, and M (wherein M is at least one of Nb or Sb) as an element and has a perovskite type crystal phase. A piezoelectric ceramic having a structure is characterized in that when all the crystals are represented by volume fraction, the ratio of tetragonal crystal is 40% or more.

  The piezoelectric actuator element of the present invention is characterized in that an electrode is formed on the surface of the piezoelectric ceramic. Furthermore, the circuit module of the present invention is characterized in that the above-described piezoelectric actuator element is surface-mounted on a circuit board.

According to the present invention, Pb (Zr, Ti) O ₃ and Pb (Yb _1/2 M _1/2 ) O ₃ are the main components, and Sr (Zr, Ti) O ₃ , Ba (Zr) , Ti) O ₃ , Pb (Ni _1/2 Te _1/2 ) O ₃ and Pb _1/2 NbO ₃ are dissolved in solid solution to increase the piezoelectric strain constant d _33. and high has a Curie temperature, it is possible to obtain a piezoelectric ceramic composition to obtain a small piezoelectric actuator element of decrease in piezoelectric constant d ₃₃ before and after reflow heating.

The piezoelectric ceramic obtained from the piezoelectric ceramic composition described above has a degradation of the piezoelectric strain constant d ₃₃ even at high temperatures exceeding 200 ° C. by setting the ratio of tetragonal crystals in the total crystal to 40% or more in volume fraction. A piezoelectric ceramic having a small and high heat resistance can be obtained.

  Further, when an electrode is formed on the surface of the piezoelectric ceramic to form a piezoelectric actuator element, for example, a piezoelectric actuator element that can be surface-mounted on a circuit board by reflow heating using solder is obtained. A piezoelectric actuator element formed by a piezoelectric ceramic having a piezoelectric ceramic element can be easily mounted on a substrate even if the size is small, and a circuit module in which piezoelectric actuator elements are integratedly mounted on a circuit board can be obtained. . Further, with such a piezoelectric actuator element, the displacement amount and heat resistance can be improved, and a stable displacement amount can be obtained for a long period of time.

The piezoelectric ceramic composition of the present invention comprises Pb (Zr, Ti) O ₃ and Pb (Yb _1/2 M _1/2 ) O ₃ (where M is at least one of Nb or Sb) as the main components. The component includes at least three types of complex oxidation selected from Sr (Zr, Ti) O ₃ , Ba (Zr, Ti) O ₃ , Pb (Ni _1/2 Te _1/2 ) O ₃ and Pb _1/2 NbO _3. things which is characterized by comprising a composite oxide having a perovskite structure which is a solid solution, in particular, the composition formula by molar ratio of the element _{Pb 1-x-y Sr x} Ba y (Yb 1 _{/ 2} M _1/2 ) _a (Ni _1/2 Te _1/2 ) _b Zr _c Ti _1-a-b-c O ₃ + αPb _1/2 NbO ₃ (where M is at least one of Nb or Sb) X, y, a, b, c and α (mass%) 0 ≦ x ≦ 0.08, 0 ≦ y ≦ 0.08, 0 <x + y, 0.01 ≦ a ≦ 0.12, 0 ≦ b ≦ 0.02, 0.43 ≦ c ≦ 0.54, It is desirable to satisfy 0 ≦ α ≦ 1.2. Incidentally, Pb (Zr, Ti) with respect to _{O 3, Pb (Yb 1/2 M} 1/2) O 3, Sr (Zr, Ti) O 3, Ba (Zr, Ti) O 3, Pb (Ni 1 _{/ 2} Te _1/2 ) O ₃ and Pb _1/2 NbO ₃ and other complex oxides are solid solution in the evaluation by X-ray diffraction after firing the piezoelectric ceramic composition of the above configuration. A state in which a single phase having a substantially perovskite structure is obtained.

Here, for 0 ≦ x ≦ 0.08, if x is larger than 0.08, the reduction rate of the piezoelectric strain constant d ₃₃ after reflow heating becomes larger than 3%.

For 0 ≦ y ≦ 0.08, if y is greater than 0.08, the rate of decrease of the piezoelectric strain constant d ₃₃ after reflow heating is greater than 3%.

For 0.01 ≦ a ≦ 0.12, the piezoelectric strain constant d ₃₃ decreases when a is smaller than 0.01. On the other hand, if a is greater than 0.12, the rate of decrease of the piezoelectric strain constant d ₃₃ after reflow heating is greater than 3%.

