DESCRIPTION JP2004289493

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DESCRIPTION JP2004289493
The present invention provides an ultrasonic transducer which has a short time waveform, wide
frequency characteristics, generates ultrasonic pulses with large amplitude with good
reproducibility, and enables high resolution and high sensitivity measurement. A piezoelectric
plate comprising a single multi-component piezoelectric ceramic and having a piezoelectric h
constant inclined in a thickness direction, wherein the inclination of the piezoelectric h constant
is optimized. [Selected figure] Figure 7
Piezoelectric plate, method of manufacturing the same, and ultrasonic transducer using the same
The present invention relates to a ceramic piezoelectric plate used for an ultrasonic transducer
and the like, and an ultrasonic transducer using the piezoelectric plate. [0002] Ultrasonic
transducers using ceramic piezoelectric materials are widely used in various ultrasonic
measurement devices such as medical diagnostic devices, nondestructive inspection devices, fish
finders and the like. These devices mainly input electrical pulses to an ultrasonic transducer to
generate ultrasonic waves, propagate the ultrasonic waves into the medium, and reflect the
reflected waves from different parts of the acoustic impedance present in the medium. The
ultrasonic echo method which detects and measures is used. If the acoustic impedance between
the two media is the same, the sound wave is transmitted well and the reflected wave is very
small, but between the media with different acoustic impedance, the sound wave is reflected at
the boundary and the transmission is transmitted if the difference is large There are few waves
and many reflected waves. It is an ultrasonic echo method that utilized this. Since ultrasonic
measurement equipment is required to have high resolution and to be able to measure over a
wide frequency band, shortening the time waveform of ultrasonic pulses generated from the
ultrasonic transducer as much as possible, and It is desirable to generate an ultrasonic pulse
having a wide band frequency characteristic. In general, metal electrode films are formed on both
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sides of a piezoelectric ceramic plate (hereinafter referred to as a piezoelectric plate) polarized in
the thickness direction, and the main part of the ultrasonic transducer is formed on one side of
the piezoelectric plate. As a backing material, a ceramic plate of the same material is attached via
an electrode film, and a sound absorbing material is formed behind it. The ultrasonic pulse is
excited by applying an impulse voltage to the piezoelectric plate. When using a ceramic plate in
which piezoelectric h constants are uniformly distributed in the thickness direction as the
piezoelectric plate, ultrasonic waves radiated to the outside from the surface of the piezoelectric
plate when the ultrasonic transducer is driven by a voltage pulse The pulse time waveform forms
a long pulse train instead of a single pulse, and the time waveform becomes long. There is also a
problem that the frequency band is narrow. On the other hand, it is known that a short pulse
ultrasonic wave having a wide frequency bandwidth can be obtained by using a piezoelectric
plate whose piezoelectric h constant is linearly or monotonically inclined in the thickness
direction. (See, for example, Patent Document 1). The difference is that when using a
piezoelectric plate with uniformly distributed piezoelectric h constants, ultrasonic pulses are
generated from both sides of the piezoelectric plate, while using a tilted piezoelectric plate with
an inclined piezoelectric h constant The reason is that ultrasonic waves are emitted only from
one side of the piezoelectric constant.
