JPH1093154A - Piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress depolarization, to improve lack of polarization and to improve an electromechanical coupling coefficient by setting the electrode- forming face of a piezoelectric body to be a 100} face and the cutting face of the piezoelectric body to be the 100} face or a 110} face. SOLUTION: In the piezoelectric body 1 which is cut from a perovskite lead composite oxide crystal, the electrode-forming face is set to be the 100} face and the cutting face of the piezoelectric body 1 is formed to become the 100} face or the 110} face. The 100} face means the (100) face, a (010) face and the like, and the 110} face means a (110) face, a (101) face, a (011) face and the like. A first electrode 3 is formed along the side and a part of a face opposite to a transmitting/receiving face from the ultrasonic transmitting/receiving face of the piezoelectric body 1. A second electrode 4 is formed on the opposite face of the transmitting/receiving face. A piezoelectric element is formed by the piezoelectric body 1, the first electrode 3 and the second electrode 4. The plural piezoelectric elements are adhered on a packing, so that they are mutually detached and a ultrasonic probe is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element used for an ultrasonic diagnostic apparatus, an ultrasonic flaw detector and the like.

[0002]

2. Description of the Related Art An ultrasonic probe used for an ultrasonic diagnostic apparatus or an ultrasonic flaw detector is mainly composed of a piezoelectric element, irradiates an ultrasonic wave toward an object, and obtains an acoustic impedance of the object. By receiving reflected echoes from different interfaces, the internal state of the object can be imaged. Conventionally, as a piezoelectric element, lead zirconate titanate having a large dielectric constant and having a large electromechanical coupling coefficient (k ₃₃ ′, kt, etc.) and a large dielectric constant which is easy to match with a transmission / reception circuit having a small loss due to a cable or device stray capacitance (PZT) -based ceramics are used.

At present, an ultrasonic probe has a thickness of several tens μm.
An array probe in which tens to hundreds of strip-shaped piezoelectric elements of up to several hundreds of μm are arranged is mainstream, and the number of piezoelectric elements tends to increase with the demand for higher resolution. Also,
Improvements in the piezoelectric characteristics of the piezoelectric element itself are also required in response to demands for higher sensitivity and higher bandwidth of the ultrasonic probe. For these demands, P with a large electromechanical coupling coefficient
_{b [(Zn 1/3 Nb 2/3)} 1-x Ti x] O 3 ( where
x represents 0.05 ≦ x ≦ 0.20), Pb [(Mg
_1/3 Nb _2/3 ) _1-y Ti _y ] O ₃ (where y is 0.2
0 ≦ y ≦ 0.40), Pb [(Ni _1/3 Nb
_{2/3) 1-z Ti z]} O 3 ( however, z is 0.30 ≦ z ≦
0.50), Pb [(Co _1/3 Nb _2/3 ) _1-u T
i _u ] O ₃ (where u represents 0.10 ≦ u ≦ 0.30), Pb [(A _1/2 Nb _1/2 ) _1-w Ti _w ] O ₃ (where A is Sc, One kind selected from In, Fe, Y and rare earth elements, w represents 0.30 ≦ w ≦ 0.50), a complex oxide containing a divalent or trivalent metal element, and the like. An ultrasonic probe using a perovskite-type oxide single crystal such as a composite oxide of tantalate-lead titanate in which a part of Nb is replaced with Ta and a composite oxide obtained by combining these as a piezoelectric material is expected. . For example, lead zinc niobate Pb (Zn _1/3 Nb)
_2/3 ) The solid solution single crystal of O ₃ -lead titanate PbTiO _{3 has} a large electromechanical coupling coefficient (k ₃₃ ′) of 85 to 90%, which is larger than that of k ₃₃ ′ of the PZT piezoelectric ceramic by 70%. It is known that the characteristics are excellent. When this single crystal is used, the piezoelectric element can be made thin even at a low frequency at which a high-sensitivity signal can be obtained. Further, in cutting for manufacturing a strip-shaped piezoelectric element, the cutting depth of the blade of the dicing machine can be made shallow, and even a thin blade can be cut vertically, so that the production yield can be improved. Moreover, an ultrasonic probe with reduced side lobes can be provided. Further, since the relative dielectric constant is equal to or higher than that of the conventional PZT-based piezoelectric ceramic, matching with the transmission / reception circuit is improved, and a highly sensitive signal with reduced loss due to cables and stray capacitance of the device can be obtained. In particular, an ultrasonic probe including a piezoelectric element using a single crystal having a composition in which the molar fraction of lead titanate is 20% or less in the solid solution as a piezoelectric material is an ultrasonic probe using a conventional PZT-based piezoelectric ceramic as a piezoelectric material. A high-sensitivity signal that is 6 dB or more larger than that of the acoustic probe can be obtained. For this reason, in the case of the B-mode image, a high-resolution image is obtained in which small lesions and voids due to physical changes can be clearly seen to the deep part. In the case of the Doppler mode in which a CFM image or the like can be obtained, the diameter is several μm.
A reflected echo from a minute blood cell of about m can be obtained as a large signal.

