JP2022107863A - Piezoelectric ceramic, piezoelectric element, and ultrasonic vibrator - Google Patents

Abstract

To provide a piezoelectric ceramic capable of forming a piezoelectric element that is small in both mechanical loss and electrical loss during its drive.SOLUTION: A piezoelectric ceramic comprises, as a main component, a compound containing Pb, Zr, Ti, Zn, Nb, Mn and O as constituent elements and having a Perovskite-based structure, with the contained particles having an average particle diameter ravg of 4 μm, wherein, in X-ray diffraction measurements using Cu-K α-rays, a total ratio ((IZT+IZnO)/IP×100) of a maximum peak intensity IZT expressed at 34.0°≤2θ≤35.0° and a maximum peak intensity IZnO expressed at 35.5°≤2θ≤37.0° with respect to a maximum peak intensity IP expressed at 20.0°≤2θ≤40.0° is 1.0% or smaller.SELECTED DRAWING: Figure 1

Description

The present invention relates to piezoelectric ceramics, piezoelectric elements, and manufacturing methods thereof.

Piezoelectric elements are used in sensor elements, power generating elements, and the like by utilizing the positive piezoelectric effect that converts mechanical energy into electrical energy. Piezoelectric elements are also used in vibrators, sound generators, actuators, ultrasonic motors, pumps, etc., by utilizing the inverse piezoelectric effect of converting electrical energy into mechanical energy. Furthermore, piezoelectric elements are also used in circuit elements, vibration control elements, etc., due to the combination of the positive piezoelectric effect and the inverse piezoelectric effect.

Among piezoelectric elements, piezoelectric transformers, vibrators, ultrasonic motors, and the like are continuously driven under conditions where large amplitudes such as resonance points occur, so the elements themselves tend to generate heat. Since the heat generation of the piezoelectric element leads to deterioration or loss of piezoelectric characteristics, it is necessary to suppress this. The heat generated by the piezoelectric element is caused by mechanical loss and electrical loss that occur during driving. For this reason, the above-described piezoelectric element is made of a material called a hard piezoelectric material or a hard material, which has a small loss in both cases. In hardware piezoelectric materials, a high mechanical quality factor Qm is important as an index of small mechanical loss, and a small dielectric loss tangent tan δ is important as an index of small electrical loss.

As such a low-loss hard piezoelectric material, lead zirconate titanate (Pb(Zr, Ti)O ₃ : PZT) having a perovskite structure is used as a basic composition, and various elements are dissolved therein. A low-loss type has been proposed.

For example, as a piezoelectric ceramic composition that has a high mechanical quality factor Qm and can be fired at a relatively low temperature, a compound containing Pb, Zn, Nb, Ti, Zr and O as constituent elements and having a perovskite structure is mainly used. A component is known (Patent Documents 1 and 2).

Japanese Patent Publication No. 54-18400 Japanese Patent Application Laid-Open No. 2001-181037

In a piezoelectric ceramic composition containing Pb, Zn, Nb, Ti, Zr and O as constituent elements and mainly composed of a compound having a perovskite structure, the addition of Mn results in a piezoelectric ceramic having a high mechanical quality factor Qm. A device is obtained. However, in this case, there is a problem that the dielectric loss tangent tan .delta. increases and the electrical loss increases.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a piezoelectric ceramic that enables a piezoelectric element to be obtained with small mechanical loss and small electrical loss during driving.

In the process of studying to solve the above problems, the inventors of the present invention have found that in a piezoelectric element having a large dielectric loss tangent tan δ formed of the piezoelectric ceramic composition described above, the sintered particles forming the piezoelectric ceramics have a particle size of It has been found that piezoelectric ceramics contain Zn-containing oxides that are large and have crystal structures other than the perovskite structure. Then, the present inventors have found that the above problems can be solved by using piezoelectric ceramics in which the generation of sintered particles having a large particle size and oxides containing Zn are suppressed, and have completed the present invention.

That is, one aspect of the present invention for solving the above problems includes Pb, Zr, Ti, Zn, Nb, Mn and O as constituent elements, and the molar ratio of Mn to Ti (Mn/Ti) is 0.07 and the average particle size r _avg of the particles contained is 4 μm or less, and 20.0°≦2θ in X-ray diffraction measurement using Cu—Kα rays. The maximum peak intensity I _ZT appearing at 34.0° ≤ 2θ ≤ 35.0° and the maximum peak intensity I appearing at 35.5° ≤ 2θ ≤ 37.0° for the maximum peak intensity I _P appearing at ≤ 40.0° Piezoelectric ceramics having a total ratio ((I _ZT +I _ZnO )/I _P ×100) with _ZnO of 1.0% or less.