The inventors of the present invention have also previously made an inclined piezoelectric plate
in which the piezoelectric h constant is inclined monotonously and smoothly by spatially
changing the component ratio of the component metal elements, and ultrasonic conversion using
this inclined piezoelectric plate Japanese Patent Application No. 2002-378540 has been
proposed. Patent Document 1: Japanese Patent Application Laid-Open No. 7-154897 SUMMARY
OF THE INVENTION In the ultrasonic measurement apparatus, in addition to the short time
waveform of the ultrasonic pulse to be emitted, In order to improve the transmission sensitivity
of the ultrasonic transducer, a large pulse amplitude is required. However, according to studies
by the present inventors, even if a short pulse having a wide frequency bandwidth is obtained by
spatially tilting the piezoelectric h constant, the amplitude of the ultrasonic pulse differs
depending on the manner of tilting, It has been found that if the piezoelectric h constant is
merely linearly or monotonically inclined, as shown in FIGS. 12 and 14, an ultrasonic pulse with
a large amplitude can not always be obtained. Therefore, it has been difficult to reproducibly
obtain an ultrasonic transducer with high sensitivity. The present invention relates to an
ultrasonic transducer used in an ultrasonic echo method, in which the degree of spatial
inclination of the piezoelectric h constant of the piezoelectric ceramic is controlled and optimized
to shorten and widen the time waveform. An object of the present invention is to obtain an
ultrasonic pulse having a large amplitude with good reproducibility while having frequency
characteristics and to provide an ultrasonic transducer capable of high resolution and high
sensitivity measurement. Another object of the present invention is to provide a highly practical
ultrasonic transducer in which the spatial gradient of the piezoelectric h constant of the
piezoelectric ceramic is optimized and there is no structural acoustic discontinuity. It is an object
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of the present invention to provide a method of easy manufacture. The gist of the present
invention is as follows. 1. A piezoelectric plate made of multi-component piezoelectric ceramic, in
which the piezoelectric h constant is zero on one side and maximum on the other side, and
inclined in the thickness direction so as to satisfy the following conditions A piezoelectric plate
characterized in that (2) <img class = "EMIRef" id = "198292035-00003" /> (2) h (x) <h (t) (3) 0
≦ x in the range of 0 ≦ x <t In the range of <t, h (x)> (x) in the range of at least 0.8t ≦ x <t, 0 ≦
dh (x) / dx ≦ 2 × 10 <13> (V / m <2>) (4) h (t) / t) x where x is the distance in the thickness
direction from the plane where the piezoelectric h constant is zero (m), t is the thickness of the
piezoelectric plate (m), h (x) is the distance x The piezoelectric h constant (V / m) and h (t) in are
the piezoelectric h constant (V / m) at a distance t.
In the range of 2.0 <x <t, h (x)> (h (t) / t) · x, and d <2> h (x) / dx <2> ≦ 0, as described in 1
above. Piezoelectric plate. ３． The piezoelectric plate according to 1 or 2, wherein the
piezoelectric h constant is inclined by inclining the component ratio of the component metal
element in the thickness direction. 【００１２】 ４． Prepare two or more types of porcelain
powders having different piezoelectric h constants, prepare green sheets using the respective
porcelain powders, laminate the green sheets, press-fit, and then sinter the piezoelectric h
constants by sintering. The method for manufacturing a piezoelectric plate according to any one
of 1 to 3 above. ５． The method for producing a piezoelectric plate according to the above 4,
wherein the two or more types of ceramic powder contain the same component and change the
ratio of the component metal element to change the piezoelectric h constant. ６． An ultrasonic
transducer using the piezoelectric plate according to any one of the above 1 to 3. BEST MODE
FOR CARRYING OUT THE INVENTION The piezoelectric plate of the present invention is made of
a multi-component piezoelectric ceramic material having a perovskite structure composed of
many kinds of metal elements, such as PZT, for example. It is characterized in that the
piezoelectric h constant is inclined and the inclination of the piezoelectric h constant is optimized
so that the piezoelectric h constant becomes maximum on the other surface facing the constant
zero. In the present invention, the piezoelectric h constant means the piezoelectric h33 constant.
