JP2001328867A - Piezoelectric material and ultrasonic probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric material having a high Curie point, a large electromechanical coupling coefficient (k33'), excellent uniformity in composition and high reliability when used as a vibrator of an ultrasonic probe. SOLUTION: This piezoelectric material comprises a composition represented by the formula xPb(Mg1/3Nb2/3)O3-yPbTiO3-zPb(Zn1/3Nb2/3O3-wPb(Me1/2Nb1/2)O3 (Me is at least one kind of metal selected from In and Yb; and x+y+z+w=1) in which x, y, z and w are each specified as values falling into a region formed by linearly connecting points of a (x=0.80, y=0.20, z=0.00, w=0.00), b (x=0.02, y=0.98, z=0.00, w=0.00), c (x=0.02, y=0.02, z=0.96, w=0.00) and d (x=0.02, y=0.20, z=0.00, w=0.78).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric material and an ultrasonic probe useful for a medical diagnostic apparatus having a piezoelectric body made of the piezoelectric material.

[0002]

2. Description of the Related Art An ultrasonic probe has an ultrasonic transmitting / receiving element having a piezoelectric body. The ultrasonic probe is used to image an internal state of the object by irradiating ultrasonic waves toward the object and receiving reflected echoes from interfaces having different acoustic impedances in the object. An ultrasonic imaging apparatus incorporating such an ultrasonic probe is applied to, for example, a medical diagnostic apparatus for inspecting the inside of a human body and an inspection apparatus for detecting flaws inside metal welding.

In recent years, as one of the medical diagnostic apparatuses,
In addition to a tomographic image (B-mode image) of the human body, the color of the blood flow can be displayed in two dimensions using the Doppler shift caused by the ultrasonic blood flow in the heart, liver, carotid artery, and the like. A method adopting the "flow mapping (CFM) method" was developed, and the diagnostic capability of the medical diagnostic device was dramatically improved. The medical diagnostic device employing the CFM method can be used for any organ of the human body such as the uterus, liver, spleen,
Research is being carried out for a device that can be used to diagnose organs and that can also diagnose coronary thrombi.

[0004] In the case of the former B-mode image, it is required that a high-resolution image be obtained with high sensitivity so that small lesions and voids due to physical changes can be clearly seen to a deep part. In the case of the Doppler mode in which the latter CFM image can be obtained, since a reflected echo from a minute blood cell having a diameter of about several μm is used, the obtained signal level is smaller than that in the case of the B mode. Higher sensitivity is required.

Conventionally, the following materials and structures have been used for the ultrasonic transmitting / receiving element constituting the ultrasonic probe from the viewpoint of performance.

Ultrasonic attenuation when a living body is irradiated with ultrasonic waves by an ultrasonic probe is 0.5 to 1 dB / excluding bones and the like.
Since it is about MHz · cm, it is preferable to lower the frequency of the ultrasonic wave emitted from the ultrasonic transmitting / receiving element in order to obtain a highly sensitive signal from the living body. However, if the frequency is excessively lowered, the wavelength of the ultrasonic wave becomes longer and the resolution may be reduced. Therefore, the ultrasonic wave having a frequency of 2 to 10 MHz is usually emitted.

The piezoelectric material constituting the ultrasonic transmission / reception element is formed of a material having a large electromechanical coupling coefficient (k33 '), a small loss due to a cable or a device stray capacitance, and a large dielectric constant that is easy to match with a transmission / reception circuit. It is necessary to. Therefore, conventionally, the piezoelectric body is mainly formed of lead zirconate titanate (PZT) -based ceramic. Recently, lead zinc niobate and lead titanate (PZN)
T) has attracted attention because the electromechanical coupling coefficient (k33 ') of a composite oxide single crystal of a relaxor material represented by T) and lead titanate is superior to that of PZT. An ultrasonic probe having a transmitting / receiving element has also been proposed.

[0008] In these ultrasonic probes, there is a tendency to increase the driving voltage to be used as the resolution increases. Further, attempts have been made to convert the driving waveform, which was a unipolar pulse, to bipolar in order to increase the voltage amplitude. As a result, a large heat load is applied to the piezoelectric body constituting the ultrasonic transmitting / receiving element. PZT, PZNT
Since the structure of a perovskite-structure-type piezoelectric body represented by the formula (1) changes due to heat, the piezoelectricity may decrease or disappear before and after that. Therefore, a material having a high Curie point and a large electromechanical coupling coefficient (k33 ') is required for the piezoelectric material used in such an ultrasonic probe.

[0009] In response to such demands, PZT has a high Curie point but a small electromechanical coupling coefficient (k33 '), and PZNT mainly has a large electromechanical coupling coefficient (k33'). None of them satisfied the required characteristics, such as the Curie point was not so high. In recent years, in order to improve these characteristics, a system in which scandium is further dissolved in a composite oxide single crystal of a relaxor material and lead titanate has been attempted. In this piezoelectric material, the Curie point is increased and improved, but there is a disadvantage that the composition distribution of scandium in the initial stage and the final stage of single crystal growth has a large variation.
Variations in the composition cause variations in the characteristics within the crystal, and when obtaining a transducer for an ultrasonic probe from the single crystal, the crystal region that can be actually used is limited, and as a result, it is difficult to obtain a practical one.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric material having a large dielectric constant and a high Curie point, a large electromechanical coupling coefficient (k33 '), and excellent composition uniformity. Things.

Another object of the present invention is to provide an ultrasonic probe using the above-mentioned piezoelectric material, which can achieve high sensitivity and has high reliability.