Another aspect of the present invention is a piezoelectric element comprising the aforementioned piezoelectric ceramics and electrodes electrically connected to the piezoelectric ceramics.

Further, another aspect of the present invention is an ultrasonic transducer comprising the aforementioned piezoelectric element and a pair of block bodies sandwiching the piezoelectric element from one axial direction.

According to the present invention, it is possible to provide a piezoelectric ceramic that allows obtaining a piezoelectric element with small mechanical loss and small electrical loss during driving.

FIG. 1 is a schematic perspective view showing the structure of a laminated piezoelectric element according to one aspect of the present invention; FIG. 2 is a left side view of the laminated piezoelectric element shown in FIG. 1; A-A' cross-sectional view of the laminated piezoelectric element shown in FIG.

Hereinafter, with reference to the drawings, the configuration and effects of the present invention will be described along with technical ideas. However, the mechanism of action is presumed, and whether it is correct or not does not limit the present invention. It should be noted that the description of a numerical range (a description in which two numerical values are connected by "-") is meant to include numerical values described as lower and upper limits.

In this specification, "driving at high speed and large amplitude" of the piezoelectric element means driving at the resonance frequency, or driving under the condition that the vibration velocity measured with a laser Doppler vibrometer is 0.62 m / s or more. Say.

[Piezoelectric ceramics]
A piezoelectric ceramic according to one aspect of the present invention (hereinafter sometimes simply referred to as "first aspect") contains Pb, Zr, Ti, Zn, Nb, Mn and O as constituent elements, and Mn relative to Ti The molar ratio (Mn/Ti) of is 0.07 or less, the main component is a compound having a perovskite structure, the average particle size r _avg of the particles contained is 4 μm or less, and Cu-Kα radiation is used In the X _- ray diffraction measurement, the maximum peak intensity I _ZT appearing at 34.0° ≤ 2θ ≤ 35.0° and 35.5° ≤ The ratio of the total to the maximum peak intensity I _ZnO appearing at 2θ≦37.0° ((I _ZT +I _ZnO )/I _P ×100) is 1.0% or less.

The first side contains Pb, Zr, Ti, Zn, Nb, Mn and O as constituent elements, and is mainly composed of a compound having a perovskite structure. As a result, the compound having a perovskite structure is mainly composed of Pb(Zr, Ti)O ₃ —Pb(Zn, Nb)O ₃ —Pb(Mn, Nb)O ₃ . , a large amount of displacement can be obtained with respect to the applied voltage, and mechanical loss during driving can be suppressed.

The first aspect has a molar ratio of Mn to Ti contained as a constituent element (Mn/Ti) of 0.07 or less. As a result, the dielectric loss tangent tan δ becomes smaller when the piezoelectric element is formed, and the electrical loss during driving can be suppressed. The reason for this is not clear at present, but is presumed as follows. Mn is located at the same site (B site) as Ti and Zn in the perovskite structure. If the amount of Mn in the piezoelectric ceramic becomes too large, part of the contained Ti and Zn cannot exist in the perovskite structure, resulting in Zn _p Ti _q O _r (where p, q, and r are real numbers). ) and ZnO, which have crystal structures other than the perovskite structure. The presence of such oxides increases the dielectric loss tangent tan δ when the piezoelectric element is formed. On the other hand, when the molar ratio (Mn/Ti) is 0.07 or less, the generation of oxides having a crystal structure other than the perovskite structure is suppressed. It is kept low, and electrical loss during driving is small. The molar ratio (Mn/Ti) is preferably 0.05 or less in order to obtain a piezoelectric element with smaller electrical loss. Although the lower limit of the molar ratio (Mn/Ti) is not particularly limited, it is preferably 0.02 or more, more preferably 0.03 or more, in order to obtain a piezoelectric element with a high mechanical quality factor Qm. more preferred.

In the first aspect, it is preferable that the compositional formula is represented by the following formula (1) in that a larger amount of displacement and a lower mechanical loss can be achieved.

provided that a, b, x, y and z in the formula are respectively −0.05≦a≦0.05, 0.45≦b≦0.60, 0<x≦0.85, 0<y< It is a real number that satisfies 1.0, 0.01<z<0.10 and x+y+z=1.0.