The method of tilting the piezoelectric h constant of the piezoelectric plate of the present
invention is as follows: distance x in the thickness direction from the plane where the
piezoelectric h constant is zero is the horizontal axis, and piezoelectric h constant h (x) at that
point The vertical axis represents the relationship between x.sub.2 and h (x) as a straight line or a
curve (hereinafter referred to as "h (x) curve"). In the graph represented by), at least all the
following conditions (1) to (4) are satisfied. (1) [img class = “EMIRef” id = “19829203500004”] That is, the area of the portion below the h (x) curve is h (x) = (h (t) / T) equal to or
larger than the area of the portion below the straight line represented by x, (2) in the range of 0
≦ x <t, the value of h (x) is smaller than h (t) (3) In the range of 0 ≦ x <t, the slope dh (x) / dx is
0 or a positive value, and 2 × 10 <13> V / m <2> or less, (4) At least in the range of 0.8t ≦ x <t,
h (x)> (h (t) / t) · x, ie h (x) is always h (x) = (h (t) / t) being above the straight line represented by
x.
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By using such a gradient, it is possible to obtain an ultrasonic pulse having a short amplitude and
a wide frequency characteristic while having a short pulse. FIGS. 1A to 1D show, by way of
example, several patterns of such an h (x) curve in the range of 0.8t ≦ x <t. If all the above
conditions are satisfied, in the range of 0.8t ≦ x <t, the h (x) curve is a curve convex upward like
B, even if it is a straight line like A in FIG. However, it may be a curve convex downward like C, or
a curve which changes like a wave like D. Among these h (x) curves, in the range of 0.8t ≦ x <t, it
is more effective if the area under the h (x) curve is larger, particularly in the h (x) curve of FIG. It
is desirable to be on the straight line A at or above this straight line. If at least the conditions of
(1), (2) and (3) are satisfied, in the range of 0 <x <0.8 t, the h (x) curve is convex upward even
though it is a straight line. It may be a curve, a curve convex downward, or a curve which
repeatedly changes in a wavelike manner. An example of the most preferable inclination is h (x)
not only in the range of 0.8t ≦ x <t but also in the whole range of 0 <x <t, in addition to the
above conditions (1) to (4). It is> (h (t) / t) · x, and increases monotonously to the maximum value
h (t) without decreasing h (x) as x increases. In particular, as shown in FIG. 7, d <2> h (x) / dx <2>
≦ 0 is satisfied when h (x) becomes from zero to the maximum value h (t). That is, it is ideal that
the slope dh (x) / dx of the h (x) curve is large near x = 0 and gradually decreases as x increases,
so that the pulse amplitude is large. Become. Incidentally, no matter how the inclination is
performed, if the inclination dh (x) / dx exceeds 2 × 10 <13> V / m <2>, a large ultrasonic
excitation is generated at this x position. As a force is generated and an ultrasonic pulse is
generated, the time waveform of the obtained ultrasonic wave does not become short pulses. The
inclination of the piezoelectric h constant as described above is referred to as the composition of
the piezoelectric ceramic material, that is, the component metal element (hereinafter referred to
as “component element”). ) Can be obtained by tilting in the thickness direction. That is, the
piezoelectric plate of the present invention is manufactured, for example, as follows using a
multi-component ceramic material powder in which the piezoelectric h constant changes
monotonically with the change of the ratio of the constituent elements.