[0012]

The piezoelectric material according to the present invention has the formula xPb (Mg1 / 3Nb2 / 3) 03-yPbTi.
O3-zPb (Zn1 / 3 Nb2 / 3) O3-wPb (Me1
/ 2 Nb1 / 2) O3 (where Me is at least one metal selected from In and Yb, x + y + z + w = 1.0
0, and x, y, z, and w are compositions defined as values of regions (except on the line segment ab) linearly connecting the following points a, b, c, and d, respectively. Containing Pb
(Mg1 / 3 Nb2 / 3) 03, PbTiO3, Pb (Zn1 /
3Nb2 / 3) O3 and Pb (Me1 / 2Nb1 / 2) O3 are drawn as vertices P1, P2, P3 and P4, respectively, and the coordinates of the vertices P1, P2, P3 and P4 are expressed as (X1, Y1, Z1, W1 = 1, 0, 0, 0),
(X2, Y2, Z2, W2 = 0, 1, 0, 0), (X3, Y
3, Z3, W3 = 0, 0, 1, 0), (X4, Y4, Z4, W
4 = 0, 0, 0, 1), a, b, c,
The point d is located on the plane of the equilateral triangular pyramid, and the coordinates X, Y, Z
And W.

XYZWa 0.80 0.20 0.00 0.00 b 0.02 0.98 0.00 0.00 c 0.02 0.02 0.96 0.00 d 0.02 0.20 0.00 0.78 The ultrasonic probe according to the present invention is formed on a piezoelectric body having an ultrasonic transmitting / receiving surface, and on an ultrasonic transmitting / receiving surface of the piezoelectric body and a surface opposite to the transmitting / receiving surface. And a pair of electrodes, wherein the piezoelectric body has the formula xPb (Mg1 / 3Nb
2/3) 03-yPbTiO3-zPb (Zn1 / 3Nb2 /
3) O3 -wPb (Me1 / 2 Nb1 / 2) O3 (However,
Me is at least one metal selected from In and Yb;
x + y + z + w = 1.00), x, y,
Each of z and w contains a composition defined as a value of a region (except on the line segment ab) linearly connecting the following points a, b, c, and d, and Pb (Mg1 / 3 Nb2 / 3) ) 03, P
bTiO3, Pb (Zn1 / 3Nb2 / 3) O3 and Pb (M
e1 / 2 Nb1 / 2) Draw a triangular pyramid having vertices P1, P2, P3 and P4, respectively,
2. Coordinates of P3 and P4 are (X1, Y1, Z1, W1
= 1, 0, 0, 0), (X2, Y2, Z2, W2 = 0, 1,
0,0), (X3, Y3, Z3, W3 = 0,0,1,0),
When expressed by (X4, Y4, Z4, W4 = 0, 0, 0, 1), the points a, b, c, and d are located on the plane of the regular triangular pyramid, and the coordinates X, Y, Z, and It is made of a piezoelectric material characterized by being represented by W.

XYZW a 0.80 0.20 0.00 0.00 b 0.02 0.98 0.00 0.00 c 0.02 0.02 0.96 0.00 d 0.02 0.20 0.00 0.78 Hereinafter, the piezoelectric material according to the present invention will be described in detail with reference to FIG.

The piezoelectric material of the present invention has the formula xPb (Mg1 /
3Nb2 / 3) 03-yPbTiO3-zPb (Zn1 / 3
Nb2 / 3) O3 -wPb (Me1 / 2 Nb1 / 2) O3 (where Me is at least one metal selected from In and Yb and represents x + y + z + w = 1.00)
Each of x, y, z and w contains a composition defined as a value (except on the line segment ab) of a region connecting the following points a, b, c and d linearly.

That is, as shown in FIG. 1, the equilateral triangular pyramid 1 is composed of Pb (Mg1 / 3Nb2 / 3) 03, PbTiO3, Pb (Z
n1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 / 2) O
3 are drawn as vertices P1, P2, P3 and P4, respectively, and the vertices P1, P2, P3 and P
The coordinates of 4 are (X1, Y1, Z1, W1 = 1, 0, 0,
0), (X2, Y2, Z2, W2 = 0, 1, 0, 0), (X
3, Y3, Z3, W3 = 0, 0, 1, 0), (X4, Y4, Z
4, W4 = 0, 0, 0, 1). For example, the midpoint of the height of the equilateral triangular pyramid 1 vertically lowered from the vertex P1 to the equilateral triangle connecting the P2, P3 and P4 is represented by coordinates (X = 0.5, Y = 0.5 / 3). , Z = 0.5 / 3, W
= 0.5 / 3). Further, in the equilateral triangular pyramid 1, the surface of the equilateral triangle parallel to the surface of the equilateral triangle and crossing the midpoint of the height has coordinates (X = 0.5, Y + Z + W =
0.5).

The points a, b, c and d defining the area are located on the plane of the triangular pyramid 1 and the coordinates X, Y of the vertices P1, P2, P3 and P4 of the triangular pyramid 1. , Z and W are represented as follows.

XYZW a 0.80 0.20 0.00 0.00 b 0.02 0.98 0.00 0.00 c 0.02 0.02 0.96 0.00 d 0.02 0.20 0.00 0.78 In other words, x, y, z, w are a (x = 0.80, y = 0.20, z = 0.00, w = 0.00) on the surface of the regular triangular pyramid 1 shown in FIG. ),
b (x = 0.02, y = 0.98, z = 0.00, w = 0.00), c (x = 0.0
2, y = 0.02, z = 0.96, w = 0.00), d (x = 0.02, y = 0.20,
z = 0.00, w = 0.78) is defined as a value (except on the line segment ab) of the area drawn by the triangular pyramid 2 connecting the points linearly.

The reason for defining the values of x, y, z and w of the composition contained in the piezoelectric material according to the present invention will be described below.