A piezoelectric material used for a piezoelectric element of an ultrasonic probe is a plate having a size of 10 mm square or more, has a larger electromechanical coupling coefficient and a higher dielectric constant, and has an individual piezoelectric material. It is desired that the element has uniform characteristics of piezoelectric and dielectric materials. In the method of growing a single crystal by the Bridgman method, the composition fluctuation can be suppressed to a level at which there is no problem in practical use. As described above, in the case of manufacturing an ultrasonic probe driven at a low frequency using the piezoelectric body made of a single crystal as described above, a thin single crystal can be used, and a strip-shaped piezoelectric element with high dimensional accuracy can be manufactured using a thin blade. Possible to improve production yield,
Higher sensitivity and reduced side lobes are now possible.

[0005] However, among the ultrasonic probes manufactured by the above-mentioned method, there are cases in which the signal level is low and a high-resolution image cannot be obtained. The value of the electromechanical coupling coefficient (k ₃₃ ′) of the piezoelectric element constituting the low-sensitivity ultrasonic probe is lower than the initial value, and this decrease in k ₃₃ ′ causes the signal level to decrease. A piezoelectric element having a piezoelectric single crystal with a small signal level does not exhibit the original electromechanical coupling coefficient (k ₃₃ ′) of the piezoelectric single crystal because it is depolarized or insufficiently polarized. As described above, when the ultrasonic probe is manufactured, when the piezoelectric body of the strip-shaped piezoelectric element is depolarized or insufficiently polarized, there is a problem that the sensitivity is substantially reduced or the band is narrowed. . Therefore, although the above-mentioned perovskite oxide single crystal has an excellent electromechanical coupling coefficient, it has been difficult to mass-produce an ultrasonic probe from this single crystal.

[0006]

For example, Pb [(Zn
_{1/3 Nb 2/3) 1-x Ti} x] O 3 ( here, x is 0.0
When a single crystal of a perovskite-type lead composite oxide (such as 5 ≦ x ≦ 0.20) is used as a piezoelectric body of an ultrasonic probe, unlike a conventional PZT-based piezoelectric ceramic, electric power is generated when cutting or forming electrodes. The value of the mechanical coupling coefficient varies or falls below the original value. For this reason, the conventional P
There has been a problem that only the same sensitivity as that of an ultrasonic probe using a ZT-based piezoelectric ceramic can be obtained, or the performance of the ultrasonic probe varies. An object of the present invention is to provide a piezoelectric element having a high electromechanical coupling coefficient in which depolarization is suppressed and polarization insufficiency is improved.

[0007]

According to the present invention, there is provided a piezoelectric element in which an electrode is formed on a piezoelectric body having a cut surface cut from a perovskite-type lead composite oxide single crystal. The plane is a {100} plane, and the cut surface of the piezoelectric body is a {100} plane or a {1} plane.
It is characterized by a 10-degree plane.