A plurality of types of ceramic powder having different piezoelectric h constants are layered in
layers so as to obtain a desired gradient, and a layered pressed compact is produced and
sintered. Alternatively, a plurality of green sheets are manufactured using a plurality of types of
ceramic powder having different piezoelectric h constants, and the plurality of green sheets are
laminated in a predetermined order and pressure-bonded so as to obtain a desired inclination,
and sintered at high temperature . In any case, at the boundary between layers having different
piezoelectric h constants, the constituent elements are thermally diffused to each other at the
time of sintering to change the concentration and the composition changes continuously, so the
piezoelectric h constant has a thickness One piezoelectric plate is obtained which is continuously
and arbitrarily inclined in the direction. According to this method, it is possible to easily
manufacture a piezoelectric plate having a smooth slope of the piezoelectric h constant, and to
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use various types of ceramic powder having different piezoelectric h constants, or to make the
layer thickness or green sheet thickness and stacking By changing the order, it is possible to
freely control the degree of inclination of the piezoelectric h constant, which is conventionally
difficult, in accordance with the purpose. As a conventional method of manufacturing the inclined
piezoelectric plate, there is, for example, a method of partially depolarizing by giving a
temperature gradient in the thickness direction of the piezoelectric plate, or a method of bonding
a plurality of ceramic plates having different piezoelectric constants with an adhesive. In the
former, since the temperature gradient in the thickness direction is automatically determined by
the set temperature of both end faces, it is extremely difficult to control the slope of the h
constant according to the purpose, and the industrial value is Low, and the latter does not give an
acoustic continuum. This method is an excellent method that can solve these problems. The
piezoelectric plate of the present invention is manufactured preferably using a plurality of multicomponent piezoelectric ceramic materials containing the same components and different ratios
of constituent elements as raw materials. In general, in such a piezoelectric ceramic material, the
ratio of a specific constituent element and the piezoelectric h constant are often represented by a
specific function including a proportional relationship. Therefore, in order to obtain the target
inclination, in practice, first, the relationship between the ratio of the constituent elements and
the piezoelectric h constant is examined and plotted, and from that relationship, the function that
holds between the two is specified, and the target piezoelectric The composition of the porcelain
powder to be used is selected according to the method of inclination of h constant. The ultrasonic
transducer according to the present invention uses the piezoelectric plate in which the inclination
of the piezoelectric h constant is optimized as the main component. Specifically, for example, an
electrode film is provided on both sides of this piezoelectric plate, and a porcelain plate whose
acoustic impedance is similar to that of the piezoelectric plate is provided as a backing material
on one side, and a sound absorbing material is optionally provided as a main component. Do.
FIG. 2 is a side sectional view showing an example of the structure of the main part of the
ultrasonic transducer of the present invention. The acoustic impedance similar to that of the
piezoelectric plate is one of the piezoelectric plate subjected to polarization processing, an
electrode film formed on one surface of the piezoelectric plate, and an electrode film formed on
the other surface via the electrode film. It is a thing of the structure which has a porcelain plate
as a main component. In FIG. 2, reference numeral 1 denotes a piezoelectric plate (hereinafter
referred to as “tilted piezoelectric plate”) in which the proportions of constituent elements and
the piezoelectric h constant are distributed in a slope as described above. The inclined
piezoelectric plate 1 is polarized in the direction of the arrow P. Reference numerals 2 and 3 are
electrode films formed on both sides of the inclined piezoelectric plate 1, and reference numerals
6 and 6 'are leads and terminals respectively taken out of the electrode films 2 and 3. Reference
numeral 4 denotes a ceramic plate whose acoustic impedance is similar to that of the inclined
piezoelectric plate 1 and is joined to the inclined piezoelectric plate 1 via the electrode film 3.
The piezoelectric h constant of the inclined piezoelectric plate 1 is maximum at a portion in
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contact with the electrode film 2 on the surface, and is zero at a portion in contact with the
electrode film 3. The direction of this tilt may be reversed. The direction of polarization P may be
the direction shown or the opposite direction. The ceramic plate 4 which is a backing material
may be made of any material as long as the acoustic impedance is similar to that of the inclined
piezoelectric plate 1. You may use the ceramic which shows the piezoelectric property of the
same quality as an inclination piezoelectric plate. The porcelain plate 4 may be bonded to the
electrode film 3 with an adhesive, but if there is an adhesive layer with different acoustic
impedance, reflection of ultrasonic waves is likely to occur in that part, so bonding without using
an adhesive Is desirable. As a method of bonding without using an adhesive, for example, there is
a method of firing simultaneously with a tilt piezoelectric plate by a green sheet method. Further,
in the ceramic plate 4, it is preferable that the end on the opposite side of the bonding surface to
the electrode film 3 has a rough finish or a porous structure so that ultrasonic waves are
irregularly reflected. Further, although not shown, a sound absorbing material may be
additionally attached to the porcelain plate 4. The electrode film 3 is desirably a thin metal film
that does not reflect ultrasonic waves, and is bonded to the inclined piezoelectric plate 1 without
using an adhesive so as not to cause a mismatch in acoustic impedance. For example, it is formed
by sputtering, vapor deposition, plating, or a method of co-firing a metal paste film with a tilt
piezoelectric plate. The electrode film 2 may be formed by any method. Besides baking,
sputtering, vapor deposition, plating of metal paste, a metal foil, a metal plate or the like may be
bonded to the inclined piezoelectric plate 1 using an adhesive.