When x, y, z, and w are values outside the line segments ac, cd, and da in the area drawn by the triangular pyramid 2 in FIG. 1, the block made of the piezoelectric material containing the composition has a width of 150 μm or less. When processed into a rectangular piezoelectric body, the electromechanical coupling coefficient (k33 ') in the thickness direction is reduced to 60% or less. This is considered to be because the composition has no compositional phase boundary (MPB) in this range.

When x, y, z and w are near point b in the area drawn by the triangular pyramid 2 in FIG. 1, the electromechanical coupling coefficient (in the thickness direction) when processed into a rectangular piezoelectric body is obtained. k33 ') is not so large, but the electromechanical coupling coefficient (kt) in the thickness direction of the flat plate is large. Further, since the Curie point is high in this region, it is effective for application to a nondestructive inspection device at a high temperature.

Therefore, x, y, z and w are defined as values (except on the line segment ab) in the area drawn by the triangular pyramid 2 connecting the points a, b, c and d linearly in FIG. The piezoelectric single crystal material containing the composition described above has a high Curie point and a large electromechanical coupling coefficient (k33 'or kt). Further, the piezoelectric material has excellent composition uniformity, and as a result, provides uniform characteristics over a wide area. For this reason, when the piezoelectric material is used as a vibrator for an ultrasonic probe, almost the entire region of a crystal grown as a raw material can be used, which is efficient and economical.

The composition contained in the piezoelectric material according to the present invention is such that x, y, z and w have values (except on the line segment ab) in the region drawn by the triangular pyramid 2 in FIG.
(Mg1 / 3 Nb2 / 3) 03, PbTiO3, Pb (Zn1 /
It is preferable to include all of 3Nb2 / 3) O3 and Pb (Me1 / 2Nb1 / 2) O3.

Incidentally, Pb (Mg1 / 3 Nb2 / 3) 03-P
bTiO3-Pb (Zn1 / 3 Nb2 / 3) O3-Pb (Me1 /
In the composition represented by 2Nb1 / 2) O3 (where Me is at least one metal selected from In and Yb), the composition may slightly deviate from the stoichiometric ratio. Said Me
May be not only one kind but also a combination of two or more kinds.

Further, the composition comprises x, y, z and w
Have values in the area drawn by the triangular pyramid 2 in FIG. 1, and Pb (Mg1 / 3Nb2 / 3) 03, PbTiO3, Pb
(Zn1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 / 2)
) More preferably, it contains at least three components selected from O3 and the composition has a Curie point of 180 ° C or higher.

Further, the composition has 0.001 to 3 mol% of La203, Ta2O5 and WO3 whose x, y, w, and w have values in the area drawn by the triangular pyramid 2 in FIG. The characteristics can be improved by further containing at least one oxide selected from the group consisting of: By containing a predetermined amount of such an oxide,
The effect of increasing the electromechanical coupling coefficient (k33 ') in the thickness direction when the block is formed from the piezoelectric material into a rectangular shape is obtained.

The content of the oxide is specified for the following reasons. When the content of the oxide is 0.
When the content is less than 001 mol%, the effect of improving the electromechanical coupling coefficient is hardly effectively exhibited. On the other hand, when the content of the oxide exceeds 3 mol%, the oxides are segregated in a single crystal, and conversely, the oxide content increases. This causes a reduction in the mechanical coupling coefficient. A more preferred content of the oxide is in the range of 0.1 to 2 mol%.

Also in the composition to which the oxide is added, x, y, z and w have values in the region drawn by the triangular pyramid 2 in FIG. 1 and Pb (Mg1 / 3 Nb2 / 3)
O3, PbTiO3, Pb (Zn1 / 3Nb2 / 3) O3 and Pb (Me1 / 2Nb1 / 2) O3, and the composition has a Curie point of 180.
It is preferable that the temperature be equal to or higher than C.

The piezoelectric material according to the present invention is allowed to contain additives, substitutes, impurities, etc. other than the above oxides within a range not to impair the effects of the present invention. Specifically, Nd
Lanthanide elements such as 2O3, Sm2O3, MoO3, V2O5
And the like. Use of such an additive has the effect of increasing the electromechanical coupling coefficient (k33 ') in the thickness direction when a rectangular block is formed from the piezoelectric material block. In addition, Bi2O3, K2O, Sb2O3,
Impurities such as Cr2O3 and HfO2 may be contained in an amount of 0.1 mol% or less.

The more preferable composition of the composition constituting the piezoelectric material according to the present invention is represented by the formula xPb (Mg1 / 3
Nb2 / 3) 03-yPbTiO3-zPb (Zn1 / 3N
b2 / 3) O3 -wPb (Me1 / 2 Nb1 / 2) O3 x,
y, z, and w have values (except on the line segment ef) of a region connecting the following points e, f, g, h, i, and j linearly. That is, as shown in FIG. 2, Pb (Mg1 / 3
Nb2 / 3) 03, PbTiO3, Pb (Zn1 / 3 Nb2 / 3)
) O3 and Pb (Me1 / 2 Nb1 / 2) O3 are drawn as vertices P1, P2, P3 and P4, respectively, and the coordinates of the vertices P1, P2, P3 and P4 are represented by (X1, Y1, Z1), respectively. , W1 = 1, 0, 0, 0), (X2, Y
2, Z2, W2 = 0, 1, 0, 0), (X3, Y3, Z3, W3
= 0,0,1,0), (X4, Y4, Z4, W4 = 0,0,
0, 1), the points of e, f, g, h, i, and j are located on the plane of the regular triangular pyramid 1, and the coordinates X, Y,
Represented by Z and W.