Here, the first side surface contains Pb, Zr, Ti, Zn, Nb, Mn and O as constituent elements, contains a compound having a perovskite structure as a main component, and is represented by the above formula (1) It is confirmed by the following procedures that it has a composition and that the molar ratio (Mn/Ti) is 0.07 or less. First, a piezoelectric ceramic is pulverized to prepare a powdery sample. When piezoelectric ceramics form a piezoelectric element, it is preferable to pulverize after removing portions other than the piezoelectric ceramics, such as electrodes and coatings. In the case of a piezoelectric element which is difficult to separate from the portion and has a higher proportion of the piezoelectric ceramic portion than the other portions, the entire element may be pulverized to obtain a powdery sample. Next, for the obtained powdery sample, the diffraction line profile is measured with an X-ray diffractometer (XRD) using Cu-Kα rays, and the diffraction line intensity derived from other structures is compared with the strongest diffraction line intensity in the profile derived from the perovskite structure. When the ratio of the strongest diffraction line intensity in the profile is 10% or less, it is determined that the piezoelectric ceramic is mainly composed of a compound having a perovskite structure. In addition, when the piezoelectric element is pulverized into a powder sample without separating the piezoelectric ceramic portion from other portions, a peak clearly derived from a portion other than the piezoelectric ceramic, such as the electrode, in the diffraction line profile is observed, the peak is excluded and the strongest line intensity is compared as described above. Next, a powdery sample confirmed to contain a compound having a perovskite structure as a main component is subjected to high frequency inductively coupled plasma emission spectrometry (ICP), ion chromatography, or X-ray fluorescence spectrometry (XRF). do the analysis. Then, the presence or absence of each element other than oxygen is confirmed from the result of the composition analysis, and when the existence thereof is confirmed, it is determined that the piezoelectric ceramic contains each of the above elements. Further, from the result of the composition analysis, the content ratio of the elements other than oxygen is calculated, and the content ratio is the ratio in the above formula (1), so that the piezoelectric ceramic has the composition represented by the above formula (1). It is judged to have Furthermore, the molar ratio of Mn to Ti (Mn/Ti) is calculated from the result of composition analysis, and if this value is 0.07 or less, the molar ratio of Mn to Ti for piezoelectric ceramics of 0.07 or less ( Mn/Ti).

The first side surface may contain other additive elements or compounds as long as it contains the above elements as constituent elements and is mainly composed of a compound having a perovskite structure. Examples of additive elements include Ca, Sr, Ba, Ag, La, Ce, Bi, etc., which form a solid solution at the A site, Mg, Fe, Co, which form a solid solution at the B site, in the perovskite structure represented by _ABO3 . , Ni, Ta and W, and the like. Examples of the compound include a glassy grain boundary phase derived from a component added to lower the sintering temperature.

The first side is the maximum peak intensity I _P appearing at 20.0° ≤ 2θ ≤ 40.0° in X-ray diffraction measurement using Cu-Kα rays, at 34.0° ≤ 2θ ≤ 35.0° The ratio of the total of the maximum peak intensity I _ZT appearing and the maximum peak intensity I _ZnO appearing at 35.5 ° ≤ 2θ ≤ 37.0 ° ({(I _ZT + I _ZnO )/I _P } × 100) (hereinafter, “Zn oxide content”) is 1.0% or less. As a result, the piezoelectric element has a low dielectric loss tangent tan δ.

In the first aspect, when performing X-ray diffraction measurement using Cu—Kα rays, the maximum peak intensity I _P that appears in the range of 2θ from 20.0° to 40.0° is the perovskite type that is the main component It is derived from a compound having a structure. On the other hand, the maximum peak intensity I _ZT that appears in the range of 2θ from 34.0° to 35.0° is an oxide containing Zn and Ti (Zn _p Ti _q O _r (where p, q and r are real numbers) ), and the maximum peak I _ZnO appearing in the 2θ range of 35.5° to 37.0° is derived from zinc oxide (ZnO). Then, the small value of the Zn-containing oxide ratio, which is the ratio of the sum of _IZT and _IZnO to _IP , indicates that the content ratio of Zn-containing oxides having a crystal structure different from the perovskite structure is relatively high. means low. When this ratio is 1.0% or less, the increase in the dielectric loss tangent tan δ due to the Zn-containing oxide is suppressed, and a piezoelectric element having a low dielectric loss tangent tan δ can be obtained. From the viewpoint of obtaining a lower dielectric loss tangent tan δ, the Zn-containing oxide ratio is preferably low, preferably 0.5% or less, more preferably 0.3% or less, and less than 0.3% is more preferable.