Alternatively, they may be formed by co-firing with the inclined piezoelectric plate. FIG. 3 is a
side sectional view showing another example of the ultrasonic transducer according to the
present invention. In this case, instead of the piezoelectric plate shown in FIG. 2, two inclined
piezoelectric plates whose piezoelectric h constant is inclined in the thickness direction are
interposed through the internal electrode film 5 so that the piezoelectric h constant becomes
largest at the junction of the two. Use one that is joined. That is, two polarized piezoelectric plates
1 ′ and 1 ′ ′ joined via the internal electrode film so that the piezoelectric h constant is
maximized at the junction with the internal electrode film 5, and one of the piezoelectric plates
An acoustic impedance is obtained by bonding the electrode film 3 formed on the surface not
bonded to the internal electrode film of 1 ′ ′ to the surface not bonded to the inner electrode
film 5 of the other piezoelectric plate 1 ′ via the electrode film Is a structure having a
piezoelectric plate and a similar porcelain plate 4 as main components. The internal electrode
film 5 is desirably a thin metal film that does not reflect ultrasonic waves at the bonding surface
with the ceramic, as with the electrode film 3, and is bonded without using an adhesive. With
such a structure, a more sensitive ultrasonic transducer can be obtained. In the ultrasonic
transducer according to the present invention, since the above-described inclined piezoelectric
plate is used, a voltage pulse is applied between the lead and the terminals 6 and 6 ′ to
generate ultrasonic waves, as shown in FIG. In this case, ultrasonic waves are emitted from both
sides of the large piezoelectric constant of the inclined piezoelectric plate 1 in both directions.
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The ultrasonic waves directed to the inside of the ultrasonic transducer are scattered inside the
porcelain plate 4 and are attenuated and annihilated. In the case of FIG. 3, ultrasonic waves are
emitted bidirectionally from the interface of the inclined piezoelectric plates 1 'and 1' '. The
ultrasonic waves directed to the inside of the ultrasonic transducer are scattered, attenuated and
annihilated as in the case of FIG. Ultrasonic waves directed in the opposite direction are emitted
from the surface of the ultrasonic transducer to the outside. At this time, some of the ultrasonic
waves are reflected at the surface and directed to the inside, but they are attenuated and
annihilated in the same manner as the ultrasonic waves directed to the inside from the beginning.
Therefore, short pulse ultrasonic waves with a wide frequency bandwidth can be obtained in
either form. Next, as a preferred production example of the ultrasonic transducer of the present
invention, a method of producing the ultrasonic transducer of FIG. 2 using a green sheet
laminating method will be described. Three types of ceramic powders a, b and c are prepared,
which are made of a PZT-based ceramic material whose piezoelectric h constant changes
monotonically according to changes in the ratio of constituent elements. The ceramic powder a is
a material not exhibiting piezoelectricity, and the ceramic powders b and c are materials
exhibiting piezoelectricity. When the piezoelectric h constants of the ceramic powders b and c
are hb and hc, respectively, hb = 2 / It is 3 · hc.