For 0 ≦ b ≦ 0.02, if b is greater than 0.02, the rate of decrease of the piezoelectric strain constant d ₃₃ after reflow heating is greater than 3%.

With respect to 0.43 ≦ c ≦ 0.54, if c is less than 0.43 or c is more than 0.54, the initial piezoelectric strain constant d ₃₃ becomes smaller than 400 × 10 ⁻¹² m / V.

For 0 ≦ α ≦ 1.2, if α is greater than 1.2, the rate of decrease of the piezoelectric strain constant d ₃₃ after reflow heating is greater than 3%.

In the present invention, by introducing Nb or Sb into M of (Yb _1/2 M _1/2 ), a large piezoelectric strain constant d ₃₃ can be obtained while maintaining a high Curie temperature.

Furthermore, sintering at a relatively low temperature of about 1050 to 1100 ° C. can be performed. Therefore, firing at a lower temperature is possible as compared with the conventional piezoelectric ceramic composition, and the ratio of Ag and Pd of the internal electrode is in the range of 80:20 to 70:30 in the case of forming a laminated body such as a piezoelectric actuator element. It is possible to set to, and simultaneous firing. On the other hand, those not containing the M component of the present invention have low heat resistance, and the reduction rate of the piezoelectric strain constant d ₃₃ is greater than 3% after reflow heating.

In addition, since the introduction of an appropriate amount of (Ni _1/2 Te _1/2 ) can increase the coercive electric field Ec while increasing the piezoelectric strain constant d ₃₃ , depolarization in continuous driving when a piezoelectric actuator element is configured. There is an advantage that it contributes to the improvement of durability and heat resistance. Moreover, introduction of an appropriate amount of Pb _1/2 NbO ₃ has the effect of increasing the piezoelectric strain constant d ₃₃ with piezoelectricity.

In the present invention, in particular, 0.03 ≦ x ≦ 0.05, 0.01 ≦ y ≦ 0.03, 0.071 ≦ a ≦ 0.08, 0.004 ≦ b ≦ 0.006, 0.44 ≦ When c ≦ 0.46 and 0.4 ≦ α ≦ 0.6, there are advantages that the piezoelectric strain constant d ₃₃ is 500 × 10 ⁻¹² m / V or more and the heat resistance is good.

Although the ratio of Zr and Ti in the piezoelectric ceramic of the present invention is important to capture the composition phase boundary near the extremum of the piezoelectric strain constant d ₃₃ (MPB), perovskite thereof MPB is represented by ABO ₃ It varies in various ways depending on the type and amount of the element that substitutes for the A site and B site of the structure. The MPB near its composition, tetragonal, for orthorhombic, which is composed of rhombohedral either crystals 1 or more, to obtain a piezoelectric ceramic having a high heat resistance that the piezoelectric strain constant d ₃₃ is not deteriorated at a higher temperature In addition, the ratio of tetragonal crystals in the volume fraction in all crystals is preferably 40% or more, particularly 44% or more and 70% by volume or less, while monoclinic crystals may be present in a ratio of 20 to 55% by volume. However, it is preferable that rhombohedral crystals are not included.

  FIG. 1 is a partial cross-sectional view showing a piezoelectric actuator element of the present invention. The piezoelectric actuator element of the present invention has an internal electrode 3 inside a laminated piezoelectric layer 1, and the thickness of the piezoelectric layer 1 is preferably 10 to 40 μm from the viewpoint of miniaturization of the element.

  If the piezoelectric ceramic having the composition and crystal structure described above is used, for example, a laminated type having a structure in which an electrode of Ag / Pd (= 80/20) to be the internal electrode 3 is printed to partially include the internal electrode, and A micro-type piezoelectric actuator element (a micro-stacked piezoelectric actuator element) can be manufactured.

In the piezoelectric ceramic thus obtained, it is desirable that the piezoelectric strain constant d ₃₃ is 400 × 10 ⁻¹² m / V or more. When the piezoelectric strain constant d ₃₃ is 400 × 10 ⁻¹² m / V or more, there is an advantage that the piezoelectric displacement in the piezoelectric actuator element can be increased.

Electromechanical coupling coefficient _{k 33} is desirably 70% or more. When the electromechanical coupling coefficient k ₃₃ is 70% or more, it is easy to convert electrical energy into mechanical energy (displacement), and there is an advantage that operation with lower power becomes possible.