Here, the Zn-containing oxide ratio is calculated by the following procedure. First, a piezoelectric ceramic is made into a powder sample by the method described above, and its XRD profile is measured. Next, the obtained results were analyzed using crystal structure analysis software (JADE, manufactured by Lightstone Co., Ltd.), and the maximum peak intensity IP at 20.0 ° ≤ 2θ ≤ _40.0 °, 34.0 ° Determine the maximum peak intensity I _ZT at ≦2θ≦35.0° and the maximum peak I _ZnO at 35.5°≦2θ≦37.0°, respectively. Finally, using the obtained I _P , I _ZT , and I _ZnO , a value of {(I _ZT +I _ZnO )/I _P }×100 is calculated and defined as the Zn-containing oxide ratio.

In the first aspect, the contained particles have an average particle size r _avg of 4.0 μm or less. As a result, the difference in particle size between the particles becomes small, and a low dielectric loss tangent tan δ can be obtained when the particles are used as a piezoelectric element. In addition, piezoelectric ceramics with a small average grain size _ravg are less likely to cause a decrease in the amount of displacement per unit volume even if the thickness of each layer is reduced when used as a laminated piezoelectric element, which will be described later. preferable. From this point of view, the average particle size r _avg is preferably 1.0 μm or less, more preferably 0.8 μm or less. Although the lower limit of the average grain size r _avg is not particularly limited, it is about 0.1 μm in piezoelectric ceramics obtained by a general manufacturing method. In general piezoelectric ceramics, crystal grains are grown sufficiently during firing to block open pores in many cases, and in this case, the average grain size r _avg of the contained grains is large. However, in the first aspect, by suppressing grain growth during firing, the piezoelectric ceramic can form a piezoelectric element having both a high mechanical quality factor Qm and a low dielectric loss tangent tan δ. One side is different from common piezoelectric ceramics.

In the first aspect, the coefficient of variation of the grain size of the contained particles, C.I. V. is preferably 40% or less. Coefficient of variation of particle size C.I. V. When the .di-elect cons. is small, the fine structure becomes more uniform, and the dielectric loss tangent tan .delta. decreases when the piezoelectric element is formed. coefficient of variation C.I. V. is more preferably 38% or less.

Here, the average grain size r _avg in the first aspect and the grain size variation coefficient C.V. V. is determined by the following procedure.
First, platinum is vapor-deposited on the surface of piezoelectric ceramics in order to impart electrical conductivity to prepare a sample for measurement. As for the piezoelectric ceramics in the piezoelectric element, if there is an exposed portion on the surface of the element, the exposed portion is coated with platinum to prepare a sample for measurement. If the piezoelectric ceramic is not exposed on the surface of the piezoelectric element, after exposing the piezoelectric ceramic portion by polishing, grinding, cutting, etching, etc., heat treatment (thermal treatment) is performed at a temperature of 900 to 960 ° C. After etching), platinum is vapor-deposited to obtain a sample for measurement. Next, the sample for measurement is observed with a scanning electron microscope (SEM), and 4 to 6 photographs are taken at a magnification of about 60 to 200 particles in the field of view. Next, the equivalent circle diameter of each particle is calculated by performing image processing on the photographed photograph. Next, from the obtained circle-equivalent diameter ri of each particle and the number _n of particles obtained by calculating this, the average particle diameter r _avg is calculated by the following formula (2), and is taken as the average particle diameter of the piezoelectric ceramic. . Then, the standard deviation s of the particle size is calculated from the obtained average particle size _ravg and the values of r _i and n described above by the following formula (3). Finally, the coefficient of variation C.V. is calculated from the obtained average particle size _ravg and standard deviation s using the following formula (4). V. is calculated, and this is used as the variation coefficient C. V. and

[Method for producing piezoelectric ceramics]
The piezoelectric ceramics according to the first aspect is produced by, for example, mixing powders of compounds containing one or more elements selected from Pb, Zr, Ti, Zn, Nb and Mn, and obtaining mixed powders containing the respective elements. calcining the mixed powder to obtain a calcined powder; forming the calcined powder into a predetermined shape to obtain a compact; and firing the compact. This manufacturing method will be described below.

The powder of the compound used as the raw material is not limited in composition and particle size as long as the piezoelectric ceramics according to the first aspect can be obtained by firing. The compound constituting the powder may contain additional elements other than the elements described above. Examples of compounds that can be used include PbO and _Pb3O4 as Pb _- containing compounds, ZrO2 as Zr-containing compounds, _TiO2 as Ti _- containing compounds, ZnO as Zn-containing compounds, and Nb-containing compounds. Examples of Mn-containing compounds include Nb ₂ O ₅ and the like, and examples of Mn-containing compounds include MnCO ₃ and the like.