These porcelain powders a, b and c are appropriately mixed with a resin and a solvent,
respectively, to form a porcelain powder slurry, which is cast on a PET film and then dried to
obtain green sheets 11, 12 and 13, respectively. In addition, a platinum paste for forming an
electrode consisting of platinum powder, a resin, and a solvent is printed on a single green sheet
11 using porcelain powder a in a predetermined shape so that the thickness of the electrode film
after firing is 5 μm. The electrode paste film 14 is formed. These green sheets are stacked and
pressure-bonded as shown in FIG. 4 and then fired at the sintering temperature of the ceramic
powder, and the inclined piezoelectric plate 1, the electrode film 3 and the backing material as
shown in FIG. 2 The sintered body which integrated with the porcelain plate 4 used as this is
obtained. Next, a silver paste composed of, for example, a silver powder, a glass powder, a resin
and a solvent is applied as an electrode paste and baked on the surface of the sintered body 1
opposite to the electrode film 3 of the inclined piezoelectric plate 1. Form The inclined
piezoelectric plate 1 is polarized by applying a DC voltage between the electrode films 2 and 3.
When the end of the ceramic plate 4 is made porous, a green sheet which becomes porous after
firing may be used in a predetermined portion. As such a green sheet, a sheet having a large
number of through holes at an arbitrary position, a sheet in which resin beads or the like are
mixed, and a cavity is generated after firing are known. The electrode film 2 on the surface can
also be formed by printing a metal paste on the green sheet 13 of the outermost layer in advance
and co-firing with the laminate. In the case of simultaneously sintering the piezoelectric plate, the
electrode and the backing material by such a green sheet method, the process is simplified, and
since the acoustic continuity is obtained, the reflection of the ultrasonic wave is less and the
pulse is shortened. There is an advantage to be possible. However, the present invention prevents
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the backing material from being bonded together using a thin adhesive layer as long as the
acoustic continuity is not impaired as in the following examples, and prevents the electrode from
being formed by other methods such as sputtering. is not. EXAMPLE 1 As the porcelain powder,
(1-α) Pb (Ni1 / 3Nb2 / 3) O3-αPb (Zr0.3Ti0.7) O3 system, where α is 0.450 mol, 0.440 mol,
Six powders of 0.420 mol, 0.390 mol, 0.350 mol and 0.300 mol were prepared. Piezoelectric h
constant (V / m) of these ceramic powders and Ti concentration N (wt%) measured using an Xray microanalyzer are plotted against α, and are shown in FIG.
The relationship between the piezoelectric h constant and the Ti concentration N obtained from
this result is shown in FIG. As apparent from FIG. 6, the piezoelectric h constant and the Ti
concentration are in a proportional relationship. Therefore, if the Ti concentration of porcelain is
measured, the inclination of the piezoelectric h constant can be found. 5 parts by weight of an
acrylic resin and 20 parts by weight of an organic solvent mainly composed of terpionele are
mixed with 100 parts by weight of each of the porcelain powders to form a slurry, and a tape
casting method is used to obtain a thickness of about 160 μm Six types of porcelain green
sheets were produced. These six types of green sheets were laminated in the order of large
piezoelectric h constant, and press-bonded in a state of being heated to 120 ° C. Next, this
laminate was degreased at 400 ° C. for 20 hours, and then sintered at a temperature of 1120 °
C. for 4 hours to obtain a piezoelectric plate. The sintered body was processed into a disk having
a diameter of 15 mm and a thickness of 0.7 mm, the upper and lower surfaces were polished to
be mirror surfaces, and a gold electrode film was formed on the entire upper and lower surfaces
by sputtering. After this, a polarization process was performed by applying a DC voltage of 3 kV
for 30 minutes between the electrode films. By scanning the side surface of the obtained
piezoelectric plate with an X-ray microanalyzer, the concentration N of Ti at the distance x in the
thickness direction from the plane of the piezoelectric h constant was measured at intervals of
about 15 μm. The X-ray microanalyzer is a combination of an S-4500 scanning electron
microscope manufactured by Hitachi Ltd. and an energy dispersive X-ray analyzer EMAX-7000
manufactured by Horiba. FIG. 7 is a plot of the result, and the change in the concentration N of Ti
with respect to the distance x is approximately represented by a curve as shown in the figure.