Here, the {100} plane is the (100) plane,
(010) plane, (001) plane, (-100) plane, (0-
10) plane and (00-1) plane. Also, $ 11
The 0 ° plane is (110) plane, (101) plane, (011) plane
Plane, (-1-10) plane, (-10-1) plane, (0-1-
1) plane, (-110) plane, (-101) plane, (0-1) plane
1) plane, (1-10) plane, (10-1) plane, (01-
1) Mean plane.

According to the present invention, the electrode forming surface of the piezoelectric body made of a perovskite-type lead composite oxide single crystal is {100}, and the cut surface of the piezoelectric body is {10}.
Since the depolarization can be suppressed or prevented by setting the plane to {0} or {110}, a piezoelectric element having a high electromechanical coupling coefficient can be obtained. Such a piezoelectric element has, for example, an electromechanical coupling coefficient (k ₃₃ ′) of 85% or more and a small variation between the individual piezoelectric elements, but the piezoelectric element whose cut surface deviates from the {100} plane or the {110} plane. In a piezoelectric element having a body, the electromechanical coupling coefficient (k ₃₃ ′) is 80
%, The variation among the individual piezoelectric elements also increases.

When the perovskite-type lead composite oxide single crystal is used, the piezoelectric element can be made thin even at a low frequency at which a high-sensitivity signal can be obtained. Further, in cutting for manufacturing a strip-shaped piezoelectric element, the cutting depth of the blade of the dicing machine can be made shallow, and even a thin blade can be cut vertically, so that the production yield can be improved. Moreover, an ultrasonic probe with reduced side lobes can be provided. Further, since the relative dielectric constant is equal to or higher than that of the conventional PZT-based piezoelectric ceramic, matching with the transmission / reception circuit is improved, and a highly sensitive signal with reduced loss due to cables and stray capacitance of the device can be obtained.

Therefore, the electrode forming surface of the piezoelectric body is reduced by $ 10.
0} plane, and by setting the cut surface of the piezoelectric body to {100} plane or {110} plane, high sensitivity and wide band without impairing the original piezoelectric characteristics of the perovskite type lead composite oxide single crystal. An ultrasonic probe can be realized.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a piezoelectric element according to the present invention will be described in detail. This piezoelectric element has a structure in which an electrode is formed on a piezoelectric body having a cut surface cut from a perovskite-type lead composite oxide single crystal, and the electrode forming surface of the piezoelectric body is a {100} plane, and the piezoelectric body is Cut surface is $ 10
It has a calibration of 0 or {110} plane.

The perovskite-type lead composite oxide single crystal is, for example, Pb [(Zn _1/3 Nb _2/3 ) _1-x Ti _x ] O
₃ (where x indicates 0.05 ≦ x ≦ 0.20), P
b [(Mg _1/3 Nb _2/3 ) _1-y Ti _y ] O ₃ (However,
y represents 0.20 ≦ y ≦ 0.40), Pb [(Ni
_{1/3 Nb 2/3) 1-z Ti} z] O 3 ( however, z is 0.3
0 ≦ z ≦ 0.50), Pb [(Co _1/3 Nb
_2/3 ) _1-u Ti _u ] O ₃ (where u is 0.10 ≦ u ≦
0.30), Pb [(A _1/2 Nb _1/2 ) _1-w Ti
_w ] O ₃ (where A is one selected from Sc, In, Fe, Y and rare earth elements, w is 0.30 ≦ w ≦ 0.5
0) or P in the above formula
a composition in which a part of b is substituted with at least one of Na, Sr, Ca, and La in an amount of 10 mol% or less, or a composition in which a part of Nb in the above formula is substituted with Ta. preferable.

Preferably, the perovskite-type lead composite oxide single crystal exhibits a rhombohedral crystal at a temperature of 100 ° C. or less. The thickness (t) of the single-crystal piezoelectric body is 0.05
It is preferable that mm ≦ t ≦ 0.50 mm.