The method of mixing the raw material powders is not particularly limited as long as the powders are uniformly mixed while preventing contamination of impurities, and either dry mixing or wet mixing may be employed. When wet mixing using a ball mill is employed, mixing may be performed for, for example, about 8 to 24 hours. In a general method for manufacturing piezoelectric ceramics, the Mn-containing compound is not added when the raw material powder is mixed, and a method of adding it to the powder after calcining, which will be described later, is commonly used. You may employ|adopt this method in manufacturing.

The calcining conditions for the mixed powder are not limited as long as each raw material reacts to obtain a calcined powder containing the perovskite compound represented by the above-described compositional formula as a main component. C. to 1000.degree. C. for 2 to 8 hours. If the firing temperature is too low or the firing time is too short, unreacted raw materials and intermediate products may remain. On the other hand, if the firing temperature is too high or the firing time is too long, there is a possibility that the compound with the desired composition may not be obtained due to volatilization of Pb or Zn, or the product may solidify and become difficult to crush. There is a risk that the productivity will decrease.

As a method for molding the calcined powder obtained by calcination, it is commonly used for molding ceramic powder, such as uniaxial pressure molding of powder, extrusion molding of clay containing powder, and cast molding of slurry in which powder is dispersed. The method used can be adopted.

Here, when the piezoelectric ceramic is obtained as the piezoelectric ceramic layer 10 of the laminated piezoelectric element 100 shown in FIGS. 1 to 3, the following molding method can be adopted.

First, the calcined powder is mixed with a binder or the like to form a slurry or clay, which is formed into a sheet to obtain a raw sheet containing the calcined powder. As a method for forming the sheet, commonly used methods such as a doctor blade method and an extrusion molding method can be employed.

Next, an electrode pattern that will become the internal electrode 20 after firing is formed on the raw sheet containing the calcined powder. The electrode pattern may be formed by a commonly used method, and a method of printing or applying a paste containing an electrode material is preferable in terms of cost. When forming an electrode pattern by printing or coating, powder (common material) or glass frit having the same composition and crystal structure as the fired piezoelectric ceramics is used in order to improve the adhesion strength to the fired piezoelectric ceramics. It may be contained in the paste.

As a laminated piezoelectric element having a structure different from that shown in FIGS. 1 to 3, there is also one in which internal electrodes are electrically connected to each other via through holes (vias) penetrating through the piezoelectric ceramic layers. When manufacturing a laminated piezoelectric element having such a structure, prior to the formation of the electrode pattern, through holes are formed in the obtained green sheet by punching or irradiation with a laser beam, and the electrode pattern is formed before and after the formation. to fill the through holes with an electrode material. The filling method is not particularly limited, but a method of printing a paste containing an electrode material is preferable in terms of cost.

Finally, a predetermined number of raw sheets having electrode patterns formed thereon are laminated and the sheets are adhered to each other to obtain a compact. Lamination and adhesion may be carried out by a commonly used method, and the method of thermocompression bonding raw sheets by the action of a binder is preferable from the viewpoint of cost.

After the binder is removed from the molded body obtained by the above procedure, the molded body is sintered to become the piezoelectric ceramics relating to the first side surface. The sintering conditions may be appropriately set in consideration of the sinterability of the calcined powder and the durability of the electrode material in the case where the compact is contained. When firing a compact containing copper (Cu) or nickel (Ni) as an electrode material, the firing atmosphere is preferably a reducing or inert atmosphere in order to prevent oxidation. An example of firing conditions for a compact containing neither copper (Cu) nor nickel (Ni) as an electrode material is 900° C. to 1200° C. for 1 hour to 5 hours in an air atmosphere. If the sintering temperature is too low or the sintering time is too short, densification will be insufficient, and there is a risk that piezoelectric ceramics with desired characteristics will not be obtained. On the other hand, if the firing temperature is too high or the firing time is too long, the volatilization of Pb and Zn may cause composition deviation, and the properties may deteriorate due to the formation of coarse particles. Moreover, when the compact contains an electrode material, there is a risk that the electrode material will melt or diffuse, making it impossible to obtain piezoelectric ceramics or piezoelectric elements with desired characteristics. It is preferable to set the firing temperature to 1100° C. or less in order to avoid such problems due to the firing temperature being too high and to reduce the material cost by using a low-melting-point material for the electrode material. When obtaining a plurality of piezoelectric ceramics or piezoelectric elements from one compact, the compact may be divided into several blocks prior to firing.