XYZ We 0.75 0.25 0.00 0.00 f 0.40 0.60 0.00 0.00 g 0.02 0.02 0.96 0.00 h 0.02 0.20 0.78 0.00 i 0.02 0.28 0.00 0.70 j 0.02 0.55 0.00 0.43 In other words, x, y, z and w are shown in FIG. E (X = 0.75, Y = 0.25, Z = 0.00, W = 0.00) on the surface of the regular triangular pyramid 1 shown,
f (X = 0.40, Y = 0.60, Z = 0.00, W = 0.00), g (X = 0.0
2, Y = 0.02, Z = 0.96, W = 0.00), h (X = 0.02, Y = 0.20,
Z = 0.78, W = 0.00), i (X = 0.02, Y = 0.28, Z = 0.00, W
= 0.70) and j (X = 0.02, Y = 0.55, Z = 0.00, W = 0.43)
) Are defined as values (excluding on the line segment ef) of an area drawn by the triangular prism 3 connecting the points in a straight line.

The values x (y, z, w) of the region (line segment ef) drawn by a triangular prism 3 connecting points e, f, g, h, i, and j shown in FIG. The piezoelectric material containing the composition (excluding the above) has a larger electromechanical coupling coefficient (k33 ').

Next, a method for manufacturing the piezoelectric material of the present invention will be described. FIG. 4 shows an example of an apparatus for growing a single crystal material to be the piezoelectric material of the present invention. In FIG. 4, an electric furnace 19 includes a coil-shaped heater 20 therein, and a platinum crucible 21 is provided inside the electric furnace surrounded by the heater 20. A single crystal material 22 having a predetermined composition is put in a platinum crucible 21 and heated to obtain a single crystal 23.

As a manufacturing method, for example, first, Pb, M
g, an oxide of ZnIn, Yb, Nb, Ti, or the like, or a carbonate, oxalate, hydroxide, organic compound, or the like, which becomes an oxide upon firing, is weighed to a required number of moles, sufficiently mixed, and pulverized to 700.
Calcinate at ~ 900 ° C.

The calcined powder is mixed with lead oxide (PbO) or boron oxide (B 2 O 3) as a flux at a desired ratio and then filled in a platinum crucible. Subsequently, the temperature of the mixture in the platinum crucible is raised to 1000 to 1400 ° C., and after holding for several hours, the mixture is cooled to 850 ° C. at 0.2 to 10 ° C./hour. Thereafter, the molten mixture in the crucible is cooled to room temperature and boiled with an aqueous nitric acid solution to take out a single crystal (piezoelectric material).

The piezoelectric material obtained by such a method is processed into a desired shape with the orientation determined using a Laue X-ray apparatus, and electrodes are formed on the obtained piezoelectric material.
By applying an electric field of 1 to 30 KV / mm at a temperature of 0 ° C., polarization is performed to produce a vibrator. As a method for producing the single crystal, other than the flux method, a kiloplus method, a Czochralski method, a Bridgman method, a hydrothermal growth method, a thin film method, or the like can be employed.

Next, an ultrasonic probe according to the present invention will be described in detail with reference to FIG. A plurality of piezoelectric bodies 11 made of a piezoelectric material are separately bonded to each other on a backing material 12. Each of the piezoelectric bodies 11 vibrates in the direction of arrow A in the figure. The first electrode 13 is formed from the ultrasonic transmitting / receiving surface of each of the piezoelectric bodies 11 to a side surface thereof and a part of a surface opposite to the transmitting / receiving surface. The second electrode 14 is formed on a surface of each of the piezoelectric bodies 11 opposite to the transmission / reception surface at a desired distance from the first electrode 13. The piezoelectric body 11 and the first and second electrodes 13 and 14 constitute an ultrasonic transmitting / receiving element. The acoustic matching layer 15 is formed on the ultrasonic transmitting and receiving surface of each of the piezoelectric bodies 11 including each of the first electrodes 13. The acoustic lens 16 is formed over the entire acoustic matching layer 15. The flexible printed wiring board 17 is connected to each of the first electrodes 13. The ground electrode plate 18 is connected to each of the second electrodes 14 by, for example, soldering. A plurality of conductors (cables) not shown are connected to the flexible printed wiring board 17 and the ground electrode plate 18, respectively.

The ultrasonic probe having the structure shown in FIG. 3 is manufactured by, for example, the following method. First,
For example, a conductive film is deposited by sputtering on a piezoelectric material made of a flat sintered body, 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 piezoelectric material which will be the ultrasonic transmitting / receiving surface, and these are adhered to the backing material 12. Subsequently, the first and second electrodes 1 are formed on the backing material 12 by cutting a plurality of times from the acoustic matching layer to the piezoelectric material using a blade.
A plurality of piezoelectric bodies 11 separated from each other having 3 and 14 and a plurality of acoustic matching layers 15 arranged on each of the piezoelectric bodies 11 are formed. Next, after forming an acoustic lens 16 on the acoustic matching layer 15, a flexible printed wiring board 17 is connected to each of the first electrodes 13, and an earth electrode plate 18 is connected to the second electrode 14 by, for example, soldering. Further, an ultrasonic probe is manufactured by connecting a plurality of conductors (cables) (not shown) to the flexible printed wiring board 17 and the ground electrode plate 18, respectively.

The width of the piezoelectric body 11 is 150 μm.
The following is preferred. The first and second electrodes 13,
14 is, for example, Ti / Au, Ni / Au or Cr / A
u is formed from a two-layer metal film.