The electrode is not particularly limited as long as it is a conductive material. For example, Ti / Au (Ti; 10 to 50 n) is used.
m, Au 100 to 1000 nm) electrode, Cr / Au (C
r; 10 to 50 nm, Au; 100 to 1000 nm). These electrodes are formed by a sputtering method, a vapor deposition method, a coating method, or the like.

Next, an ultrasonic probe (array type ultrasonic probe) including the piezoelectric element according to the present invention will be described in detail with reference to FIG. A plurality of piezoelectric bodies 1 made of a perovskite-type lead composite oxide single crystal are separately bonded on a backing material 2. Each of the piezoelectric bodies 1 vibrates in the direction of arrow A in the figure. The first electrode 3 is formed from the ultrasonic transmitting and receiving surface of each of the piezoelectric bodies 1 to a side surface thereof and a part of a surface opposite to the transmitting and receiving surface. The second electrode 4 is formed on a surface of each of the piezoelectric bodies 1 opposite to the transmission / reception surface at a desired distance from the first electrode 3. The piezoelectric element 1 and the first and second electrodes 3 and 4 constitute a piezoelectric element (ultrasonic transmitting / receiving element). An acoustic matching layer 5 is formed on each of the ultrasonic transmitting and receiving surfaces of each of the piezoelectric bodies 1 including each of the first electrodes 3. The acoustic lens 6 is formed over the entire acoustic matching layer 5. The flexible printed wiring board 7 is connected to each of the first electrodes 3. The ground electrode plate 8 is connected to each of the second electrodes 4 by, for example, soldering. A plurality of conductors (cables) not shown are connected to the flexible printed wiring board 7 and the ground electrode plate 8, respectively.

The ultrasonic probe having the structure shown in FIG. 1 is manufactured by, for example, the following method. First,
A conductive film is deposited by sputtering on a perovskite-type lead composite oxide single crystal piece having a rectangular parallelepiped shape, and the conductive film is left on the ultrasonic transmitting / receiving surface and the surface opposite to the transmitting / receiving surface by a selective etching technique. Subsequently, an acoustic matching layer is formed on the surface of the single crystal piece that will be the ultrasonic transmitting / receiving surface, and these are adhered onto the backing material 2. Subsequently, the first and second cuts are made on the backing material 2 by cutting a plurality of times from the acoustic matching layer to the single crystal piece using a blade.
A plurality of separated piezoelectric bodies 1 having second electrodes 3 and 4 and a plurality of acoustic matching layers 5 arranged on the respective piezoelectric bodies 1 are formed. At this time, as shown in FIG. 2, the electrode forming surface of the piezoelectric body 1 shows a {100} plane, for example, a (001) plane and a (00-1) plane, and the cut plane is a {10} plane.
0 ° plane, for example, (100) plane, (-100) plane.

Next, after an acoustic lens 6 is formed on the acoustic matching layer 5, a flexible printed wiring board 7 is connected to each of the first electrodes 3, and an earth electrode plate 8 is attached to the second electrode 4 by, for example, soldering. Then, an ultrasonic probe is manufactured by connecting a plurality of conductors (cables) (not shown) to the flexible printed wiring board 7 and the ground electrode plate 8, respectively.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. (Example 1) First, PbO, Z having a purity of 99.9% or more
The molar ratio of nO, Nb ₂ O ₅ and TiO ₂ to lead zinc niobate (Pb [Zn _1/3 Nb _2/3 ] O ₃ ; abbreviated as PZN) and lead titanate (PbTiO ₃ ; abbreviated as PT) Is 9
1: 9 (that is, Pb [(Zn _1/3 Nb _2/3 ) _1-x Ti
_x] abbreviated as _{O 3, x = 0.09,91PZN-9PT} )
And the same amount of lead oxide (PbO) was added as a flux to the weighed material. Pure water was added to these powders and mixed for 1 hour in a ball mill using a zirconia ball. The mixture was dried, sufficiently mixed and pulverized by a raikai machine, and then placed in a rubber container and formed by isostatic pressing at a pressure of 2 ton / cm ² . This lump 1100
g in a 250 cc cylindrical platinum container with a bottom, and the container is further placed in an electric furnace, heated to a temperature of 1250 ° C. for 5 hours, and then gradually cooled to 800 ° C. at a cooling rate of 0.8 ° C./hr. Then, it was gradually cooled to room temperature. Subsequently, the platinum container was boiled with 20% nitric acid for 8 hours to dissolve the flux and take out crystals.