From the relationship between the piezoelectric h constant and the Ti concentration described
above, it is understood that the piezoelectric h constant is distributed in the thickness direction
with a slope like curve E in this piezoelectric plate. A mirror surface of a porcelain plate (backing
material) having a composition of α = 0.300 mol and a thickness of 20 mm, one surface of
which is mirror finished and the other surface of which is rough finished so as to diffusely reflect
ultrasonic waves. The piezoelectric plate was bonded to the side with an adhesive to manufacture
a test ultrasonic transducer. Here, in order to maintain the acoustic continuity between the
piezoelectric plate and the backing material, the adhesive was made to have a thickness of about
0.1 μm or less. A 20 V spike-like negative voltage pulse was applied between the electrode films
to generate an ultrasonic wave, which was emitted into water. Then, the ultrasonic wave emitted
into the water was detected by a hydrophone probe. FIG. 8 shows the time waveform of the
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emitted ultrasonic wave, and in the test ultrasonic transducer of this example, a pair of positive
and negative short ultrasonic pulses with large amplitude was obtained.
The vertical axis is the output voltage of the hydrophone, which is an amount proportional to the
amplitude of the ultrasonic wave. Example 2 (1-α) Pb (Ni1 / 3Nb2 / 3) O3-αPb (Zr0.3Ti0.7) O3
system, α is 0.450 mol, 0.440 mol, 0.400 mol, 0.365 mol Six types of ceramic powder of 0.330
mol and 0.300 mol were used, and six types of ceramic green sheets having a thickness of about
160 μm were produced in the same manner as in Example 1. These green sheets were laminated
in the order of large piezoelectric h constant, and press-bonded at 120 ° C. Subsequently,
degreasing and sintering were performed in the same manner as in Example 1, and the obtained
gradient piezoelectric plate was processed into a disc to form a gold electrode film, followed by
polarization treatment. The concentration N of Ti at a distance x from the plane of the
piezoelectric h constant of 0 of the obtained piezoelectric plate was measured by an X-ray
microanalyzer and plotted in FIG. From this result, the inclination of the piezoelectric h constant
in the thickness direction is approximately represented by a curve such as F. An ultrasonic
transducer was manufactured in the same manner using the inclined piezoelectric plate in place
of the inclined piezoelectric plate of Example 1, and the ultrasonic characteristics were measured,
and the time waveform is shown in FIG. Comparative Example 1 (1-α) Pb (Ni1 / 3Nb2 / 3) O3αPb (Zr0.3Ti0.7) O3 system, α is 0.450 mol, 0.425 mol, 0.396 mol, 0.364 mol Six types of
ceramic powder of 0.334 mol and 0.300 mol were used, and in the same manner as Example 1,
six types of ceramic green sheets having a thickness of about 160 μm were produced. These
green sheets were laminated in the order of large piezoelectric h constant, and press-bonded at
120 ° C. Subsequently, degreasing and sintering were performed in the same manner as in
Example 1, and the obtained gradient piezoelectric plate was processed into a disc to form a gold
electrode film, followed by polarization treatment. The concentration N of Ti at a distance x in the
thickness direction from the plane where the piezoelectric h constant of the obtained
piezoelectric plate is 0 was measured by an X-ray microanalyzer and plotted in FIG. From this
result, the inclination of the piezoelectric h constant in the thickness direction is approximately
represented by a straight line such as G. An ultrasonic transducer was manufactured in the same
manner using the inclined piezoelectric plate in place of the inclined piezoelectric plate of
Example 1, and the ultrasonic characteristics were measured, and the time waveform is shown in
FIG. Comparative Example 2 (1-α) Pb (Ni1 / 3Nb2 / 3) O3-αPb (Zr0.3Ti0.7) O3 system, α is
0.450 mol, 0.395 mol, 0.356 mol, 0.327 mol Six types of ceramic powder of 0.310 mol and
0.300 mol were used, and in the same manner as Example 1, six types of ceramic green sheets
having a thickness of about 160 μm were produced.