The piezoelectric body 11 has the formula xPb (Mg1 / 3
Nb2 / 3) 03-yPbTiO3-zPb (Zn1 / 3N
b2 / 3) O3 -wPb (Me1 / 2 Nb1 / 2) O3 (where Me is at least one metal selected from In and Yb, and represents x + y + z + w = 1.00);
Each of y, z and w is made of a piezoelectric material containing a composition defined as a value (except on the line segment ab) of a region connecting the following points a, b, c and d linearly. That is, as shown in FIG. 1 described above, Pb (Mg1 / 3Nb2 / 3) 03,
PbTiO3, Pb (Zn1 / 3 Nb2 / 3) O3 and Pb
(Me1 / 2 Nb1 / 2) O3 is assigned to vertices P1, P2, P3, respectively.
And draw a regular triangular pyramid having as P4, the vertex P1,
Let the coordinates of P2, P3 and P4 be (X1, Y1, Z1,
W1 = 1, 0, 0, 0), (X2, Y2, Z2, W2 = 0,
1,0,0), (X3, Y3, Z3, W3 = 0,0,1,
0), (X4, Y4, Z4, W4 = 0, 0, 0, 1), the points a, b, c, d are located on the plane of the regular triangular pyramid, and the coordinates X, Y , Z, and W.

XYZWa 0.80 0.20 0.00 0.00 b 0.02 0.98 0.00 0.00 c 0.02 0.02 0.96 0.00 d 0.02 0.20 0.00 0.78 The composition contained in the piezoelectric material according to the present invention is x, y,
While z and w have values in the area drawn by the triangular pyramid 2 in FIG. 1, Pb (Mg1 / 3Nb2 / 3) 03, PbTi
O3, Pb (Zn1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2
It is preferable to include all Nb1 / 2) O3.

The piezoelectric body 11 is represented by the above formula, and x,
y, z and w are e (X = 0.75, Y = 0.25, Z = 0.00, W = 0.00) on the surface of the regular triangular pyramid 1 shown in FIG.
f (X = 0.40, Y = 0.60, Z = 0.00, W = 0.00), g (X = 0.0
2, Y = 0.02, Z = 0.96, W = 0.00), h (X = 0.02, Y = 0.20,
Z = 0.78, W = 0.00), i (X = 0.02, Y = 0.28, Z = 0.00, W
= 0.70) and j (X = 0.02, Y = 0.55, Z = 0.00, W = 0.43)
) Are more preferably formed of a piezoelectric material containing a composition defined as a value (excluding on the line segment ef) of a region drawn by a triangular prism 3 connecting the points linearly.

The piezoelectric body 11 is added to the composition by 0.00
It is allowed to be formed from a piezoelectric material further containing 1 to 3 mol% of at least one oxide selected from the group consisting of La203, Ta2O5 and WO3. The content of the oxide is specified for the same reason as described for the piezoelectric material.

An ultrasonic probe according to the present invention includes a piezoelectric body made of a piezoelectric material containing the composition described above.
The piezoelectric material having such a composition has a high Curie point and a large electromechanical coupling coefficient (k33 '). Therefore, an ultrasonic probe including a piezoelectric body made of such a piezoelectric material has high sensitivity. It can have high resolution and high reliability.

Further, since the piezoelectric body has a high Curie point, it can be applied to the piezoelectric body without causing high voltage (generation of heat) or depolarization due to bipolar pulse driving. As a result, it is possible to realize an ultrasonic probe that emits an ultrasonic wave having an extremely strong impact force due to the interaction of the piezoelectric body with a large electromechanical coupling coefficient (k33 ').
Such an ultrasonic probe can be effectively used for a calculus crushing device and the like.

[0046]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail. Examples 1 to 20 In a 0.7 liter polyethylene pot, zirconia balls and pure water were used to weigh, pulverize and mix Mg0 and Nb2O5 having a purity of 99.9% or more at a molar ratio of 1: 2. After that, it was dried and calcined at 1200 ° C. for 4 hours. The obtained calcined product was pulverized again in the pot to prepare a submicron MgNb2O6 powder.

Similarly, Zn0 having a purity of 99.9% or more is used.
And Nb2O5 were weighed at a molar ratio of 1: 2, pulverized, mixed, dried, and calcined at 1100 ° C. for 4 hours. The calcined product was pulverized again in the pot to prepare a submicron ZnNb2O6 powder.

Next, In2O3 having a purity of 99.9% or more is used.
And Yb2O3 and Nb2O5 were weighed so as to be equimolar, crushed and mixed, dried, and further dried.
Calcination was performed at 100 ° C. for 4 hours. The obtained calcined product was pulverized again in the pot to obtain sub-micron InNbO4, YbN.
Each of bO4 powder was prepared.

Subsequently, these powders and a purity of 99.9%
The above PbO, TiO and the additives shown in Tables 1 and 3 were weighed so as to have the compositions shown in Tables 1 and 3, respectively, and were crushed and mixed in a pot mill using zirconia balls and pure water. Thereafter, it was dried and calcined at 800 ° C. for 2 hours.
Each of the obtained calcined materials was pulverized again in a pot to produce a submicron powder.

[0050]

[Table 1]

[0051]

[Table 3]

Next, each of the calcined powder and lead oxide was mixed in a ratio of 1:
3 and mix 1 kg of these mixtures in 200 ml
And placed in a platinum crucible and sealed with a platinum lid.
Subsequently, each of the crucibles was set in an electric furnace, and the temperature was raised to 1250 ° C. at a rate of 100 ° C./hour. After holding for 6 hours, oxygen was introduced into the lower part of each of the crucibles, and the oxygen flow rate was adjusted so that the bottom was lower by 20 ° C. or more than the upper surface. Subsequently, it was cooled to 850 ° C. at 1 ° C./hour. Thereafter, the mixture is cooled to room temperature, and 24% with a 20% aqueous nitric acid solution.
The mixture was boiled for an hour, and a single crystal as a piezoelectric material was taken out. Each of the obtained single crystals was a square plate having a 10 mm square.