The obtained single crystal is about 40 mm square × 30 m
It was a substantially rectangular parallelepiped block of mL. The crystal structure was examined by an X-ray diffraction method, and the composition was analyzed by ICP. As a result, it has a rhombohedral perovskite structure at room temperature and Pb [(Zn _1/3 Nb _2/3 ) _1-x Ti _x ] O ₃
, X is 0.89 to 0.91.

Next, an <100> azimuthal axis was set for the obtained single crystal using an X-ray Laue camera, and a {100} plane single crystal piece having a thickness of 0.8 mm was cut out by slicing perpendicular to this axis. . Further, the whole surface was cut out so as to be a {100} surface and the plane size was 11 mm × 22 mm.
Subsequently, the {100} plane of the single crystal piece was polished with # 2000 abrasive grains to finish to a thickness of 0.3 mm. Subsequently, a Ti / Au electrode was formed on both surfaces {100} of the single crystal piece by sputtering, and an electric field of 1 kV / mm was applied in an insulating oil at 150 to 250 ° C. for 30 minutes, followed by electric field cooling and polarization. Done. The capacitance and the resonance and antiresonance frequencies were measured. As a result, the relative dielectric constant is 2200, the sound speed is 2850 m / s, and the electromechanical coupling coefficient k ₃₃ ′ is 85 to 87.
%.

Further, FIG. 1 described above using the single crystal is used.
The array type ultrasonic probe shown in FIG. That is,
The 91PZT-9PT piezoelectric single crystal was processed to a thickness of 2
A 50 μm square plate was produced. A Ti / Au conductor film is deposited on the upper and lower surfaces and side surfaces of the obtained square plate by a sputtering method,
By the selective etching technique, a part of the conductive film located on one side surface of the square plate and a part of the conductive film located on a surface opposite to a surface to be an ultrasonic transmitting / receiving surface were removed. Subsequently, an acoustic matching layer was formed on the surface of the square plate that would be an ultrasonic transmitting / receiving surface, and these were adhered onto the backing material 2. Subsequently, a 30 μm-thick diamond blade was used to cut the acoustic matching layer from the acoustic matching layer over the square plate, and cut into 190 μm-pitch strips. By this cutting, the first and second electrodes 3 on the backing material 2
In this manner, 100 separated piezoelectric bodies 1 each having a plurality of piezoelectric elements 4 and a plurality of acoustic matching layers 5 disposed on the respective piezoelectric bodies 1 were formed. As shown in FIG. 2, the piezoelectric body 1 has the (001) plane and the (00-1) plane on which the electrode is formed, and the (100) plane and the (-100) plane facing each other.

Next, after an acoustic lens 6 is formed on the acoustic matching layer 5, a flexible printed wiring board 7 is connected to each of the first electrodes 3 by soldering, and an earth electrode plate 8 is connected to each of the second electrodes 4 1 by soldering, and by connecting a plurality of conductors (cables) (not shown) each having a length of 110 mF / m and a length of 2 m to the flexible printed wiring board 7 and the ground electrode plate 8, respectively. An ultrasonic probe was manufactured.

With respect to the obtained array type ultrasonic probe, the reflection echo was measured by the pulse echo method. As a result, an echo having a center frequency of 2.5 MHz was obtained over all the elements.