[Piezoelectric element]
A piezoelectric element according to another aspect of the present invention (hereinafter sometimes simply referred to as a “second aspect”) includes the piezoelectric ceramics according to the first aspect described above and the piezoelectric ceramics electrically connected to the piezoelectric element. and an electrode. Since the second side is provided with the piezoelectric ceramics related to the first side, it has a low dielectric loss tangent tan δ while maintaining a high mechanical quality factor Qm. becomes a piezoelectric element with less

In the second aspect, the material, shape and arrangement of the electrodes are not particularly limited as long as a desired voltage can be applied to the piezoelectric ceramics. Examples of electrode materials include silver (Ag), copper (Cu), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), and alloys thereof. Also, examples of the shape and arrangement of the electrodes include those that cover substantially the entire specific surface of the piezoelectric ceramics. In addition, when the piezoelectric element is a laminated piezoelectric element 100 having a layered structure of piezoelectric ceramic layers 10 and internal electrodes 20 as shown in FIGS. In addition to the external electrodes 30 for applying a voltage and taking out the voltage generated in the piezoelectric ceramic portion, it is provided with connecting conductors 31 and 32 that cover the exposed portions of the internal electrodes and connect them to every other layer. good too.

[Manufacturing method of piezoelectric element]
The piezoelectric element according to the second side surface is manufactured by forming electrodes on the surface of the piezoelectric ceramics according to the first side surface and subjecting it to polarization treatment. This manufacturing method will be described below.

For the formation of the electrodes, commonly used methods such as applying or printing a paste containing an electrode material to the surface of the piezoelectric ceramics and baking the paste, or vapor-depositing the electrode material on the surface of the piezoelectric ceramics can be employed.

Conditions for the polarization treatment are not particularly limited as long as the direction of spontaneous polarization can be aligned without causing damage such as cracks in the piezoelectric ceramics. An example is applying an electric field of 1 kV/mm to 5 kV/mm at a temperature of 100.degree. C. to 180.degree.

[Ultrasonic transducer]
An ultrasonic transducer according to still another aspect of the present invention (hereinafter sometimes simply referred to as a "third aspect") comprises a piezoelectric element according to the second aspect and a pair of piezoelectric elements sandwiching the piezoelectric element from one axial direction. and a block body of This ultrasonic transducer is known as a Langevin transducer. The Langevin vibrator may be a so-called bolt-tightened Langevin vibrator in which a block body is sandwiched between and integrated with a piezoelectric element by bolting. The Langevin vibrator operates to generate ultrasonic vibrations by supplying electric energy to a piezoelectric element and to transmit the ultrasonic vibrations to the outside through the block body. Since the third side includes the piezoelectric element related to the second side, the vibrator generates little heat when driven at high speed and large amplitude, and can be stably driven for a long period of time.

The material of the block used in the third aspect is not particularly limited as long as it can efficiently transmit ultrasonic vibrations generated from the piezoelectric element. For example, titanium alloy, aluminum alloy, SUS, or the like can be used.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples.

(Example 1)
[Manufacturing of piezoelectric ceramics]
As starting materials, high _- purity _Pb3O4 , ZrO2, _TiO2 , ZnO, _Nb2O5 and _MnCO3 powders _were prepared, and _each powder had a composition formula of Pb {Zr _0.4029 Ti _0.3871 (Zn _1/3 Nb _2/3 ) _0.18 (Mn _1/3 Nb _2/3 ) _0.03 } O ₃ Weighed so as to obtain a calcined powder having a perovskite structure, Wet mixing was carried out in a ball mill using zirconia balls. The Mn/Ti molar ratio in the composition formula is 0.022. After mixing, the mixed powder from which the dispersion medium was removed was calcined in the atmosphere at 820° C. for 3 hours to obtain calcined powder. After the obtained calcined powder was pulverized, the calcined powder was mixed with an acrylic binder and uniaxially press-molded under a load of 2 tf to obtain a disk-shaped compact having a diameter of 10 mm. The obtained molded body was fired at 1100° C. for 2 hours in the atmosphere to obtain the piezoelectric ceramics according to Example 1.

[Measurement of Zn-containing oxide ratio of piezoelectric ceramics]
When the Zn-containing oxide ratio of the obtained piezoelectric ceramics was measured and calculated by the method described above, the XRD profile was 34.0°≦2θ≦35.0° and 35.5°≦2θ≦37. No peak was observed in each range of 0°, and the Zn-containing oxide ratio was 0%.

[Measurement of average particle size and coefficient of variation of piezoelectric ceramics]
The average grain size r _avg and coefficient of variation C.V. V. was determined by the method described above, r _avg =0.70 μm, C.I. V. = 36.5%.