The orientation of each single crystal is set to [100],
These were processed to produce square plate samples of 8 mm × 8 mm × 0.4 mm. A Ti / Au conductor film is deposited on the upper and lower surfaces and side surfaces of these square plates by a sputtering method, and is opposite to the conductive film portion located on one side surface of the square plate and a surface to be an ultrasonic transmitting / receiving surface by a selective etching technique. A part of the conductive film located on the side surface was removed. Silico
This was cooled to 25 ° C. while applying an electric field of 200 ° C. × 15 kV / mm in an oil, and polarization was performed. The dielectric constant of these samples was measured. Further, the electromechanical coupling coefficient (kt) in the thickness direction of the flat plate was measured by a resonance-anti-resonance method. Next, each of the single crystals was cut out from a rectangular sample having a width of 150 μm, a thickness of 400 μm, and a length of 6 mm using a dicing saw, and the electromechanical coupling coefficient (k33 ′) in the thickness direction was similarly determined for these samples. Was measured. The electromechanical coupling coefficients (k33 'and kt)
Was determined by the equation 1 using the resonance-anti-resonance method.

[0054]

(Equation 1)

Where fr in the equation is the resonance frequency, fa
Indicates an anti-resonance frequency, respectively.

Tables 2 and 4 show the obtained results.

[0057]

[Table 2]

[0058]

[Table 4]

Next, the temperature dependence of the electromechanical coupling coefficient (k33 ') of each single crystal was investigated in the range from room temperature to 200 ° C. Electromechanical coupling coefficient at room temperature (k33 ') and 100
Tables 2 and 4 show the rates of change of the electromechanical coupling coefficient (k33 ') at ° C.

Further, the above-mentioned array type ultrasonic probe shown in FIG. 3 was manufactured using each of the disk-shaped sintered bodies.
That is, the disk-shaped sintered body is processed to have a width of 10 mm,
A square plate having a length of 10 mm and a thickness of 400 μm was prepared. 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, and the conductive film portion located on one side surface of the square plate and a surface serving as an ultrasonic transmitting / receiving surface are positioned by a selective etching technique. A part of the conductive film located on the opposite surface was removed. Subsequently, after an acoustic matching layer 15 was formed on the surface of the square plate to be an ultrasonic transmitting / receiving surface, these were adhered onto the backing material 12. Subsequently, the rectangular plate was cut from the acoustic matching layer 15 using a diamond blade, and cut into strips having a width of 150 μm. By this cutting, the separated width 1 having the first and second electrodes 13 and 14 on the backing material 12 is obtained.
There were formed 100 piezoelectric bodies 11 having a thickness of 50 μm, a length of 10 mm, a thickness of 400 μm, and a plurality of acoustic matching layers 15 arranged on each of the piezoelectric bodies 11. Next, after an acoustic lens 16 was formed on the acoustic matching layer 15, a flexible printed wiring board 17 was connected to the conductive film portion provided for the first electrode 13 by soldering. Also,
The ground electrode 18 was connected to the conductive film portion provided for the second electrode 14 by soldering. The flexible printed wiring board 17 and the ground electrode 18 may be connected to the conductor film using a conductive paste. 11 not shown
An array type ultrasonic probe was manufactured by connecting a plurality of conductors (cables) each having a length of 0 pF / m and a length of 2 m to the flexible printed wiring board 17 and the ground electrode plate 18, respectively.

No depolarization occurred and no reduction in sensitivity was observed in either the case where the obtained array type ultrasonic probe was driven at a high voltage or the case where a bipolar pulse drive was performed. Examples 21 to 22 First, using a zirconia ball and pure water in a 0.7 liter polyethylene pot, the purity of M was 99.9% or more.
g0 and Nb2O5 were weighed at a molar ratio of 1: 2, pulverized, mixed, dried, and calcined at 1200 DEG C. for 4 hours.
The obtained calcined product was pulverized again in the pot to prepare a submicron MgNb2O6 powder.

Similarly, Zn0 having a purity of 99.9% or more is used.
And Nb2O5 were weighed at a molar ratio of 1: 2, pulverized, mixed, dried, and calcined at 1100 DEG C. for 4 hours. The calcined product was pulverized again in the pot to prepare a submicron ZnNb2O6 powder.

Next, In2O3 having a purity of 99.9% or more is used.
And Nb2O5 were weighed so as to be equimolar, pulverized, mixed, dried, and further calcined at 1100 DEG C. for 4 hours.
The calcined product was pulverized again in the pot to prepare sub-micron InNbO4 powder.

Subsequently, these powders and the purity were 99.9%
The above PbO, TiO and the composition shown in Table 5 were weighed, crushed and mixed using a zirconia ball and pure water in a pot mill, dried, and calcined at 800 ° C. for 2 hours. Each of the obtained calcined materials was pulverized again in a pot to produce a submicron powder.

[0065]

[Table 5]

Each of the calcined powders and lead oxide were mixed at a ratio of 1: 3, and these mixtures were respectively placed in platinum crucibles of 15 mmφ × 200 mm, and sealed with a platinum lid. Subsequently, the temperature at the center shown in FIG.
The platinum crucible 20 is placed in a vertical electric furnace 19 having an inner diameter of 50 mm and a length of 1000 mm at 50 ° C. and an average temperature gradient in the vertical direction of 0.5 ° C./mm to 3 ° C./mm by the heater 2 divided into two vertically. After raising the temperature to 1250 ° C. in 7 hours and holding for 6 hours,
The crystal raw material in was melted. Next, the platinum crucible 2
0 was lowered at a slow speed by about 500 mm toward the lower temperature gradient portion by the center of the electric furnace 19, and then allowed to cool to room temperature. The platinum crucible was broken, and the contents were taken out. The mixture was boiled with a 20% aqueous nitric acid solution for 24 hours to take out a single crystal as a piezoelectric material. Each single crystal obtained is 15
It was about mmφ × 20 mm. From each nucleus generation point, each single crystal was cut out at a flat plate sample of about 0.5 mm at an interval of 4 mm, each of which was cut into five pieces. These are processed to 5mm x 5mm x
Each 0.4 mm square plate sample was produced. A Ti / Au conductor film is deposited on the upper and lower surfaces and side surfaces of these square plates by a sputtering method, and is opposite to the conductive film portion located on one side surface of the square plate and a surface to be an ultrasonic transmitting / receiving surface by a selective etching technique. A part of the conductive film located on the side surface was removed. Thereafter, the temperature characteristics of the dielectric constant of these samples were measured. Table 6 shows the results.