  The Curie temperature Tc is preferably 265 ° C. or higher, particularly 280 ° C. or higher, and more preferably 290 ° C. or higher.

  FIG. 2 is a schematic cross-sectional view of the circuit module of the present invention. The circuit module of the present invention is obtained by mounting a laminated piezoelectric actuator element 11 on a circuit board 13 provided with an actuator drive circuit using solder. In this figure, a lens 12 is attached between the piezoelectric actuator elements 11. When the high heat-resistant piezoelectric ceramic as described above is used, it becomes possible to surface-mount the laminated piezoelectric actuator element (micro laminated piezoelectric actuator element) 11 on the circuit board 13 by reflow heating. A circuit module such as a micro laminated piezoelectric actuator circuit board in which a drive circuit is configured through the electrode 15 can be obtained.

Next, a method for manufacturing the piezoelectric ceramic according to the present invention will be described. As starting materials, each powder of Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , SrCO ₃ , BaCO ₃ , Yb ₂ O ₃ , Sb ₂ O ₃ , NiO, TeO ₂ and Nb ₂ O ₅ was weighed and put into a ball mill or the like. And wet mix. The mixture is then dehydrated and dried, calcined at a temperature of 850 to 950 ° C. for 1 to 3 hours, and pulverized with a ball mill or the like.

Thereafter, an organic binder (PVA, mobile vinyl, etc.) is added to this pulverized product and kneaded and dried to form granulated powder, and the obtained granulated powder is molded to produce a molded body. At this time, the molding pressure is preferably 1 × 10 ⁸ N / m ² or more so that the sintered piezoelectric ceramic composition is densified and the diameter of voids existing on the surface does not increase. The molded body thus obtained can be obtained by firing at a temperature of 1050 to 1150 ° C. for 1 to 3 hours in a lead atmosphere.

First, Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , SrCO ₃ , BaCO ₃ , ZnO, Sb ₂ O ₃ , NiO, TeO ₂ , and Nb ₂ O ₅ are prepared as raw material powders for the piezoelectric ceramic composition. _{pb 1-x-y Sr x} Ba y (Yb 1/2 M 1/2) a (Ni 1/2 Te 1/2) b Zr c Ti 1-a-b-c O 3 + αPb 1/2 NbO 3 M is set to be at least one of Nb and Sb, the basic components are weighed so that the values of x, y, a, b, c, and α are as shown in Table 1, and the solvent is used for this mixture. Water was added and wet mixed in a ball mill for 20 hours. Next, this mixture was dried and calcined by applying a heat treatment at a temperature of 900 ° C. for 3 hours. Next, water was added and a slurry was prepared by using a ZrO ₂ ball in a ball mill for 20 hours by wet mixing and pulverization. Next, this slurry was kneaded with 5 parts by mass of an organic binder (movinyl) with respect to 100 parts by mass of the raw material powder, and then dried to produce granulated powder, which was molded at 1.5 × 10 ⁸ N / m ² . A cylinder having a diameter of 8 mm and a thickness of 12 mm was formed by pressure, degreased, and then fired at a temperature of about 1100 ° C. to produce a piezoelectric ceramic. Next, the obtained piezoelectric ceramic was processed into φ7 mm and thickness 10 mm, and Ag glass was printed on both sides of φ7 and baked. Thereafter, a direct current voltage was applied for 30 minutes in 100 ° C. silicone oil, and polarization treatment was performed in an electric field of 1.5 kV / mm. Then, what was aged in 150-200 degreeC constant temperature was made into the electrical property evaluation sample.

The electrical property values (piezoelectric strain constant d ₃₃ , electromechanical coupling coefficient k ₃₃ ) of the obtained sample were measured based on a standardized measurement method of the Electronics Industry Association (EMAS). Further, the sample was heated, and the maximum value of the relative dielectric constant at the time of phase transition from the high temperature side paraelectric phase to the low temperature side ferroelectric phase was measured to obtain the Curie temperature Tc. Furthermore, a piezoelectric element was introduced into a reflow furnace (maximum temperature 250 ° C., set to 5 seconds), and when the deterioration rate of the piezoelectric d constant was within 3%, a value exceeding ○ 3% was marked with ×. The coercive electric field Ec of the piezoelectric actuator element having the composition range of the present invention was 0.7 kV / mm or more. Further, the crystal phase of PZT is a pattern that exists at 2θ = 43 to 46 ° after measuring the X-ray pattern with X-rays (CuKα1 characteristic X-ray, step width: 0.01671 °) using an XRD apparatus. The volume fraction was determined by separating the tetragonal, rhombohedral and orthorhombic peaks using Rietveld analysis. Here, for the obtained X-ray diffraction pattern, the tetragonal, monoclinic, and rhombohedral crystals of the crystal structure assumed when the constituent elements are used are assigned, and three types of crystals are distributed by Rietveld analysis. Asked. Tables 1 and 2 show the results.