These green sheets were laminated in the order of large piezoelectric h constant, and pressbonded at 120 ° C. Subsequently, degreasing and sintering were performed in the same manner
as in Example 1, and the obtained gradient piezoelectric plate was processed into a disc to form a
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gold electrode film, followed by polarization treatment. The concentration of Ti at a distance x in
the thickness direction from the plane where the piezoelectric h constant of the obtained inclined
piezoelectric plate is 0 was measured by an X-ray microanalyzer and plotted in FIG. From this
result, the inclination of the piezoelectric h constant in the thickness direction is approximately
represented by a curve such as H. An ultrasonic transducer was manufactured in the same
manner as in Example 1 using this inclined piezoelectric plate instead of the inclined
piezoelectric plate of the example, and the ultrasonic characteristics were measured, and the time
waveform is shown in FIG. It is apparent from FIGS. 8, 10, 12, and 14 that the amplitude of the
emitted ultrasonic wave is extremely large in the case where the inclined piezoelectric plate of
the present invention is used. According to the piezoelectric plate of the present invention, by
optimizing the slope of the piezoelectric h constant, it is possible to reproducibly generate an
ultrasonic wave of a short pulse having a wide frequency bandwidth and a large amplitude. It is
possible. Further, according to the present invention, it is possible to easily manufacture a
piezoelectric plate having an optimum piezoelectric h constant inclination by an industrially
suitable method. Further, if the ultrasonic transducer of the present invention is used, it is
possible to achieve high resolution of various ultrasonic measurement devices using ultrasonic
echo method and widening of the used frequency band. BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram showing an example of the h (x) curve in a specific range of x of the
piezoelectric plate of the present invention. FIG. 2 is a side sectional view showing an example of
the structure of the main part of the ultrasonic transducer according to the present invention.
FIG. 3 is a side sectional view showing another example of the structure of the main part of the
ultrasonic transducer according to the present invention. FIG. 4 is an explanatory view showing a
method of manufacturing an ultrasonic transducer according to the present invention by a green
sheet method. FIG. 5 is a diagram in which the piezoelectric h constant of the ceramic powder
used in the examples and the Ti concentration N are plotted against α. FIG. 6 is a graph showing
the relationship between the piezoelectric h constant and the Ti concentration N of the ceramic
powder used in Examples. FIG. 7 is a diagram in which Ti concentration N and piezoelectric h
constant at a distance x in a thickness direction of the piezoelectric plate of Example 1 are
plotted. FIG. 8 is a graph showing a time waveform of an ultrasonic pulse emitted from the
ultrasonic transducer of Example 1; FIG. 9 is a diagram in which the Ti concentration N and the
piezoelectric h constant at a distance x in the thickness direction of the piezoelectric plate of
Example 2 are plotted. FIG. 10 is a graph showing a time waveform of ultrasonic pulses emitted
from the ultrasonic transducer of Example 2;
11 is a diagram in which the Ti concentration N and the piezoelectric h constant at a distance x
in the thickness direction of the piezoelectric plate of Comparative Example 1 are plotted. FIG. 12
is a graph showing a time waveform of an ultrasonic pulse emitted from the ultrasonic
transducer of Comparative Example 1. FIG. FIG. 13 is a diagram in which the Ti concentration N
and the piezoelectric h constant at a distance x in the thickness direction of the piezoelectric
plate of Comparative Example 2 are plotted. FIG. 14 is a graph showing a time waveform of an
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ultrasonic pulse emitted from an ultrasonic transducer of Comparative Example 2; [Explanation
of the code] Direction of P polarization 1,1 ', 1 "Inclined piezoelectric plate 2, 3 electrode film 4
Porcelain plate whose acoustic impedance is similar to that of inclined piezoelectric plate Green
sheet of porcelain powder not showing 12 green sheet of ceramic powder showing piezoelectric
property 13 green sheet of other porcelain powder showing piezoelectric property 14 electrode
paste film
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