[0067]

[Table 6]

It can be seen that the dispersion of the dielectric constant and the Curie point at room temperature is very small in all the compositions of the examples. When the single crystal is used as an ultrasonic probe vibrator, almost all regions of the grown crystal can be used because the characteristic variation is small, so that it is efficient and economical. Comparative Examples 1 and 2 Table 7 shows systems containing scandium as Comparative Examples 1 and 2. The comparative example is represented by the following chemical formula. xPb
(Mg1 / 3Nb2 / 3) 03-yPbTiO3-zPb
(Zn1 / 3 Nb2 / 3) O3 -wPb (Sc1 / 2 Nb1 / 2
) O3 (provided that x + y + z + w = 1.00).

[0069]

[Table 7]

First, a zirconia ball and pure water were used in a 0.7 liter polyethylene pot to give a purity of 99.
9% or more of Mg0 and Nb2O5 were weighed at a molar ratio of 1: 2, pulverized and mixed, dried, and calcined at 1200 DEG C. for 4 hours. The obtained calcined product was pulverized again in the pot to prepare a submicron MgNb2O6 powder.

Similarly, Zn0 having a purity of 99.9% or more is used.
And Nb2O5 were weighed at a molar ratio of 1: 2, pulverized, mixed, dried, and calcined at 1100 DEG C. for 4 hours. The calcined product was pulverized again in the pot to prepare a submicron ZnNb2O6 powder.

Next, Sc2O3 having a purity of 99.9% or more is used.
And Nb2O5 were weighed so as to be equimolar, pulverized, mixed, dried, and further calcined at 1100 DEG C. for 4 hours.
The calcined product was pulverized again in the pot to prepare sub-micron InNbO4 powder.

Subsequently, these powders and the purity were 99.9%
The above PbO, TiO and the composition shown in Table 7 were weighed, crushed and mixed in a pot mill using zirconia balls and pure water, dried, and calcined at 800 ° C. for 2 hours. Each of the obtained calcined materials was pulverized again in a pot to produce a submicron powder.

Each of the calcined powders and lead oxide were mixed at a ratio of 1: 3, and these mixtures were put into platinum crucibles of 15 mmφ × 200 mm, respectively, and sealed with a platinum lid. Subsequently, the temperature at the center shown in FIG.
The platinum crucible 20 is placed in a vertical electric furnace 19 having an inner diameter of 50 mm and a length of 1000 mm at 50 ° C. and an average temperature gradient in the vertical direction of 0.5 ° C./mm to 3 ° C./mm by the heater 2 divided into two vertically. After raising the temperature to 1450 ° C. in 7 hours and holding for 6 hours,
The crystal raw material in was melted. Next, the platinum crucible 2
0 was lowered at a slow speed by about 500 mm toward the lower temperature gradient portion by the center of the electric furnace 19, and then allowed to cool to room temperature. The platinum crucible was broken, and the contents were taken out. Thereafter, the mixture was boiled with a 20% nitric acid aqueous solution for 24 hours to take out a single crystal as a piezoelectric material. Each of the obtained single crystals was about 15 mmφ × 20 mm. From each nucleus generation point, each single crystal was cut out at a flat plate sample of about 0.5 mm at an interval of 4 mm, each of which was cut into five pieces. These are processed to 5mm x 5
Each square plate sample of mm × 0.4 mm was prepared. A Ti / Au conductor film is deposited on the upper and lower surfaces and side surfaces of these square plates by a sputtering method, and is opposite to the conductive film portion located on one side surface of the square plate and a surface to be an ultrasonic transmitting / receiving surface by a selective etching technique. A part of the conductive film located on the side surface was removed. Thereafter, the temperature characteristics of the dielectric constant of these samples were measured. Table 8 shows the results.

[0075]

[Table 8]

It can be seen that the dispersion of the dielectric constant and Curie point at room temperature in all the compositions of this comparative example is very large. When the single crystal is used as a transducer for an ultrasonic probe because of a large variation in characteristics, a portion with uniform characteristics obtained from a grown crystal becomes a narrow region, which is uneconomical.

[0077]

As described above, according to the present invention, a piezoelectric material having a large dielectric constant, a high Curie point, and a large electromechanical coupling coefficient (k33 ') in the thickness direction when processed into a rectangular shape. Can be provided. Further, the piezoelectric material of the present invention has excellent composition uniformity, and can utilize a wide area of the grown single crystal. Therefore, the ultrasonic probe including the piezoelectric body made of the piezoelectric material of the present invention in the ultrasonic transmitting / receiving element can realize the performance of high sensitivity and high resolution at a low cost for a long time without fear of depolarization due to heat generation during driving. .

[Brief description of the drawings]

FIG. 1 is a quaternary diagram showing a composition range included in a piezoelectric material according to the present invention.

FIG. 2 is a quaternary diagram showing a more preferable composition range included in the piezoelectric material according to the present invention.