In FIG. For 1, 3, 4, 5 and 24, the temperature dependence of the piezoelectric strain constant d ₃₃ was shown. As is apparent from FIG. 3 and Tables 1 and 2, in the piezoelectric ceramic of the present invention, the volume ratio of tetragonal crystal is 40% or more, the piezoelectric strain constant d ₃₃ is 400 × 10 ⁻¹² m / V or more, and the electric machine The coupling coefficient k ₃₃ is 68.3% or more, the Curie temperature Tc is 265 ° C. or more, and the decrease rate of the piezoelectric strain constant d ₃₃ is 3% or less even after the test using the reflow furnace (maximum temperature 250 ° C., 5 seconds). there were.

In particular, 0.03 ≦ x ≦ 0.05, 0.01 ≦ y ≦ 0.03, 0.071 ≦ a ≦ 0.08, 0.004 ≦ b ≦ 0.006, 0.44 ≦ c ≦ 0. Assuming 46, 0.4 mass% ≦ α ≦ 0.6 mass%, the piezoelectric strain constant d ₃₃ was 500 × 10 ⁻¹² or more and the heat resistance was good.

In contrast, if the samples outside the present invention is the piezoelectric strain constant _{d 33} is less than 400 × ^{10 -12} m / V, or reflow furnace (maximum temperature 250 ° C., 5 seconds) the piezoelectric strain constant _{d 33} after the test by The rate of decrease was greater than 3%. Sample No. In the samples 1, 3, 4 and 5, rhombohedral crystals were not confirmed, and monoclinic volume fractions were 56, 47, 40 and 36% by volume.

It is a fragmentary sectional view which shows the piezoelectric actuator element of this invention. It is a cross-sectional schematic diagram of the circuit module of the present invention. Sample No. of Example 1, 3, 4, 5 and is a graph showing the temperature dependence of the piezoelectric constant _{d 33} of about 24.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric layer 3 Internal electrode 11 Piezoelectric actuator element 13 Circuit board 15 Driving electrode

Claims (5)

Pb (Zr, Ti) O ₃ and Pb (Yb _1/2 M _1/2 ) O ₃ (where M is at least one of Nb or Sb) are the main components, and Sr (Zr, Ti) is the main component. Perovskite type in which at least three kinds of complex oxides selected from O ₃ , Ba (Zr, Ti) O ₃ , Pb (Ni _1/2 Te _1/2 ) O ₃ and Pb _1/2 NbO ₃ are dissolved. A piezoelectric ceramic composition comprising a composite oxide having a structure. The composition formula by the molar ratio of elements
_{Pb 1-x-y Sr x} Ba y (Yb 1/2 M 1/2) a (Ni 1/2 Te 1/2) b Zr c Ti 1-a-b-c O 3 + αPb 1/2 NbO 3 (Where M is at least one of Nb and Sb), x, y, a, b, c and α (mass%) are
0 ≦ x ≦ 0.08
0 ≦ y ≦ 0.08
0 <x + y
0.01 ≦ a ≦ 0.12
0 ≦ b ≦ 0.02
0.43 ≦ c ≦ 0.54
0 ≦ α ≦ 1.2
The piezoelectric ceramic composition according to claim 1, wherein: It is obtained by firing the piezoelectric ceramic composition according to claim 1 or 2 and contains Pb, Zr, Ti, Yb, M (wherein M is at least one of Nb or Sb) as an element, and a crystal phase is a perovskite structure. A piezoelectric ceramic having a tetragonal crystal ratio of 40% or more when all crystals are represented by a volume fraction. A piezoelectric actuator element comprising an electrode formed on a surface of the piezoelectric ceramic according to claim 3. A circuit module, wherein the piezoelectric actuator element according to claim 4 is surface-mounted on a circuit board.

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