Example 2 First, PbO, ZnO, Nb ₂ O ₅ and TiO ₂ having a purity of 99.9% or more were converted to lead zinc niobate (Pb [Zn _1/3 Nb _2/3 ] O ₃ ; PZN
) And lead titanate (PbTiO ₃ ; abbreviated as PT) in a molar ratio of 91: 9 (that is, Pb [(Zn _1/3 Nb _2/3 )).
_1-x Ti _x ] O ₃ , x = 0.09, 91PZN-9PT
), And the same amount of lead oxide (PbO) was added as a flux to the weighed material. Pure water was added to these powders and mixed for 1 hour in a ball mill using a zirconia ball. This mixture was dried and thoroughly mixed and pulverized with a raikai machine, and then placed in a rubber container and placed at 2 ton / cm.
It was formed by isostatic pressing at a pressure of ² . 1100 g of this lump is placed in a 250 cc cylindrical platinum container with a bottom,
Further, the vessel was placed in an electric furnace, heated to a temperature of 1250 ° C. for 5 hours, and then cooled at a cooling rate of 0.8 ° C./hr.
C., and then gradually cooled to room temperature. Subsequently, the platinum container was boiled with 20% nitric acid for 8 hours to dissolve the flux and take out crystals.

The obtained single crystal is about 40 mm square × 35 m
It was a substantially rectangular parallelepiped block of mL. The crystal structure was examined by an X-ray diffraction method, and the composition was analyzed by ICP. As a result, it has a rhombohedral perovskite structure at room temperature and Pb [(Zn _1/3 Nb _2/3 ) _1-x Ti _x ] O ₃
, X is 0.89 to 0.91.

Next, an <100> azimuthal axis was set for the obtained single crystal using an X-ray Laue camera, and sliced perpendicularly to this axis to cut out a {100} plane single crystal piece having a thickness of 0.4 mm. . In addition, the other two aspects are {110}
It was cut out so as to have a plane size of 11 mm × 22 mm. Subsequently, the {100} plane of the single crystal piece was #
It was polished with 2000 abrasive grains and finished to a thickness of 0.22 mm. Subsequently, Ti / Au electrodes were formed on both surfaces {100} surfaces of the single crystal piece by a sputtering method.
An electric field of 1 kV / mm was applied in an insulating oil at 50 ° C. for 30 minutes and then cooled by electric field to perform polarization. The capacitance and the resonance and antiresonance frequencies were measured. As a result, the relative dielectric constant becomes 2
100, sound speed 2800 m / s, electromechanical coupling coefficient k ₃₃ ′
Was found to be 88-89%.

Further, the above-described single crystal shown in FIG.
The array type ultrasonic probe shown in FIG. That is,
The 91PZT-9PT piezoelectric single crystal was processed to a thickness of 2
A 20 μm square plate was produced. A Ti / Au conductor film is deposited on the upper and lower surfaces and side surfaces of the obtained square plate by a sputtering method,
By the selective etching technique, a part of the conductive film located on one side surface of the square plate and a part of the conductive film located on a surface opposite to a surface to be an ultrasonic transmitting / receiving surface were removed. Subsequently, an acoustic matching layer was formed on the surface of the square plate that would be an ultrasonic transmitting / receiving surface, and these were adhered onto the backing material 2. Subsequently, using a diamond blade having a thickness of 25 μm, the acoustic matching layer was cut across the square plate, and cut into 200 μm pitch strips. By this cutting, the first and second electrodes 3 on the backing material 2
In this manner, 100 separated piezoelectric bodies 1 each having a plurality of piezoelectric elements 4 and a plurality of acoustic matching layers 5 disposed on the respective piezoelectric bodies 1 were formed. As shown in FIG. 2, the piezoelectric body 1 has a (001) plane and a (00-1) plane on which an electrode is formed, and a (110) plane and a (-1-10) plane. Was.

Next, after the acoustic lens 6 is formed on the acoustic matching layer 5, the flexible printed wiring board 7 is connected to each of the first electrodes 3 by soldering, and the ground electrode plate 8 is connected to each of the second electrodes 4. 1 by soldering, and by connecting a plurality of conductors (cables) (not shown) each having a length of 110 mF / m and a length of 2 m to the flexible printed wiring board 7 and the ground electrode plate 8, respectively. An ultrasonic probe was manufactured.

With respect to the obtained array type ultrasonic probe, the reflection echo was measured by the pulse echo method. As a result, an echo having a center frequency of 2.5 MHz was obtained over all the elements.