FIG. 3 is a perspective view showing an ultrasonic probe according to the present invention.

FIG. 4 is a schematic diagram showing a growing apparatus for manufacturing a piezoelectric material (single crystal) according to the present invention.

[Explanation of symbols]

1 ... equilateral triangular pyramid, 2 ... triangular pyramid, 3 ... triangular prism, 11 ... piezoelectric body, 12
... Backing material, 13,14 ... Electrode, 15 ... Acoustic matching layer, 16 ... Acoustic lens, 17 ... Flexible printed wiring board, 1
8 Earth electrode 19 Electric furnace 20 Heater 21 Platinum crucible 22 Single crystal raw material 23 Single crystal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 41/187 H01L 41/08 U H04R 17/00 332 41/18 101F (72) Inventor Yohachi Yamashita Kanagawa 1F, Kobayashi-Toshiba-cho, Kawasaki-shi, Pref. F-term in the Toshiba R & D Center (reference) AA07 AA11 AA14 AA26 AA27 AA32 BA10 5D019 AA21 BB18 FF04

Claims (8)

[Claims] 1. The formula xPb (Mg1 / 3Nb2 / 3) 03-
yPbTiO3 -zPb (Zn1 / 3Nb2 / 3) O3-w
Pb (Me1 / 2 Nb1 / 2) O3 (where Me is In,
At least one metal selected from Yb, x + y + z +
w = 1.00), and x, y, z, and w are defined as values (except on the line segment ab) of the following linearly connecting points a, b, c, and d, respectively. Pb (Mg1 / 3Nb2 / 3) 03, PbTiO3, Pb
b (Zn1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 /
2) Draw a regular triangular pyramid having O3 as vertices P1, P2, P3 and P4, respectively, and coordinate the vertices P1, P2, P3 and P4 with (X1, Y1, Z1, W1 = 1, 0,
0,0), (X2, Y2, Z2, W2 = 0,1,0,0),
(X3, Y3, Z3, W3 = 0, 0, 1, 0), (X4, Y
When expressed as 4, Z4, W4 = 0, 0, 0, 1), the points a, b, c, and d are located on the plane of the regular triangular pyramid, and are represented by coordinates X, Y, Z, and W. A piezoelectric material. XYZW a 0.80 0.20 0.00 0.00 b 0.02 0.98 0.00 0.00 c 0.02 0.02 0.96 0.00 d 0.02 0.20 0.00 0.78 2. The composition according to claim 1, wherein x, y, z and w have values in the above range, and Pb (Mg1 / 3 Nb2 / 3).
2. The piezoelectric material according to claim 1, wherein said piezoelectric material contains all of O3, PbTiO3, Pb (Zn1 / 3Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 / 2) O3. 3. 0.001 to 3 mol% of La203, Ta
2. The piezoelectric material according to claim 1, wherein at least one oxide selected from the group consisting of 2O5 and WO3 is further added to the composition. 4. The composition to which the oxide is added,
x, y, z and w have values in the region,
Pb (Mg1 / 3 Nb2 / 3) 03, PbTiO3, Pb (Z
n1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 / 2) O
The piezoelectric material according to claim 3, comprising at least three kinds of components selected from (3) and a Curie point of the composition is 180 ° C or higher. 5. A piezoelectric body having an ultrasonic transmitting / receiving surface, and a pair of electrodes formed on an ultrasonic transmitting / receiving surface of the piezoelectric body and a surface opposite to the transmitting / receiving surface, respectively, wherein the piezoelectric body comprises: Formula xPb (Mg1 / 3Nb2 / 3) 03-yPb
TiO3 -zPb (Zn1 / 3 Nb2 / 3) O3 -wPb
(Me1 / 2 Nb1 / 2) O3 (Me is In, Yb
At least one metal selected from the group consisting of x + y + z + w =
1.00), and x, y, z, and w are defined as values (except on the line segment ab) of the following linearly connecting points a, b, c, and d, respectively. Pb (Mg1 / 3 Nb2 / 3) 03, PbTiO3, Pb
(Zn1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 / 2)
) Draw a regular triangular pyramid having O3 as vertices P1, P2, P3 and P4, respectively, and coordinate the vertices P1, P2, P3 and P4 with (X1, Y1, Z1, W1 = 1, 0,
0,0), (X2, Y2, Z2, W2 = 0,1,0,0),
(X3, Y3, Z3, W3 = 0, 0, 1, 0), (X4, Y
When expressed as 4, Z4, W4 = 0, 0, 0, 1), the points a, b, c, and d are located on the plane of the regular triangular pyramid, and are represented by coordinates X, Y, Z, and W. An ultrasonic probe comprising a piezoelectric material. XYZW a 0.80 0.20 0.00 0.00 b 0.02 0.98 0.00 0.00 c 0.02 0.02 0.96 0.00 d 0.02 0.20 0.00 0.78 6. The composition constituting the piezoelectric material,
x, y, z and w have values in the region,
Pb (Mg1 / 3 Nb2 / 3) 03, PbTiO3, Pb (Z
n1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 / 2) O
6. The ultrasonic probe according to claim 5, wherein all three are included. 7. The composition according to claim 7, wherein the piezoelectric material comprises
The ultrasonic probe according to claim 5, further comprising 1 to 3 mol% of at least one oxide selected from the group consisting of La203, Ta2O5 and WO3. 8. The composition to which the oxide is added,
x, y, z and w have values in the region,
Pb (Mg1 / 3 Nb2 / 3) 03, PbTiO3, Pb (Z
n1 / 3 Nb2 / 3) O3 and Pb (Me1 / 2 Nb1 / 2) O
The ultrasonic probe according to claim 7, comprising at least three kinds of components selected from (3), and the Curie point of the composition is 180 ° C or higher.