[Manufacture of test piezoelectric element]
An electrode was formed by applying Ag paste to both sides of the disk-shaped piezoelectric ceramics described above, and baking the ceramics by passing through a belt furnace set at 800°C.
After forming the electrodes, the piezoelectric ceramics were subjected to a polarization treatment in silicon oil at 150° C. for 15 minutes at an electric field strength of 2.2 kV/mm to obtain piezoelectric elements for testing.

[Dielectric loss tangent measurement of test piezoelectric element]
The dielectric loss tangent tan δ of the test piezoelectric element 24 hours after polarization was measured using an LCR meter under the conditions of a frequency of 1 kHz and an OSC of 1 V, and tan δ was 0.37%.

(Examples 2-3)
[Manufacturing of piezoelectric ceramics]
The composition formula of the calcined powder to be obtained is Pb{Zr _0.4029 Ti _0.3871 (Zn _1/3 Nb _2/3 ) _0.16 (Mn _1/3 Nb _2/3 ) _{0 .05} } O3 (Example 2), and Pb{ _{Zr0.4029Ti0.3871} ( _Zn1 / _{3Nb2 /3 ) 0.13} ( _Mn1 /3Nb2 _/3 ) _{0. 08} } O ₃ (Example 3), piezoelectric ceramics according to Examples 2 and 3 were produced in the same manner as in Example 1, respectively. The Mn/Ti molar ratio in each composition formula is 0.045 (Example 2) and 0.067 (Example 3), respectively.

[Measurement of Zn-containing oxide ratio, average particle size and coefficient of variation of piezoelectric ceramics]
When the Zn-containing oxide ratio of each of the obtained piezoelectric ceramics was measured and calculated in the same manner as in Example 1, the XRD profile of all piezoelectric ceramics was 34.0° ≤ 2θ ≤ 35.0. ° and 35.5°≦2θ≦37.0°, and the Zn-containing oxide ratio was 0%. Also, the average particle diameter r _avg and the coefficient of variation C.V. V. was measured and calculated in the same manner as in Example 1. In Example 2, r _avg =0.74 μm, C.I. V. =35.0%, and in Example 3, r _avg =0.79 μm, C.I. V. = 39.4%.

[Manufacturing of test piezoelectric element and measurement of dielectric loss tangent]
A test piezoelectric element was produced from each obtained piezoelectric ceramic in the same manner as in Example 1, and its dielectric loss tangent tan δ was measured. As a result, the test piezoelectric element according to Example 2 had tan δ=0.31%, and the test piezoelectric element according to Example 3 had tan δ=0.50%.

(Example 4)
[Manufacturing of piezoelectric ceramics]
Mixing and calcination are carried out by excluding the _MnCO3 powder from the raw material powder, and the resulting calcined powder is mixed with the same amount of _MnCO3 powder as the raw material powder in Example 2, and then molded. A piezoelectric ceramic according to Example 4 was manufactured in the same manner as in Example 2, except that this was done.

[Measurement of Zn-containing oxide ratio, average particle size and coefficient of variation of piezoelectric ceramics]
When the Zn-containing oxide rate of the obtained piezoelectric ceramics was measured and calculated in the same manner as in Example 1, it was 0.9%. Also, the average grain size r _avg and the coefficient of variation C.V. V. was measured and calculated in the same manner as in Example 1, r _avg =3.3 μm, C.I. V. = 39.7%.

[Manufacturing of test piezoelectric element and measurement of dielectric loss tangent]
A test piezoelectric element was manufactured from the obtained piezoelectric ceramics in the same manner as in Example 1, and its dielectric loss tangent tan δ was measured. As a result, tan δ was 0.63%.

(Comparative example 1)
[Manufacturing of piezoelectric ceramics]
Mixing and calcination are carried out by excluding the _MnCO3 powder from the raw material powder, and the same amount of MnCO3 powder as that blended as the raw material powder in Example ₃ is mixed with the obtained calcined powder, followed by molding. A piezoelectric ceramic according to Comparative Example 1 was manufactured in the same manner as in Example 3, except that this was done.

[Measurement of Zn-containing oxide ratio, average particle size and coefficient of variation of piezoelectric ceramics]
When the Zn-containing oxide ratio of the obtained piezoelectric ceramic was measured and calculated in the same manner as in Example 1, it was 1.6%. Also, the average grain size r _avg and the coefficient of variation C.V. V. was measured and calculated in the same manner as in Example 1, r _avg =4.5 μm, C.I. V. = 46.5%.

[Manufacturing of test piezoelectric element and measurement of dielectric loss tangent]
A test piezoelectric element was manufactured from the obtained piezoelectric ceramics in the same manner as in Example 1, and its dielectric loss tangent tan δ was measured. As a result, tan δ was 1.17%.