(Comparative Example 1) An <100> azimuthal axis was determined for the same single crystal as in Example 2 using an X-ray Laue camera, and sliced perpendicularly to this axis to form a 0.4 mm thick # 1.
A single crystal piece of the 00 ° plane was cut out. Further, the other two side surfaces are shifted by 10 ° from the {100} surface so that 11
It was cut out into a rectangular shape of mm × 22 mm. Subsequently, the {100} face of the single crystal piece was polished with # 2000 abrasive to finish to a thickness of 0.25 mm. Subsequently, a Ti / Au electrode was formed on both surfaces {100} of the single crystal piece by sputtering, and the Ti / Au electrode was formed in an insulating oil at 150 to 250 ° C.
After applying an electric field of kV / mm for 30 minutes, the electric field was cooled and polarization was performed. The capacitance and the resonance and antiresonance frequencies were measured. As a result, the relative dielectric constant was 2300 to 2600, and the sound velocity was 2
800 to 3000 m / s, the electromechanical coupling coefficient k ₃₃ ′ is 6
At 5 to 77%, it was confirmed that k ₃₃ ′ was small and each characteristic value also varied.

Further, FIG. 1 described above using the single crystal is used.
The array type ultrasonic probe shown in FIG. That is,
The 91PZT-9PT piezoelectric single crystal was processed to a thickness of 2
A 50 μm square plate was produced. A Ti / Au conductor film is deposited on the upper and lower surfaces and side surfaces of the obtained square plate by a sputtering method,
By the selective etching technique, a part of the conductive film located on one side surface of the square plate and a part of the conductive film located on a surface opposite to a surface to be an ultrasonic transmitting / receiving surface were removed. Subsequently, an acoustic matching layer was formed on the surface of the square plate that would be an ultrasonic transmitting / receiving surface, and these were adhered onto the backing material 2. Subsequently, using a diamond blade having a thickness of 25 μm, the acoustic matching layer was cut across the square plate, and cut into 200 μm pitch strips. By this cutting, the first and second electrodes 3 on the backing material 2
In this manner, 100 separated piezoelectric bodies 1 each having a plurality of piezoelectric elements 4 and a plurality of acoustic matching layers 5 disposed on the respective piezoelectric bodies 1 were formed. In the piezoelectric body 1, the electrode forming surface indicates the (001) plane and the (00-1) plane, and the opposing cut planes are 10 planes from the (110) plane and the (-1-10) plane, respectively.
゜ It was out of alignment. Further, after the cutting, the cut portion was observed with a microscope from the upper surface and the side surface. As a result, meandering and oblique cuts were not recognized, but some cracks and chips were partially recognized.

Next, after the acoustic lens 6 is formed on the acoustic matching layer 5, the flexible printed wiring board 7 is connected to each of the first electrodes 3 by soldering, and the ground electrode plate 8 is connected to each of the second electrodes 4 1 by soldering, and by connecting a plurality of conductors (cables) (not shown) each having a length of 110 mF / m and a length of 2 m to the flexible printed wiring board 7 and the ground electrode plate 8, respectively. An ultrasonic probe was manufactured.

With respect to the obtained array type ultrasonic probe, the reflection echo was measured by the pulse echo method. As a result, echoes having a center frequency of 2.5 MHz
Only 0% was found. When the impedance characteristics after being cut into strips were measured, 10% of the elements were defective. The sensitivity of the element from which the echo was obtained was 1 dB higher than that of the conventional PZT piezoelectric ceramic, but the sensitivity was 3 to 4 dB lower than those of Examples 1 and 2, and the sensitivity variation was as large as 3 dB at maximum in the array element. As a result, the frequency band is also -6.
It was confirmed that the average value of the fractional band was as narrow as 80% in dB.

Further, sound field measurements were performed on the ultrasonic probes of Examples 1 and 2 and Comparative Example 1, and the side lobe level when the beam was deflected by 60 ° by controlling the delay time of the applied pulse was examined. . As a result, the ultrasonic probes of Examples 1 and 2 were 4 times as compared with the ultrasonic probe of Comparative Example 1.
The dB side lobe level was low, indicating good characteristics.