Table 1 summarizes the results of Examples and Comparative Examples.

Comparing the examples with the comparative examples, the piezoelectric ceramics according to the examples having a Zn-containing oxide ratio of 1.0% or less and an average particle size r _avg of 4 μm or less have the following characteristics when made into piezoelectric elements: It can be seen that it exhibits a low dielectric loss tangent tan δ. In addition, since the piezoelectric ceramics according to the examples and the comparative examples both contain Mn, they can be said to exhibit a high mechanical quality factor Qm when made into piezoelectric elements. In fact, it was confirmed that piezoelectric elements having a mechanical quality factor Qm exceeding 1500 can be obtained from the piezoelectric ceramics according to Example 3 and Comparative Example 1, which have the highest Mn content. Based on these facts, it contains Pb, Zr, Ti, Zn, Nb, Mn and O as constituent elements, is mainly composed of a compound having a perovskite structure, has a Zn-containing oxide rate of 1.0% or less, and Piezoelectric ceramics containing particles having an average particle size r _avg of 4 μm or less exhibit a high mechanical quality factor Qm and a low dielectric loss tangent tan δ, and are piezoelectric elements with small mechanical loss and small electrical loss during driving. It can be said that it can be obtained.

In addition, when comparing Examples 2 and 3 in which MnCO ₃ , which is a Mn-containing compound, was mixed with the raw material powder at the time of production, and Example 4 and Comparative Example 1 in which this was mixed with the calcined powder, the former was better. , it has a low Zn-containing oxide ratio and a small average grain size _ravg at the same Mn content, and a smaller dielectric loss tangent tan δ can be obtained when it is made into a piezoelectric element. Therefore, when it is necessary to contain a large amount of Mn in the piezoelectric ceramics in order to obtain a piezoelectric element with a high mechanical quality factor Qm, a Mn-containing compound is mixed with the raw material powder and calcined. , it can be said that the deterioration of the dielectric loss tangent tan δ can be suppressed.

According to the present invention, it is possible to provide a piezoelectric ceramic that allows obtaining a piezoelectric element with small mechanical loss and small electrical loss during driving. Such piezoelectric ceramics produce less heat than conventional ones when driven at high speed and large amplitude by forming ultrasonic vibrators, piezoelectric transformers, etc., and have high performance and high reliability. becomes. Therefore, the piezoelectric element provided with the piezoelectric ceramics according to the present invention can be suitably used for ultrasonic transducers, piezoelectric transformers, and the like.

100 Laminated piezoelectric element 10 Piezoelectric ceramic layer 20 Internal electrode 30 External electrodes 31, 32 Connection conductor

Claims (7)

Containing Pb, Zr, Ti, Zn, Nb, Mn and O as constituent elements,
The molar ratio of Mn to Ti (Mn/Ti) is 0.07 or less,
The main component is a compound having a perovskite structure,
The average particle diameter r _avg of the particles contained is 4 μm or less, and the maximum peak intensity IP appearing at 20.0 ° ≤ 2θ ≤ 40.0 ° in X _- ray diffraction measurement using Cu-Kα rays, 34 The total ratio of the maximum peak intensity I _ZT appearing at 0° ≤ 2θ ≤ 35.0° and the maximum peak intensity I _ZnO appearing at 35.5° ≤ 2θ ≤ 37.0° ((I _ZT + I _ZnO )/I _P ×100) is 1.0% or less. 2. The piezoelectric ceramics according to claim 1, wherein the compositional formula is represented by the following formula (1).

(where a, b, x, y and z in the formula are -0.05 ≤ a ≤ 0.05, 0.45 ≤ b ≤ 0.60, 0 < x ≤ 0.85, 0 < y Real numbers that satisfy <1.0, 0.01<z<0.10, and x+y+z=1.0.) 3. The piezoelectric ceramics according to claim 1, wherein the molar ratio of Mn to Ti (Mn/Ti) is 0.05 or less. The piezoelectric ceramics according to any one of claims 1 to 3, wherein said average grain size r _avg is 1.0 µm or less. The coefficient of variation of the particle size of the contained particles C.I. V. The piezoelectric ceramics according to any one of claims 1 to 4, wherein the is 40% or less. A piezoelectric element comprising the piezoelectric ceramic according to any one of claims 1 to 5 and an electrode electrically connected to the piezoelectric ceramic. 7. An ultrasonic transducer comprising the piezoelectric element according to claim 6 and a pair of block bodies sandwiching the piezoelectric element from one axial direction.

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