In the above embodiment, 91PZN-9PT was used as the perovskite-type lead composite oxide single crystal, but Pb [(Mg _1/3 Nb _2/3 ) _1-y Ti _y ] O ₃ (where y Represents 0.20 ≦ y ≦ 0.40), Pb
_{[(Ni 1/3 Nb 2/3) 1} -z Ti z] O 3 ( provided that, z
Represents 0.30 ≦ z ≦ 0.50), Pb [(Co _1/3
Nb _2/3 ) _1-u Ti _u ] O ₃ (where u is 0.10 ≦
u ≦ 0.30), Pb [(A _1/2 Nb _1/2 ) _1-w
Ti _w ] O ₃ (where A is one selected from Sc, In, Fe, Y and a rare earth element, w is 0.30 ≦ w ≦
(Showing 0.50), it was confirmed that a piezoelectric element and an ultrasonic probe having the same excellent characteristics can be realized even when a single crystal of 0.50) was used. In the above embodiment, the single crystal is manufactured by the flux method, but may be manufactured by the Bridgman method, the kiloproth method, the hydrothermal growth method, or the like.

[0037]

As described above, the piezoelectric element according to the present invention has a high electromechanical coupling coefficient in which depolarization is suppressed and polarization insufficiency is improved. Further, even if the piezoelectric element has a large area having a width and a length of 20 mm or more, the variation in piezoelectric characteristics can be suppressed to 1% or less. As a result, high sensitivity,
It is possible to realize a large-sized ultrasonic probe having a wide band, and it is possible to achieve a remarkable effect such that the ultrasonic probe can be effectively used for an ultrasonic diagnostic apparatus and an ultrasonic flaw detector.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an array type ultrasonic probe provided with a piezoelectric element according to the present invention.

FIG. 2 is a perspective view showing a plurality of piezoelectric elements incorporated in the array type ultrasonic probe of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric body, 2 ... Backing material, 3, 4 ... Electrode, 5 ... Acoustic matching layer, 6 ... Acoustic lens, 7 ... Flexible printed wiring board, 8 ... Ground electrode.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 41/22 H01L 41/22 Z

Claims (3)

[Claims] 1. A piezoelectric element in which an electrode is formed on a piezoelectric body having a cut surface cut from a perovskite-type lead composite oxide single crystal, wherein the electrode forming surface of the piezoelectric body is a {100} plane, and A piezoelectric element, wherein a cut surface of the piezoelectric body is a {100} plane or a {110} plane. Wherein said perovskite lead composite oxide single _{crystal, Pb [(Zn 1/3 Nb 2/3} ) 1-x Ti x] O 3 ( here, x is 0.05 ≦ x ≦ 0.20 Pb [(Mg _1/3 Nb _2/3 ) _1-y Ti _y ] O ₃ (where y represents 0.20 ≦ y ≦ 0.40), Pb [(Ni _1/3 Nb _{2/3) 1-z Ti z]} O 3 ( provided that, z represents a 0.30 ≦ z ≦ 0.50), Pb [(Co 1/3 Nb 2/3) 1-u Ti u] O 3 (However, u indicates 0.10 ≦ u ≦ 0.30), Pb [(A _1/2 Nb _1/2 ) _1-w Ti _w ] O ₃ (However,
A is one kind selected from Sc, In, Fe, Y and a rare earth element, w represents 0.30 ≦ w ≦ 0.50) or a part of Pb in the above formula. The composition according to claim 1, wherein the composition is a composition in which at least one of Na, Sr, Ca, and La has been substituted in an amount of 10 mol% or less, or a composition in which a part of Nb in the above formula has been substituted with Ta.
The piezoelectric element as described in the above. 3. The piezoelectric element according to claim 1, wherein the perovskite-type lead composite oxide single crystal exhibits a rhombohedral crystal at a temperature of 100 ° C. or less.